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Question 1
Correct
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The cutaneous circulation is responsible for the skin's blood supply. Because the skin is not a highly metabolically active tissue with low energy requirements, its blood supply differs from that of other tissues. Instead of capillaries, some of the circulating blood volume in the skin passes through arteriovenous anastomoses (AVAs).Which of the following statements regarding arteriovenous anastomoses is correct?
Your Answer: AVAs are innervated by sympathetic fibres originating from the hypothalamus
Explanation:Short vessels called arteriovenous anastomoses (AVAs) link tiny arteries and veins. They have a large lumen diameter. The strong and muscular walls allow AVAs to completely clog the vascular lumen, preventing blood flow from artery to vein (acting like a sphincter). When the AVAs open, they create a low-resistance connection between arteries and veins, allowing blood to flow into the limbs’ superficial venous plexuses. There is no diffusion of solutes or fluid into the interstitium due to their strong muscle walls.AVAs are densely innervated by adrenergic fibres from the hypothalamic temperature-regulation centre. High sympathetic output occurs at normal core temperatures, inducing vasoconstriction of the AVAs and blood flow through the capillary networks and deep plexuses. When the temperature rises, sympathetic output decreases, producing AVA vasodilation and blood shunting from the artery to the superficial venous plexus. Heat is lost to the environment as hot blood rushes near to the skin’s surface.AVAs are a specialized anatomical adaptation that can only be found in large quantities in the fingers, palms, soles, lips, and pinna of the ear.
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This question is part of the following fields:
- Cardiovascular Physiology
- Physiology
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Question 2
Correct
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What is the main mechanism of action of dobutamine as an inotropic sympathomimetic:
Your Answer: Beta1-receptor agonist
Explanation:Dobutamine directly stimulates the beta1-adrenergic receptors in the heart and increases contractility and cardiac output with little effect on the rate. In addition action on beta2-receptors causes vasodilation.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 3
Correct
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Which of the following is a physiological function that is mediated by a hormone released by the posterior pituitary:
Your Answer: Water retention
Explanation:Antidiuretic hormone (ADH), released by the posterior pituitary, acts on the kidneys to increase water permeability in the distal nephron allowing greater water reabsorption and concentration of urine. Prolactin, from the anterior pituitary, is responsible for milk production. The thyroid hormones, from the thyroid gland, are responsible for an increase in basal metabolic rate (stimulated by TSH from the anterior pituitary). FSH/LH, from the anterior pituitary, are responsible for maturation of egg and sperm. Calcitonin, from the thyroid gland, is responsible for decreasing calcium levels.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 4
Correct
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You've been asked to give a discussion to a group of medical students about skeletal muscle physiology and its use in clinical medicine. They pose a series of difficult questions to you.Which of the following definitions for the A-band of the sarcomere is correct?
Your Answer: A band that contains the entire length of a single thick filament (myosin)
Explanation:Myofibrils, which are around 1 m in diameter, make up each myofiber. The cytoplasm separates them and arranges them in a parallel pattern along the cell’s long axis. These myofibrils are made up of actin and myosin filaments that are repeated in sarcomeres, which are the myofiber’s basic functional units.Myofilaments are the filaments that make up myofibrils, and they’re made mostly of proteins. Myofilaments are divided into three categories:Myosin filaments are thick filaments made up mostly of the protein myosin.Actin filaments are thin filaments made up mostly of the protein actin.Elastic filaments are mostly made up of the protein titin.The sarcomere is a Z-line segment that connects two adjacent Z-lines.The I-bands are thin filament zones that run from either side of the Z-lines to the thick filament’s beginning.Between the I-bands is the A-band, which spans the length of a single thick filament.The H-zone is a zone of thick filaments that is not overlaid by thin filaments in the sarcomere’s centre. The H-zone keeps the myosin filaments in place by surrounding them with six actin filaments each.The M-band (or M-line) is a disc of cross-connecting cytoskeleton elements in the centre of the H-zone.The thick filament is primarily made up of myosin. The thin filament is primarily made up of actin. Actin, tropomyosin, and troponin are found in a 7:1:1 ratio in thin filaments.
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This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 5
Correct
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At rest, skeletal muscle accounts for between 15-20% of cardiac output and accounts for around 50% of body weight. This can increase to nearly 80% of cardiac output during exercise. Skeletal muscle circulation is highly controlled and has a number of specialized adaptations as a result of this high degree of disparity during exercise, in combination with the diversity in the size of skeletal muscle around the body.What is the primary mechanism for boosting skeletal muscle blood flow during exercise?
Your Answer: Metabolic hyperaemia
Explanation:In skeletal muscle, blood flow is closely related to metabolic rate. Due to the contraction of precapillary sphincters, most capillaries are blocked off from the rest of the circulation at rest and are not perfused. This causes an increase in vascular tone and vessel constriction. As metabolic activity rises, this develops redundancy in the system, allowing it to cope with greater demand. During exercise, metabolic hyperaemia, which is induced by the release of K+, CO2, and adenosine, recruits capillaries. Sympathetic vasoconstriction in the active muscles is overridden by this. Simultaneously, blood flow in non-working muscles is restricted, preserving cardiac output. During exercise, muscle contractions pump blood through the venous system, raising the pressure differential between arterioles and venules and boosting blood flow via capillaries.Capillary angiogenesis is evident when muscles are used repeatedly (e.g. endurance training). It is a long-term effect, not a quick fix for increased blood flow.The local partial pressure of alveolar oxygen is the primary intrinsic control of pulmonary blood flow (pAO2). Low pAO2 promotes arteriole vasoconstriction and vice versa. The hypoxic pulmonary vasoconstriction (HPV) reflex allows blood flow to be diverted away from poorly ventilated alveoli and towards well-ventilated alveoli in order to maximize gaseous exchange.
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This question is part of the following fields:
- Cardiovascular Physiology
- Physiology
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Question 6
Correct
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A 38-year-old woman is investigated for Addison's disease. She had low blood pressure, weakness, weight loss, and skin discoloration. An adrenocorticotropic hormone (ACTH) stimulation test is scheduled as part of her treatment.Which of the following statements about ACTH is correct?
Your Answer: It is released in response to the release of CRH
Explanation:The anterior pituitary gland produces and secretes a peptide hormone called adrenocorticotropic hormone (ACTH) (adenohypophysis). It is secreted in response to the hypothalamus’s secretion of the hormone corticotropin-releasing hormone (CRH).ACTH promotes cortisol secretion via binding to cell surface ACTH receptors in the zona fasciculata of the adrenal cortex.ACTH also promotes the production of beta-endorphin, which is a precursor to melanocyte-releasing hormone (MRH).
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 7
Correct
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A patient who is taking ramipril for high blood pressure complains of a dry persistent cough. What is the mechanism of cough in ACE inhibitor therapy:
Your Answer: Decreased bradykinin breakdown
Explanation:Blocking ACE also diminishes the breakdown of the potent vasodilator bradykinin which is the cause of the persistent dry cough. Angiotensin-II receptor blockers do not have this effect, therefore they are useful alternative for patients who have to discontinue an ACE inhibitor because of persistent cough.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 8
Correct
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What is the mechanism of action of captopril:
Your Answer: Angiotensin-converting enzyme inhibitor
Explanation:Captopril is an angiotensin-converting enzyme (ACE) inhibitor, which inhibits the conversion of angiotensin I to angiotensin II.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 9
Correct
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What is the primary mode of action of Enoxaparin?
Your Answer: Inhibits factor Xa
Explanation:Heparin acts as an anticoagulant by enhancing the inhibition rate of clotting proteases by antithrombin III impairing normal haemostasis and inhibition of factor Xa. Low molecular weight heparins have a small effect on the activated partial thromboplastin time and strongly inhibit factor Xa. Enoxaparin is derived from porcine heparin that undergoes benzylation followed by alkaline depolymerization.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 10
Incorrect
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A 68-year-old man with multiple myeloma presents with complaints of abdominal pain and malaise. A series of blood tests is done and his calcium level is 2.96 mmol/l.What effect will this blood test result have on gastric secretions?
Your Answer: Inhibit the release of intrinsic factor
Correct Answer: Stimulate the release of gastrin
Explanation:Hypercalcaemia stimulates the release of gastrin from the G-cells in the pyloric antrum of the stomach, the duodenum and the pancreas.Gastrin is also released in response to:Stomach distensionVagal stimulationThe presence of amino acids.Gastrin release is inhibited by the presence of acid and somatostatin.
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This question is part of the following fields:
- Gastrointestinal Physiology
- Physiology
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Question 11
Correct
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Discontinuous capillaries are typically found where in the body:
Your Answer: Reticuloendothelial system
Explanation:Discontinuous capillaries, found in the reticuloendothelial system (bone marrow, liver and spleen), have large gaps between endothelial cells and are permeable to red blood cells.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 12
Incorrect
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Which of the following is NOT an adverse effect associated with statin therapy:
Your Answer: Hyperglycaemia
Correct Answer: Aplastic anaemia
Explanation:Adverse effects of statins include:, Headache, Epistaxis, Gastrointestinal disorders (such as constipation, flatulence, dyspepsia, nausea, and diarrhoea), Musculoskeletal and connective tissue disorders (such as myalgia, arthralgia, pain in the extremity, muscle spasms, joint swelling, and back pain), Hyperglycaemia and diabetes, Myopathy and rhabdomyolysis, Interstitial lung disease and Hepatotoxicity
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 13
Correct
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Regarding bile, which of the following statements is CORRECT:
Your Answer: Bile passes into the duodenum through the ampulla of Vater.
Explanation:Bile is synthesised in the liver. Bile functions to eliminate endogenous and exogenous substances from the liver, to neutralise gastric acid in the small intestine, and to emulsify fats in the small intestine and facilitate their digestion and absorption. Bile is stored and concentrated in the gallbladder. Bile passes out of the gallbladder via the cystic duct. Bile passes into the duodenum through the ampulla of Vater regulated by the sphincter of Oddi.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 14
Correct
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Atrial natriuretic peptide (ANP) is primarily produced in response to:
Your Answer: An increase in intravascular fluid volume
Explanation:Atrial natriuretic peptide (ANP) is released from cardiac atrial muscle cells in response to atrial stretch caused by an increase in intravascular fluid volume and is also produced in collecting duct cells.Atrial natriuretic peptide acts to inhibit sodium reabsorption in the distal nephron.
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This question is part of the following fields:
- Physiology
- Renal
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Question 15
Correct
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Regarding diuretics, which of the following statements is CORRECT:
Your Answer: Carbonic anhydrase inhibitors have their effect by inhibiting bicarbonate reabsorption.
Explanation:Carbonic anhydrase inhibitors e.g. acetazolamide block the reaction of carbon dioxide and water and so prevent Na+/H+exchange and bicarbonate reabsorption. The increased bicarbonate levels in the filtrate oppose water reabsorption. Proximal tubule sodium reabsorption is also reduced because it is partly dependent on bicarbonate reabsorption.
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This question is part of the following fields:
- Physiology
- Renal
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Question 16
Correct
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Which of the following does not increase renal phosphate excretion?
Your Answer: Vitamin D
Explanation:PO43-renal excretion is regulated several mechanisms. These include:-parathyroid hormone – increases excretion by inhibiting reabsorption in the proximal tubule-acidosis – increases excretion-glucocorticoids – increases excretion-calcitonin – increases excretion-activated vitamin D – decreases excretion by increasing reabsorption in the distal tubule
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This question is part of the following fields:
- Physiology
- Renal
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Question 17
Correct
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A 54-year-old woman has been visiting her GP with symptoms of tiredness, muscle weakness and headaches. She is known to be hypertensive and takes amlodipine to control this. Her blood results today show that her potassium level is low at 3.0 mmol/L, and her sodium level is slightly elevated at 146 mmol/L.Which of the following is the SINGLE most appropriate INITIAL investigation?
Your Answer: Plasma renin and aldosterone levels
Explanation:Primary hyperaldosteronism occurs when there are excessive levels of aldosterone independent of the renin-angiotensin axis. Secondary hyperaldosteronism occurs due to high renin levels.The causes of primary hyperaldosteronism include:Adrenal adenoma (Conn’s syndrome) – the most common cause of hyperaldosteronism (,80% of all cases). These are usually unilateral and solitary and are more common in women.Adrenal hyperplasia – this accounts for ,15% of all cases. Usually, bilateral adrenal hyperplasia (BAH) but can be unilateral rarely. More common in men than women.Adrenal cancer – a rare diagnosis but essential not to missFamilial aldosteronism – a rare group of inherited conditions affecting the adrenal glandsThe causes of secondary hyperaldosteronism include:Drugs – diureticsObstructive renal artery disease – renal artery stenosis and atheromaRenal vasoconstriction – occurs in accelerated hypertensionOedematous disorders – heart failure, cirrhosis and nephrotic syndromePatients are often asymptomatic. When clinical features are present, the classically described presentation of hyperaldosteronism is with:HypertensionHypokalaemiaMetabolic alkalosisSodium levels can be normal or slightly raisedOther, less common, clinical features include:LethargyHeadachesMuscle weakness (from persistent hypokalaemia)Polyuria and polydipsiaIntermittent paraesthesiaTetany and paralysis (rare)Often the earliest sign of hyperaldosteronism is from aberrant urea and electrolytes showing hypokalaemia and mild hypernatraemia. If the patient is taking diuretics, and the diagnosis is suspected, these should be repeated after the patient has taken off diuretics.If the diagnosis is suspected, plasma renin and aldosterone levels should be checked. Low renin and high aldosterone levels (with a raised aldosterone: renin ratio) is suggestive of primary aldosteronism.If the renin: aldosterone ratio is high, then the effect of posture on renin, aldosterone and cortisol can be investigated to provide further information about the underlying cause of primary hyperaldosteronism. Levels should be measured lying at 9 am and standing at noon:If aldosterone and cortisol levels fall on standing, this is suggestive of an ACTH dependent cause, e.g. adrenal adenoma (Conn’s syndrome)If aldosterone levels rise and cortisol levels fall on standing, this is suggestive of an angiotensin-II dependent cause, e.g. BAHOther investigations that can help to distinguish between an adrenal adenoma and adrenal hyperplasia include:CT scanMRI scanSelective adrenal venous sampling
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 18
Correct
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You examine a 48-year-old patient who has had proximal weakness, hypertension, and easy bruising in the past. She exhibits considerable face fullness and truncal obesity on examination. You diagnose her with Cushing's syndrome.When would her random cortisol level likely be abnormal?
Your Answer: 2400 hrs
Explanation:Cortisol levels fluctuate throughout the day, with the greatest levels occurring around 0900 hours and the lowest occurring at 2400 hrs during sleep.The diurnal swing of cortisol levels is lost in Cushing’s syndrome, and levels are greater throughout the 24-hour period. In the morning, levels may be normal, but they may be high at night-time, when they are generally repressed.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 19
Correct
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Which of the following is NOT a typical electrolyte disturbance caused by furosemide:
Your Answer: Hypercalcaemia
Explanation:Adverse effects of loop diuretics include:Mild gastrointestinal disturbances, pancreatitis and hepatic encephalopathyHyperglycaemiaAcute urinary retentionWater and electrolyte imbalanceHyponatraemia, hypocalcaemia, hypokalaemia, hypomagnesaemia, hypochloraemiaHypotension, hypovolaemia, dehydration, and venous thromboembolismMetabolic alkalosisHyperuricaemiaBlood disorders (bone marrow suppression, thrombocytopenia, and leucopenia)Visual disturbance, tinnitus and deafnessHypersensitivity reactions
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 20
Correct
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Regarding the human cell, which of the following cell organelles is responsible for the production of ATP:
Your Answer: Mitochondria
Explanation:Mitochondria are membrane-bound organelles that are responsible for the production of the cell’s supply of chemical energy. This is achieved by using molecular oxygen to utilise sugar and small fatty acid molecules to generate adenosine triphosphate (ATP). This process is known as oxidative phosphorylation and requires an enzyme called ATP synthase. ATP acts as an energy-carrying molecule and releases the energy in situations when it is required to fuel cellular processes. Mitochondria are also involved in other cellular processes, including Ca2+homeostasis and signalling. Mitochondria contain a small amount of maternal DNA.Mitochondria have two phospholipid bilayers, an outer membrane and an inner membrane. The inner membrane is intricately folded inwards to form numerous layers called cristae. The cristae contain specialised membrane proteins that enable the mitochondria to synthesise ATP. Between the two membranes lies the intermembrane space, which stores large proteins that are required for cellular respiration. Within the inner membrane is the perimitochondrial space, which contains a jelly-like matrix. This matrix contains a large quantity of ATP synthase.Mitochondrial disease, or mitochondrial disorder, refers to a group of disorders that affect the mitochondria. When the number or function of mitochondria in the cell are disrupted, less energy is produced and organ dysfunction results.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 21
Incorrect
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All of the following are indications for beta-blockers EXCEPT for:
Your Answer: Heart failure
Correct Answer: Prinzmetal's angina
Explanation:Beta-blockers are contraindicated in Prinzmetal’s angina.Beta-blockers may be indicated in:HypertensionPheochromocytoma (only with an alpha-blocker)AnginaSecondary prevention after ACSArrhythmias including atrial fibrillationHeart failureThyrotoxicosisAnxietyProphylaxis of migraineEssential tremorGlaucoma
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 22
Incorrect
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The resting membrane potential of a neurone is usually about:
Your Answer: -90 mV
Correct Answer: -70 mV
Explanation:In most neurones the resting potential has a value of approximately -70 mV. The threshold potential is generally around -55 mV. Initial depolarisation occurs as a result of a Na+influx through ligand-gated Na+channels. Action potential is an all or nothing response; because the size of the action potential is constant, the intensity of the stimulus is coded by the frequency of firing of a neuron. Repolarisation occurs primarily due to K+efflux.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 23
Correct
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A patient complains of stomach ache. You see a midline scar in the epigastric area when you examine the abdomen. Upon further interrogation, the patient reveals that she had a subtotal gastrectomy for recurring stomach ulcers several years ago. The stomach mucosa secretes a variety of vital compounds, and her ability to secrete some of these molecules has been harmed as a result of his surgery.The stomach G-cells are responsible for which of the following?
Your Answer: Secretion of gastrin
Explanation:G-cells are a type of cell found in the stomach’s pyloric antrum, duodenum, and pancreas. The secretion of the peptide hormone gastrin is their major function.The table below summarizes the many cell types found in the stomach, as well as the substances secreted by each cell type and the function of the secretion:Cell type/ Substance secreted/ Function of secretionParietal cells/ Hydrochloric acid/ Kills microbes and activates pepsinogenParietal cells/ Intrinsic factor/Binds to vitamin B12 and facilitates its absorptionChief cells/ Pepsinogen/ Protein digestionChief cells/ Gastric lipase/ Fat digestionG-cells/ Gastrin/ Stimulates gastric acid secretionEnterochromaffin-like cells (ECL cells) /Histamine/ Stimulates gastric acid secretionMucous-neck cells/ Mucous and bicarbonate/ Protects stomach epithelium from acidD-cells/ Somatostatin/ Inhibits gastric acid secretion
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This question is part of the following fields:
- Gastrointestinal Physiology
- Physiology
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Question 24
Correct
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Glucagon is the main catabolic hormone of the body and raises the concentration of glucose and fat in the bloodstream.Which pancreatic islet cells secretes glucagon?
Your Answer: Alpha
Explanation:Glucagon, secreted from the pancreatic islet alpha cells, is considered to be the main catabolic hormone of the body. It raises the concentration of glucose and fat in the bloodstreamThere are five different pancreatic islet cells:Alpha cells (20%) – produce glucagonBeta cells (70%) – produce insulin and amylinDelta cells (<10%) – produce somatostatinGamma cells (<5%) – produce pancreatic polypeptideEpsilon cells (<1%) – produce ghrelin
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 25
Correct
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A CT pulmonary angiography of a patient with a massive pulmonary embolus will most likely show which of the following signs?
Your Answer: Increased alveolar dead space
Explanation:A CT pulmonary angiogram is an angiogram of the blood vessels of the lungs. It is a diagnostic imaging test used to check for pulmonary embolism. A pulmonary embolism is caused by a blood clot or thrombus that has become lodged in an artery in the lung and blocks blood flow to the lung. A patient with pulmonary embolism may feel an abrupt onset of pleuritic chest pain, shortness of breath, and hypoxia. Also, pulmonary embolism can result in alveolar dead space. Dead space represents the volume of ventilated air that does not participate in gas exchange. The alveolar dead space is caused by ventilation/perfusion imbalances in the alveoli. It is defined as the sum of the volumes of alveoli that are ventilated but not perfused. Aside from pulmonary embolism, smoking, bronchitis, emphysema, and asthma are among the other causes of alveolar dead space. The other types of dead space are the following: Anatomical dead space is the portion of the airways that conducts gas to the alveoli. This is usually around 150 mL, and there is no possibility of gas exchange in these areas. Physiological dead space is the sum of anatomical and alveolar dead spaces. Physiological dead space can account for up to 30% of the tidal volume.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 26
Incorrect
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A patient has an elevated potassium level of 6.7 mmol/L. All of the following conditions may cause elevated potassium levels, except for which one?
Your Answer: Beta-blockers
Correct Answer: Bartter’s syndrome
Explanation:Bartter’s syndrome is an autosomal recessive renal tubular disorder characterized by hypokalaemia, hypochloraemia, metabolic alkalosis, and hyperreninemia with normal blood pressure. The underlying kidney abnormality results in excessive urinary losses of sodium, chloride, and potassium. Bartter’s syndrome does not cause an elevated potassium level, but instead causes a decrease in its concentration (hypokalaemia). The other choices are causes of hyperkalaemia or elevated potassium levels. Renal failure, Addison’s disease (adrenal insufficiency), congenital adrenal hyperplasia, renal tubular acidosis (type 4), rhabdomyolysis, burns and trauma, tumour syndrome, and acidosis are non-drug causes of hyperkalaemia. On the other hand, drugs that can cause hyperkalaemia include ACE inhibitors, angiotensin receptor blockers, NSAIDs, beta-blockers, digoxin, and suxamethonium.
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This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 27
Correct
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What is the mechanism of action of captopril:
Your Answer: Inhibition of the conversion of angiotensin I to angiotensin II
Explanation:Angiotensin-converting enzyme inhibitors (ACE inhibitors) e.g. captopril inhibit the conversion of angiotensin I to angiotensin II, and thus have a vasodilatory effect, lowering both arterial and venous resistance. The cardiac output increases and, because the renovascular resistance falls, there is an increase in renal blood flow. This latter effect, together with reduced aldosterone release, increases Na+ and H2O excretion, contracting the blood volume and reducing venous return to the heart.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 28
Incorrect
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Regarding the resting membrane potential, which of the following statements is CORRECT:
Your Answer: The resting membrane potential is primarily determined by the Na + equilibrium potential.
Correct Answer: The resting cell membrane is more permeable to K + ions than to Na + ions.
Explanation:A membrane potential is a property of all cell membranes, but the ability to generate an action potential is only a property of excitable tissues. The resting membrane is more permeable to K+and Cl-than to other ions (and relatively impermeable to Na+); therefore the resting membrane potential is primarily determined by the K+equilibrium potential. At rest the inside of the cell is negative relative to the outside. In most neurones the resting potential has a value of approximately -70 mV.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 29
Incorrect
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Regarding haemoglobin, which of the following statements is INCORRECT:
Your Answer: Haem synthesis occurs largely in the mitochondria.
Correct Answer: Haemoglobin synthesis occurs in mature erythrocytes.
Explanation:Haemoglobin is composed of four polypeptide globin chains each with its own iron containing haem molecule. Haem synthesis occurs largely in the mitochondria by a series of biochemical reactions commencing with the condensation of glycine and succinyl coenzyme A under the action of the key rate-limiting enzyme delta-aminolevulinic acid (ALA) synthase. The globin chains are synthesised by ribosomes in the cytosol. Haemoglobin synthesis only occurs in immature red blood cells.There are three types of haemoglobin in normal adult blood: haemoglobin A, A2 and F:- Normal adult haemoglobin (HbA) makes up about 96 – 98 % of total adult haemoglobin, and consists of two alpha (α) and two beta (β) globin chains. – Haemoglobin A2 (HbA2), a normal variant of adult haemoglobin, makes up about 1.5 – 3.5 % of total adult haemoglobin and consists of two α and two delta (δ) globin chains.- Foetal haemoglobin is the main Hb in the later two-thirds of foetal life and in the newborn until approximately 12 weeks of age. Foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin. Red cells are destroyed by macrophages in the liver and spleen after , 120 days. The haem group is split from the haemoglobin and converted to biliverdin and then bilirubin. The iron is conserved and recycled to plasma via transferrin or stored in macrophages as ferritin and haemosiderin. An increased rate of haemoglobin breakdown results in excess bilirubin and jaundice.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 30
Correct
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Regarding platelets, which of the following statements is CORRECT:
Your Answer: Platelets are produced in the bone marrow by fragmentation of the cytoplasm of megakaryocytes.
Explanation:Platelets are produced in the bone marrow by fragmentation of the cytoplasm of megakaryocytes, derived from the common myeloid progenitor cell. The time interval from differentiation of the human stem cell to the production of platelets averages 10 days. Thrombopoietin is the major regulator of platelet formation and 95% of this is produced by the liver. The normal platelet count is approximately 150 – 450 x 109/L and the normal platelet lifespan is 10 days. Under normal circumstances, about one-third of the marrow output of platelets may be trapped at any one time in the normal spleen.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 31
Correct
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Which of the following hormones is dysfunctional in diabetes insipidus:
Your Answer: Antidiuretic hormone
Explanation:Diabetes insipidus (DI) may result from a deficiency of ADH secretion (cranial DI) or from an inappropriate renal response to ADH (nephrogenic DI). As a result, fluid reabsorption at the kidneys is impaired, resulting in large amounts of hypotonic, dilute urine being passed with a profound unquenchable polydipsia.The biochemical hallmarks of DI are:High plasma osmolality (> 295 mOsm/kg)Low urine osmolality (< 300 mOsm/kg)Hypernatraemia (> 145 mmol/L)High urine volume
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 32
Correct
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Pancreatic ductal alkaline fluid secretion is mainly stimulated by which of the following hormones:
Your Answer: Secretin
Explanation:Pancreatic exocrine secretion is controlled by:Parasympathetic stimulation which enhances secretion of both the enzyme and aqueous componentsSympathetic stimulation which inhibits pancreatic secretionSecretin which stimulates secretion of the alkaline-rich fluid from ductal cellsCholecystokinin which stimulates secretion of the enzyme-rich fluid from acinar cellsSomatostatin which inhibits secretion from both acinar and ductal cellsGastrin which stimulates pancreatic acinar cells to secrete digestive enzymes
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 33
Correct
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A 28-year-old patient is intubated and has a central venous catheter inserted after being diagnosed with septic shock. You keep track of her central venous pressure.The normal value for central venous pressure is which of the following?
Your Answer: 0-8 cmH 2 O
Explanation:The pressure measured in the right atrium or superior vena cava is known as central venous pressure (CVP). In a spontaneously breathing subject, the usual CVP value is 0-8 cmH2O (0-6 mmHg).At the conclusion of expiration, the CVP should be measured with the patient resting flat. The catheter’s tip should be at the intersection of the superior vena cava and the right atrium. An electronic transducer is installed and zeroed at the level of the right atrium to measure it (usually in the 4th intercostal space in the mid-axillary line).CVP is a good predictor of preload in the right ventricle. Hypovolaemia is indicated by a volume challenge of 250-500 mL crystalloid eliciting an increase in CVP that is not sustained for more than 10 minutes.CVP is influenced by a number of factors, including:Mechanical ventilation (and PEEP)Pulmonary hypertensionPulmonary embolismHeart failurePleural effusionDecreased cardiac outputCardiac tamponadeCVP is reduced by the following factors:Distributive shockNegative pressure ventilationHypovolaemiaDeep inhalation
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This question is part of the following fields:
- Cardiovascular Physiology
- Physiology
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Question 34
Correct
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Regarding fat digestion, which of the following statements is CORRECT:
Your Answer: Chylomicrons are exocytosed from enterocytes to enter lacteals and thus the lymphatic system.
Explanation:Dietary fat is chiefly composed of triglycerides (esters of free fatty acids and glycerol which may be saturated or unsaturated). The essential fatty acids are linoleic acid and alpha-linoleic acid, which cannot be manufactured in the body. Dietary fat provides 37 kJ (9 kcal) of energy per gram. Fats are digested almost entirely in the small intestine and are only released from the stomach into the duodenum at the rate at which they can be digested.Pancreatic lipase is the most significant enzyme for fat digestion. In the duodenum fat is emulsified by bile acids, a process where larger lipid droplets are broken down into much smaller droplets providing a greater surface area for enzymatic digestion. Micelles are arranged so that hydrophobic lipid molecules lie in the centre, surrounded by bile acids arranged such the outer region is hydrophilic. Dietary and synthesised lipids are incorporated into chylomicrons in the Golgi body, which are exocytosed from the basolateral membrane to enter lacteals and thus the lymphatic system.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 35
Correct
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A 24-year-old athlete drinks a 500 ml hypertonic sports drink before an endurance event he participates in.Which of the following effects will this cause?
Your Answer: The interstitial fluid becomes more concentrated
Explanation:Osmosis is the passive movement of water across a semipermeable membrane from a region of low solute concentration to a region of higher solute concentration.When hypertonic fluid is ingested:The plasma becomes CONCENTRATED. The cells lose water and shrinkThe intracellular fluid becomes more concentrated.Water and ions move freely from the plasma into the interstitial fluid and the interstitial fluid becomes more concentrated. The increased osmotic potential draws water out of the cells.
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This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 36
Incorrect
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Regarding skeletal muscle, which of the following best describes the Z-line:
Your Answer: A line in the middle of the H-zone that holds the myosin filament in position
Correct Answer: A line dividing muscle fibres into sarcomeres
Explanation:Each muscle fibre is divided at regular intervals along its length into sarcomeres separated by Z-lines. The sarcomere is the functional unit of the muscle.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 37
Correct
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Which of the following decreases activation of vitamin D:
Your Answer: Chronic renal failure
Explanation:Calcium deficiency (low Ca2+ diet or hypocalcemia) activates 1-alpha-hydroxylase in the cells of the renal proximal tubule which catalyses the conversion of vitamin D to its active form, 1,25-dihydroxycholecalciferol. Increased parathyroid hormone (PTH) and hypophosphatemia also stimulate the enzyme. Chronic renal failure is associated with a constellation of bone diseases, including osteomalacia caused by failure of the diseased renal tissue to produce the active form of vitamin D.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 38
Incorrect
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Question 39
Correct
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Which of the following statements is correct regarding flow through the cardiovascular system?
Your Answer: Turbulent blood flow may be caused by increased cardiac output.
Explanation:Frictional forces at the sides of a vessel cause a drag force on the fluid touching them in laminar blood flow, which creates a velocity gradient where the flow is greatest at the centre. Laminar blood flow may become disrupted and flow may become turbulent at high velocities, especially in large arteries or where the velocity increases sharply at points of sudden narrowing in the vessels, or across valves. There is increased tendency for thrombi formation when there is turbulent blood flow. Clinically, turbulence may be heard as a murmur or a bruit. As a result of elevated cardiac output, there may be turbulent blood flow, even when the cardiac valves are anatomically normal, and as a result, a physiological murmur can be heard. One such example is pregnancy.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 40
Correct
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Regarding the heart sounds in the cardiac cycle, which of the following statements is INCORRECT:
Your Answer: The third heart sound is caused by filling of an abnormally stiff ventricle in atrial systole.
Explanation:Heart Sound – Phase of Cardiac Cycle – Mechanical Event:First heart sound – Start of systole – Caused by closure of the atrioventricular (mitral & tricuspid) valvesSecond heart sound – End of systole – Caused by closure of the semilunar (aortic and pulmonary) valvesThird heart sound – Early diastole – Caused by rapid flow of blood from the atria into the ventricles during the ventricular filling phaseFourth heart sound – Late diastole – Caused by filling of an abnormally stiff ventricle in atrial systole
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 41
Correct
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Which of the following is NOT a typical effect caused by adrenaline:
Your Answer: Bronchoconstriction
Explanation:Actions of adrenaline:Cardiovascular system- Increased rate and force of cardiac contraction- Vasoconstriction of vessels in skin, mucous membranes and splanchnic bed- Vasodilation of skeletal muscle vessels- Increased cardiac output and blood pressureRespiratory system- Bronchodilation- Increased ventilation rateGastrointestinal system- Smooth muscle relaxation- Contraction of sphincters- Metabolism- Decreased insulin release- Increased glucagon release- Increased thermogenesis- Increased glycolysis- Increased lipolysisEye- Pupillary dilation
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 42
Correct
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The hypothalamus produces antidiuretic hormone (ADH), also known as vasopressin, which is a peptide hormone. It is important for maintaining water and electrolyte balance, as well helping control arterial pressure.To have an effect on blood arteries, ADH binds to which of the following receptors?
Your Answer: V 1 receptor
Explanation:ADH, or antidiuretic hormone, is a hormone that regulates water and electrolyte balance. It is released in response to a variety of events, the most important of which are higher plasma osmolality or lower blood pressure. ADH increases plasma volume and blood pressure via acting on the kidneys and peripheral vasculature.It causes vasoconstriction by binding to peripheral V1 Receptors on vascular smooth muscle via the IP3 signal transduction and Rho-kinase pathways. The systemic vascular resistance and arterial pressure rise as a result. High levels of ADH appear to be required for this to have a major impact on arterial pressure, such as in hypovolaemic shock.
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This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 43
Correct
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Fenestrated capillaries are typically found where in the body:
Your Answer: Renal glomeruli
Explanation:Fenestrated capillaries, found in renal glomeruli, endocrine glands and intestinal villi, are more permeable than continuous capillaries with less tight junctions, and the endothelial cells are also punctured by pores which allow large amounts of fluids or metabolites to pass.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 44
Incorrect
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A 30-year-old woman was involved in a road traffic accident and had a class I haemorrhage.Which physiological parameter is consistent with a diagnosis of class I haemorrhage?
Your Answer: Pulse rate of 115 bpm
Correct Answer: Increased pulse pressure
Explanation:There are 4 classes of haemorrhage. Classification is based on clinical signs and physiological parameters.In CLASS I:Blood loss (ml) is < or = 750Blood loss(% blood volume) < or = 15%Pulse rate (bpm) is 30Pulse pressure is normal or increasedSystolic BP is normalCNS/mental status patient is slightly anxious In CLASS II:Blood loss (ml) is 750 – 1500Blood loss(% blood volume) is 15 – 30%Pulse rate (bpm) is 100 – 120Respiratory rate is 20-30Urine output (ml/hr) is 20-30Pulse pressure is decreasedSystolic BP is normalCNS/mental status patient is mildly anxiousIn CLASS III:Blood loss (ml) is 1500 – 2000Blood loss(% blood volume) is 30- 40%Pulse rate (bpm) is 120 – 140Respiratory rate is 30-40Urine output (ml/hr) is 5-15Pulse pressure is decreasedSystolic BP is decreasedCNS/mental status patient is anxious, confusedIn CLASS IV:Blood loss (ml) is >2000Blood loss(% blood volume) is >40%Pulse rate (bpm) is >140Respiratory rate is >40Urine output (ml/hr) is negligiblePulse pressure is decreasedSystolic BP is decreasedCNS/mental status patient is confused, lethargic
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This question is part of the following fields:
- Cardiovascular Physiology
- Physiology
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Question 45
Correct
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You're evaluating a male patient who's having a lung function test done. In calculating the patient’s functional residual capacity, what parameters should you add to derive the functional residual capacity volume?
Your Answer: Expiratory reserve volume + residual volume
Explanation:The volume of air that remains in the lungs after a single breath is known as functional residual capacity (FRC). It is calculated by combining the expiratory reserve volume and residual volume.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 46
Incorrect
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Regarding hypertensive crises, which of the following statements is CORRECT:
Your Answer: Oral amlodipine is usually first line in management of hypertensive emergencies.
Correct Answer: In a hypertensive emergency, blood pressure should be reduced by 20 - 25% within 2 hours.
Explanation:A hypertensive emergency is defined as severe hypertension (blood pressure ≥ 180/110 mmHg) with acute damage to the target organs. Prompt treatment with intravenous antihypertensive therapy is generally required; over the first few minutes or within 2 hours, blood pressure should be reduced by 20 – 25%. Severe hypertension without acute target organ damage is defined as hypertensive urgency.; blood pressure should be reduced gradually over 24 – 48 hours with oral antihypertensive therapy. If blood pressure is reduced too quickly in the management of hypertensive crises, there is a risk of reduced organ perfusion leading to cerebral infarction, blindness, deterioration in renal function, and myocardial ischaemia.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 47
Correct
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Which of the following drugs is first line treatment for a stable regular broad-complex tachycardia:
Your Answer: Amiodarone
Explanation:A regular broad-complex tachycardia is likely to be ventricular tachycardia or a regular supraventricular rhythm with bundle branch block. A ventricular tachycardia (or broad-complex tachycardia of uncertain origin) should be treated with amiodarone 300 mg IV over 10 – 60 min, followed by an infusion of 900 mg over the next 24 hours. If previously confirmed as SVT with bundle branch block, the patient should be treated as for narrow-complex tachycardia.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 48
Correct
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Myocardial contractility is best correlated with the intracellular concentration of:
Your Answer: Ca2+
Explanation:Contractility of myocardial cells depends on the intracellular [Ca2+], which is regulated by Ca2+entry across the cell membrane during the plateau of the action potential and by Ca2+uptake into and release from the sarcoplasmic reticulum (SR).
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 49
Incorrect
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The arterial blood gas (ABG) of a 56-year-old woman shows type A lactic acidosis.What is the most likely cause of her lactic acidosis?
Your Answer: Renal failure
Correct Answer: Left ventricular failure
Explanation:Lactic acidosis is a common finding in critically ill patients and commonly associated with other serious underlying pathologies. It occurs when pH is 5 mmol/L. Anion gap is increased in lactic acidosis.Acquired lactic acidosis is classified into two subtypes:Type A: lactic acidosis due to tissue hypoxia andType B: due to non-hypoxic processes affecting the production and elimination of lactateSome causes of type A and type B lactic acidosis include:Type A lactic acidosisLeft ventricular failureSevere anaemiaShock (including septic shock)AsphyxiaCardiac arrestCO poisoningRespiratory failureSevere asthma and COPDType B lactic acidosis:Regional hypoperfusionRenal failureLiver failureSepsis (non-hypoxic sepsis)Thiamine deficiencyAlcoholic ketoacidosisDiabetic ketoacidosisCyanide poisoningMethanol poisoningBiguanide poisoning
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This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 50
Correct
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Glomerular filtration rate can be calculated using any substance that:
Your Answer: is freely filtered and neither reabsorbed nor secreted by the nephron
Explanation:Clearance of a substance can provide an accurate estimate of the glomerular filtration rate (GFR) provided that the substance is:freely filterednot reabsorbed in the nephronnot secreted in the nephronnot synthesised or metabolised by the kidney
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This question is part of the following fields:
- Physiology
- Renal
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Question 51
Correct
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Regarding cellular respiration, which of the following statements is CORRECT:
Your Answer: When fats are used as the primary energy source, an excess of acetyl-CoA is produced.
Explanation:Cellular respiration is the process by which cells obtain energy in the form of adenosine triphosphate (ATP). ATP transfers chemical energy from the energy rich substances in the cell to the cell’s energy requiring reactions e.g. active transport, DNA replication and muscle contraction.Cellular respiration is essentially a three step process: 1) Glycolysis, 2)The Krebs cycle, 3)The electron transfer system.The main respiratory substrate used by cells is 6-carbon glucose. Fats and proteins can also be used as respiratory substrates. When fats are being used as the primary energy source, in the absence of glucose, an excess amount of acetyl-CoA is produced, and is converted into acetone and ketone bodies. This can occur in starvation, fasting or in diabetic ketoacidosis. Proteins are used as an energy source only if protein intake is very high, or if glucose and fat sources are depleted.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 52
Correct
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A patient presents to ED with heartburn for which they already take regular antacids. Which of the following drugs can be affected if taken with antacids:
Your Answer: Digoxin
Explanation:Antacids should preferably not be taken at the same time as other drugs since they may affect absorption. When antacids are taken with acidic drugs (e.g. digoxin, phenytoin, chlorpromazine, isoniazid) they cause the absorption of the acidic drugs to be decreased, which causes low blood concentrations of the drugs, which ultimately results in reduced effects of the drugs. Antacids taken with drugs such as pseudoephedrine and levodopa increase absorption of the drugs and can cause toxicity/adverse events due to increased blood levels of the drugs. Antacids that contain magnesium trisilicate and magnesium hydroxide when taken with some other medications (such as tetracycline) will bind to the drugs, and reduce their absorption and effects.
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This question is part of the following fields:
- Gastrointestinal
- Pharmacology
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Question 53
Correct
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A 49-year-old woman has a history of hypertension and persistent hypokalaemia and is diagnosed with hyperaldosteronism.Which of these is the commonest cause of hyperaldosteronism?
Your Answer: Adrenal adenoma
Explanation:When there are excessive circulating levels of aldosterone, hyperaldosteronism occurs. There are two main types of hyperaldosteronism:Primary hyperaldosteronism (,95% of cases)Secondary hyperaldosteronism (,5% of cases)Primary causes of hyperaldosteronism include:Adrenal adenoma (Conn’s syndrome) Adrenal hyperplasiaAdrenal cancerFamilial aldosteronismSecondary causes of hyperaldosteronism include:DrugsObstructive renal artery disease Renal vasoconstrictionOedematous disorders syndrome Adrenal adenoma is the commonest cause of hyperaldosteronism (seen in ,80% of all cases).
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 54
Correct
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Regarding the refractory period, which of the following statements is INCORRECT:
Your Answer: Action potentials can occur in the relative refractory period but the amplitude of the action potential is smaller.
Explanation:Following the action potential, Na+channels remain inactive for a time in a period known as the absolute refractory period where they cannot be opened by any amount of depolarisation. Following this there is a relative refractory period where the temporary hyperpolarisation (due to delayed closure of rectifier K+channels) makes the cell more difficult to depolarise and an action potential can be generated only in response to a larger than normal stimulus. The refractory period limits the frequency at which action potentials can be generated, and ensures that, once initiated, an action potential can travel only in one direction. An action potential is an all or nothing response so the amplitude of the action potential cannot be smaller.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 55
Correct
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A 64-year-old woman with a history of chronic breathlessness is referred for lung function testing.Which of the following statements regarding lung function testing is FALSE? Select ONE answer only.
Your Answer: In restrictive lung disease, the FVC is increased
Explanation:In restrictive lung disorders there is a reduction in the forced vital capacity (FVC) and the forced expiratory volume in one second (FEV1). The decline in the FVC is greater than that of the FEV1, resulting in preservation of the FEV1/FVC ratio (>0.7%).In obstructive lung disease, FEV1is reduced to <80% of normal and FVC is usually reduced but to a lesser extent than FEV1. The FEV1/FVC ratio is reduced to 80% in the presence of symptomsModerate airflow obstruction = FEV1 of 50-79%Severe airflow obstruction = FEV1 of 30-49%Very severe airflow obstruction = FEV1<30%.Spirometry is a poor predictor of durability and quality of life in COPD but can be used as part of the assessment of severity.COPD can only be diagnosed on spirometry if the FEV1 is <80% and FEV1/FVC ratio is < 0.7.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 56
Correct
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A 59-year-old man presents with increased sweating, weight loss, and palpitations. A series of blood tests done found a very low TSH level and a diagnosis of hyperthyroidism is made.What is the commonest cause of hyperthyroidism?
Your Answer: Graves’ disease
Explanation:Hyperthyroidism results from an excess of circulating thyroid hormones. It is commoner in women, and incidence increases with age.Hyperthyroidism can be subclassified into:Primary hyperthyroidism – the thyroid gland itself is affectedSecondary hyperthyroidism – the thyroid gland is stimulated by excessive circulating thyroid-stimulating hormone (TSH).Graves’ disease is the most common cause of hyperthyroidism (estimates are that it causes between 50 and 80% of all cases).Although toxic multinodular goitre, thyroiditis,TSH-secreting pituitary adenoma and drug-induced hyperthyroidism also causes hyperthyroidism, the commonest cause is Graves’ disease.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 57
Incorrect
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Which of the following neurotransmitter and receptor combinations is present at the neuromuscular junction:
Your Answer: Acetylcholine acting at muscarinic receptors
Correct Answer: Acetylcholine acting at nicotinic receptors
Explanation:At the neuromuscular junction, acetylcholine is released from the prejunctional membrane which acts on cholinergic nicotinic receptors on the postjunctional membrane.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 58
Incorrect
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Which of the following hormones regulates Na+reabsorption in the proximal tubule:
Your Answer: Aldosterone
Correct Answer: Angiotensin II
Explanation:Angiotensin II increases Na+reabsorption from the proximal tubule (by activating Na+/H+antiporters).
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This question is part of the following fields:
- Physiology
- Renal
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Question 59
Correct
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Many of the chemical digestion and absorption takes place in the small intestine. Most digestive enzymes in the small intestine are secreted by the pancreas and enter the small intestine through the pancreatic duct.Which of these digestive enzymes is responsible for breaking down carbohydrates into monosaccharides?
Your Answer: Glucoamylase
Explanation:Majority of carbohydrates are broken down into monosaccharides (glucose, fructose galactose) and are absorbed by the small intestine. Enzymes released from the brush border break down carbohydrate. Some carbohydrates, such as cellulose, are not digested at all, despite being made of multiple glucose units. This is because the cellulose is made out of beta-glucose that makes the inter-monosaccharide bindings different from the ones present in starch, which consists of alpha-glucose. Humans lack the enzyme for splitting the beta-glucose-bond.The principal brush border enzymes are dextranase and glucoamylase. Other brush border enzymes are maltase, sucrase, and lactase.Pancreatic amylase breaks down some carbohydrates (notably starch) into oligosaccharides. Dextranase and glucoamylase, then further break down oligosaccharides.Trypsin aids in digestion of protein.Chymotrypsin is a proteolytic enzyme that digests proteinCarboxypeptidase hydrolyses the first peptide or amide bond at the carboxyl or C-terminal end of proteins and peptides
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This question is part of the following fields:
- Gastrointestinal Physiology
- Physiology
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Question 60
Incorrect
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Regarding dynamic compression of the airways, which of the following statements is CORRECT:
Your Answer: It does not occur in normal expiration, because the intrapleural pressure is positive throughout.
Correct Answer: It occurs during forced expiration.
Explanation:Dynamic compression occurs because as the expiratory muscles contract during forced expiration, all the structures within the lungs, including the airways, are compressed by the positive intrapleural pressure. Consequently the smaller airways collapse before the alveoli empty completely and some air remains within the lungs (the residual volume). Physiologically this is important as a completely deflated lung with collapsed alveoli requires significantly more energy to inflate. Dynamic compression does not occur in normal expiration because the intrapleural pressure is negative throughout the whole cycle.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 61
Correct
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A patient with Conn’s syndrome will experience which of the following clinical features?
Your Answer: Hypernatraemia
Explanation:Conditions to consider in the differential diagnosis of primary aldosteronism or Conn’s syndrome include hypertension, metabolic alkalosis, hypokalaemia, hypernatremia, and low renin levels.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 62
Correct
-
Cardiac muscle and skeletal muscle are alike, but there are a few key variations. Which of the following is NOT a characteristic of skeletal muscle but is a characteristic of cardiac muscle?
Your Answer: The presence of intercalated discs
Explanation:Cardiac muscle is striated, and the sarcomere is the contractile unit, similar to skeletal muscle. Contracture is mediated by the interaction of calcium, troponins, and myofilaments, much as it occurs in skeletal muscle. Cardiac muscle, on the other hand, differs from skeletal muscle in a number of ways.In contrast to skeletal muscle cells, cardiac myocytes have a nucleus in the middle of the cell and sometimes two nuclei. The cells are striated because the thick and thin filaments are arranged in an orderly fashion, although the arrangement is less well-organized than in skeletal muscle.Intercalated discs, which work similarly to the Z band in skeletal muscle in defining where one cardiac muscle cell joins the next, are a very significant component of cardiac muscle.Adherens junctions and desmosomes, which are specialized structures that hold the cardiac myocytes together, are formed by the transverse sections. The lateral sections produce gap junctions, which join the cytoplasm of two cells directly, allowing for rapid action potential conduction. These critical properties allow the heart to contract in a coordinated manner, allowing for more efficient blood pumping.Cardiac myocytes have the ability to create their own action potentials, which is referred to as myogenic’. They can depolarize spontaneously to initiate a cardiac action potential. Pacemaker cells, as well as the sino-atrial (SA) and atrioventricular (AV) nodes, control this.The Purkinje cells and the cells of the bundle of His are likewise capable of spontaneous depolarization. While the bundle of His is made up of specialized myocytes, it’s vital to remember that Purkinje cells are not myocytes and have distinct characteristics. They are larger than myocytes, with fewer filaments and more gap junctions than myocytes. They conduct action potentials more quickly, allowing the ventricles to contract synchronously.Cardiac myocytes contract by excitation-contraction coupling, just like skeletal myocytes. Heart myocytes, on the other hand, utilise a calcium-induced calcium release mechanism that is unique to cardiac muscle (CICR). The influx of calcium ions (Ca2+) into the cell causes a ‘calcium spark,’ which causes more ions to be released into the cytoplasm.An influx of sodium ions induces an initial depolarisation, much as it does in skeletal muscle; however, in cardiac muscle, the inflow of Ca2+ sustains the depolarisation, allowing it to remain longer. Due to potassium ion (K+) inflow, CICR causes a plateau phase in which the cells remain depolarized for a short time before repolarizing. Skeletal muscle, on the other hand, repolarizes almost instantly.Comparison of skeletal and cardiac muscle:Skeletal muscle Cardiac muscleStriation Striated but arrangement less organised Multiple nuclei located peripherally Usually single nucleus (but can be two), located centrallyDiscs None Intercalated discsNo Gap junctions Gap junctions No Pacemaker PacemakerElectrical stimulation: Nervous system (excitation) Pacemaker (excitation)
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This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 63
Correct
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A 58-year-old woman presents with symptoms of increase in weight, proximal muscular weakening and withering, easy bruising, and acne. You notice that she has a full, plethoric aspect to her face, as well as significant supraclavicular fat pads, when you examine her. She has previously been diagnosed with Cushing's syndrome.Cushing's syndrome is most commonly caused by which of the following?
Your Answer: Iatrogenic administration of corticosteroids
Explanation:Cushing’s syndrome is a group of symptoms and signs brought on by long-term exposure to high amounts of endogenous or exogenous glucocorticoids. Cushing’s syndrome affects about 10-15 persons per million, and it is more common in those who have had a history of obesity, hypertension, or diabetes.Iatrogenic corticosteroid injection is the most prevalent cause of Cushing’s syndrome. Cushing’s illness is the second most prevalent cause of Cushing’s syndrome. Cushing’s disease is distinct from Cushing’s syndrome in that it refers to a single cause of the illness, a pituitary adenoma that secretes high quantities of ACTH, which raises cortisol levels.Cushing’s syndrome has several endogenous sources, including:Cushing’s disease is caused by a pituitary adenoma.Adrenal adenoma Ectopic corticotropin syndrome, e.g. small cell cancer of the lungAdrenal carcinoma is a cancer of the adrenal gland.Hyperplasia of the adrenal glands
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 64
Correct
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The myocardium is responsible for creating the force with which the atrial and ventricular muscles contract. It is made up of myocytes, which are heart muscle cells.Which of the following statements about cardiac muscle anatomy is correct?
Your Answer: Cardiac myocytes have intercalated discs
Explanation:Typically, granuloma has Langerhan’s cells (large multinucleated cells ) surrounded by epithelioid cell aggregates, T lymphocytes and fibroblasts.Antigen presenting monocytic cells found in the skin are known as Langerhan’s cells.
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This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 65
Incorrect
-
Which of the following is not true regarding the structure and function of glomerular filtration membrane?
Your Answer: Fenestrated capillaries give greater permeability
Correct Answer: The absence of a basement membrane reduces impedance to filtration
Explanation:The glomerular filtration membrane is composed of fenestrated capillary endothelium, basement membrane, and filtration slits. It is an organized, semipermeable membrane preventing the passage of most of the proteins into the urine. The anatomical arrangement of the glomerular filtration membrane maximizes the surface area available for filtration. The arrangement of its arterioles results in high hydrostatic pressures and facilitates filtration. Fenestrated capillary endothelium of the glomerular filtration membrane is with relatively large pores. It allows the free movement of plasma proteins and solutes but still restricts the movement of blood cells. Filtration slits are the smallest filters and restrict the movement of plasma proteins but still allow free movement of ions and nutrients. The glomerular basement membrane (GBM) is a critical component of the glomerular filtration membrane. Thus, it is not true that its absence will reduce the resistance of flow. The basement membrane is true to be more selective and contains negatively charged glycoproteins. However, it still allows free passage of water, nutrients, and ions. Severe structural abnormalities of the GBM can result in protein (albumin) leakage.
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This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 66
Correct
-
A 34-year-old woman was diagnosed with multiple sclerosis two years ago. Her symptoms have been steadily deteriorating, with no intervals of remission in sight.Which of the following aspects of nerve conduction is disrupted by multiple sclerosis?
Your Answer: Saltatory conduction
Explanation:Local currents propagate action potentials down the axons of neurons. This local current flow following depolarisation results in the depolarisation of the neighbouring axonal membrane, and when this region approaches the threshold, more action potentials are generated and so forth. Due to the refractory period, portions of the membrane that have recently depolarized will not depolarize again, resulting in the action potential only being able to go in one direction.The square root of axonal diameter determines the velocity of the action potential; the axons with the biggest diameter have the quickest conduction velocities. When a neuron is myelinated, the speed of the action potential rises as well.The myelin sheath is an insulating coating that surrounds certain neural axons. By increasing membrane resistance and decreasing membrane capacitance, the myelin sheath improves conduction. This enables faster electrical signal transmission via a neuron, making them more energy-efficient than non-myelinated neuronal axons.Electrical impulses are quickly transmitted from one node to the next, causing depolarization of the membrane above the threshold and triggering another action potential, which is then transmitted to the next node. An action potential is rapidly conducted down a neuron in this manner. Saltatory conduction is the term for this.Multiple sclerosis is an example of a clinical disorder in which the myelin sheath is affected. It is an immune-mediated disorder in which certain nerve cells in the brain and spinal cord become demyelinated. The ability of some areas of the nervous system to properly transmit action potentials is disrupted by demyelination, resulting in a variety of neurological symptoms and indications.
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This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 67
Correct
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Cardiac myocytes contract by excitation-contraction coupling, very much like skeletal myocytes. On the other hand, calcium-induced calcium release (CICR) is a mechanism that is unique to Cardiac myocytes. The influx of calcium ions (Ca 2+) into the cell causes a 'calcium spark,' which causes more ions to be released into the cytoplasm.In CICR, which membrane protein in the sarcoplasmic reticulum is involved?
Your Answer: Ryanodine receptor
Explanation:Cardiac myocytes contract by excitation-contraction coupling, just like skeletal myocytes. Heart myocytes, on the other hand, utilise a calcium-induced calcium release mechanism that is unique to cardiac muscle (CICR). The influx of calcium ions (Ca2+) into the cell causes a ‘calcium spark,’ which causes more ions to be released into the cytoplasm.An influx of sodium ions induces an initial depolarisation, much as it does in skeletal muscle; however, in cardiac muscle, the inflow of Ca2+ sustains the depolarisation, allowing it to remain longer. Due to potassium ion (K+) inflow, CICR causes a plateau phase in which the cells remain depolarized for a short time before repolarizing. Skeletal muscle, on the other hand, repolarizes almost instantly.The release of Ca2+ from the sarcoplasmic reticulum is required for calcium-induced calcium release (CICR). This is mostly accomplished by ryanodine receptors (RyR) on the sarcoplasmic reticulum membrane; Ca2+ binds to RyR, causing additional Ca2+ to be released.
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This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 68
Correct
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Pressure across the wall of a flexible tube (the transmural pressure) increases wall tension and extends it.Which law best describes transmural pressure?
Your Answer: Laplace’s law
Explanation:The transmural pressure (pressure across the wall of a flexible tube) can be described by Laplace’s law which states that:Transmural pressure = (Tw) / rWhere:T = Wall tensionw = Wall thicknessr = The radiusA small bubble with the same wall tension as a larger bubble will contain higher pressure and will collapse into the larger bubble if the two meet and join.Fick’s law describes the rate of diffusion in a solutionPoiseuille’s law is used to calculate volume of flow rate in laminar flowDarcy’s law describes the flow of a fluid through a porous medium.Starling’s law describes cardiac haemodynamics as it relates to myocyte contractility and stretch.
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This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 69
Correct
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Which of the following is a primary action of aldosterone:
Your Answer: Renal sodium reabsorption
Explanation:Aldosterone acts mainly at the renal distal convoluted tubule (DCT) to cause sodium retention and potassium loss. It increases the synthesis of transport mechanisms in the distal nephron including the Na+pump, Na+/H+symporter, and Na+and K+channels in principal cells, and H+ATPase in intercalated cells. Na+(and thus water) reabsorption and K+and H+secretion are thereby enhanced.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 70
Correct
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Which of the following is the primary indication for loop diuretics?
Your Answer: Acute pulmonary oedema
Explanation:Loop diuretics have long been the cornerstone of pulmonary oedema treatment, with furosemide being the most commonly used of these drugs. Premedication with drugs that decrease preload (e.g., nitro-glycerine [NTG]) and afterload (e.g., angiotensin-converting enzyme [ACE] inhibitors) before the administration of loop diuretics can prevent adverse hemodynamic changes.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 71
Incorrect
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A 70-year-old patient diagnosed with Cushing's syndrome, has a history of weight gain, hypertension, and easy bruising.Which of the following statements about Cushing's syndrome is NOT true?
Your Answer: Acanthosis nigricans can occur
Correct Answer: Menorrhagia is a common feature
Explanation:Cushing’s syndrome is a group of symptoms and signs brought on by long-term exposure to high amounts of endogenous or exogenous glucocorticoids.Iatrogenic corticosteroid injection is the most prevalent cause of Cushing’s syndrome.Cortisol levels fluctuate throughout the day, with the greatest levels occurring around 0900 hours and the lowest occurring at 2400 hrs during sleep. The diurnal swing of cortisol levels is lost in Cushing’s syndrome, and levels are greater throughout the 24-hour period. In the morning, levels may be normal, but they may be high at night-time, when they are generally repressed.Insulin resistance causes hyperglycaemia, which is a frequent symptom. Insulin resistance can produce acanthosis nigricans in the axilla and around the neck, as well as other skin abnormalities.In contrast to menorrhagia, elevated testosterone levels are more likely to produce amenorrhoea or oligomenorrhoea. Infertility in women of reproductive age can also be caused by high androgen levels.A dexamethasone suppression test or a 24-hour urine free cortisol collection can both be used to establish the existence of Cushing’s syndrome.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 72
Correct
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You are seeing a child with known mitochondrial disease who has presented breathlessness and cough. Which of the following best describes the function of mitochondria:
Your Answer: Energy production
Explanation:Mitochondria are membrane-bound organelles that are responsible for the production of the cell’s supply of chemical energy. This is achieved by using molecular oxygen to utilise sugar and small fatty acid molecules to generate adenosine triphosphate (ATP). This process is known as oxidative phosphorylation and requires an enzyme called ATP synthase. ATP acts as an energy-carrying molecule and releases the energy in situations when it is required to fuel cellular processes. Mitochondria are also involved in other cellular processes, including Ca2+homeostasis and signalling. Mitochondria contain a small amount of maternal DNA.Mitochondria have two phospholipid bilayers, an outer membrane and an inner membrane. The inner membrane is intricately folded inwards to form numerous layers called cristae. The cristae contain specialised membrane proteins that enable the mitochondria to synthesise ATP. Between the two membranes lies the intermembrane space, which stores large proteins that are required for cellular respiration. Within the inner membrane is the perimitochondrial space, which contains a jelly-like matrix. This matrix contains a large quantity of ATP synthase.Mitochondrial disease, or mitochondrial disorder, refers to a group of disorders that affect the mitochondria. When the number or function of mitochondria in the cell are disrupted, less energy is produced and organ dysfunction results.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 73
Correct
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During anaerobic respiration, what is the net generation of ATP molecules:
Your Answer: 2
Explanation:In anaerobic respiration, two ATP molecules are produced for every glucose molecule, as opposed to the 38 molecules of ATP produced in aerobic respiration.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 74
Correct
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Regarding fibrinolytics, which of the following statements is INCORRECT:
Your Answer: Fibrinolytic drugs act as thrombolytics by directly degrading the fibrin mesh and so breaking up thrombi.
Explanation:Fibrinolytic drugs act as thrombolytics by activating plasminogen to form plasmin, which degrades fibrin and so breaks up thrombi.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 75
Correct
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On her most recent blood tests, a 55 year-old female with a history of hypertension was discovered to be hypokalaemic. She is diagnosed with primary hyperaldosteronism.Which of the following is a direct action of aldosterone?
Your Answer: Secretion of H + into the distal convoluted tubule
Explanation:Aldosterone is a steroid hormone produced in the adrenal cortex’s zona glomerulosa. It is the most important mineralocorticoid hormone in the control of blood pressure. It does so primarily by promoting the synthesis of Na+/K+ATPases and the insertion of more Na+/K+ATPases into the basolateral membrane of the nephron’s distal tubules and collecting ducts, as well as stimulating apical sodium and potassium channel activity, resulting in increased sodium reabsorption and potassium secretion. This results in sodium conservation, potassium secretion, water retention, and a rise in blood volume and blood pressure.Aldosterone is produced in response to the following stimuli:Angiotensin II levels have risen.Potassium levels have increased.ACTH levels have risen.Aldosterone’s principal actions are as follows:Na+ reabsorption from the convoluted tubule’s distal endWater resorption from the distal convoluted tubule (followed by Na+)Cl is reabsorbed from the distal convoluted tubule.K+ secretion into the convoluted distal tubule’s H+ secretion into the convoluted distal tubule’s
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This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 76
Incorrect
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What is the recommended dosing regime for amiodarone in the treatment of a stable regular broad-complex tachycardia:
Your Answer: 300 mg IV over 5 minutes, followed by an IV infusion of 900 mg over the next 24 hours
Correct Answer: 300 mg IV over 10 - 60 minutes, followed by an IV infusion of 900 mg over the next 24 hours
Explanation:A ventricular tachycardia (or broad-complex tachycardia of uncertain origin) should be treated with amiodarone 300 mg IV over 10 – 60 min, followed by an infusion of 900 mg over the next 24 hours.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 77
Correct
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Regarding antacids, which of the following statements is CORRECT:
Your Answer: Antacids should not be taken at the same time as other drugs as they impair absorption.
Explanation:Antacids should preferably not be taken at the same time as other drugs since they may impair absorption. Antacids act by neutralising stomach acid. They are used for symptomatic relief in dyspepsia, but are not first line for proven peptic ulcer disease where antisecretory drugs have a better healing effect. Magnesium-containing antacids tend to be laxative whereas aluminium-containing antacids tend to be constipating. Antacids are contraindicated in hypophosphataemia.
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This question is part of the following fields:
- Gastrointestinal
- Pharmacology
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Question 78
Correct
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Mannitol is primarily indicated for which of the following:
Your Answer: Cerebral oedema
Explanation:Mannitol is an osmotic diuretic that can be used to treat cerebral oedema and raised intraocular pressure. Mannitol is a low molecular weight compound and is, therefore, freely filtered at the glomerulus and is not reabsorbed. It, therefore, increases the osmolality of the glomerular filtrate and tubular fluid, increasing urinary volume by an osmotic effect. It also does not cross the blood-brain-barrier (BBB).
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 79
Incorrect
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Which of the following is caused by an alpha-1 antitrypsin deficiency?
Your Answer: Cystic fibrosis
Correct Answer: Early onset emphysema
Explanation:Mucus contains chemicals such as alpha-1-antitrypsin, lysozyme, and IgA that protect the airway from pathogens and damaging proteases released from dead bacteria and immune cells. Early-onset emphysema results from a genetic deficit of alpha-1-antitrypsin, which is caused by unregulated protease activity in the lungs, which results in the degradation of elastin in the alveoli.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 80
Correct
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Osteoclasts are a type of bone cell that are critical in the maintenance, repair and remodelling of bones.Which of the following inhibits osteoclast activity? Select ONE answer only.
Your Answer: Calcitonin
Explanation:Osteoclasts are a type of bone cell that breaks down bone tissue. This is a critical function in the maintenance, repair and remodelling of bones. The osteoclast disassembles and digests the composite of hydrated protein and minerals at a molecular level by secreting acid and collagenase. This process is known as bone resorption and also helps to regulate the plasma calcium concentration.Osteoclastic activity is controlled by a number of hormones:1,25-dihydroxycholecalciferol increases osteoclastic activityParathyroid hormone increases osteoclastic activityCalcitonin inhibits osteoclastic activityBisphosphonates are a class of drug that slow down and prevent bone damage. They are osteoclast inhibitors.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 81
Correct
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A 62-year-old woman presents with cold sensitivity, tiredness, and weight gain. A series of blood tests done shows a grossly elevated TSH level and a diagnosis of hypothyroidism is made.What is the commonest cause of hypothyroidism worldwide?
Your Answer: Iodine deficiency
Explanation:Hypothyroidism occurs when there is a deficiency of circulating thyroid hormones. It is commoner in women and is most frequently seen in the age over 60.Iodine deficiency is the commonest cause of hypothyroidism worldwide.In the UK and other developed countries, iodine deficiency is not a problem and autoimmune thyroiditis is the commonest cause.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 82
Correct
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Depolarisation of a neuron begins with which of the following:
Your Answer: Opening of ligand-gated Na + channels
Explanation:Action potentials are initiated in nerves by activation of ligand-gated Na+channels by neurotransmitters. Opening of these Na+channels results in a small influx of sodium and depolarisation of the negative resting membrane potential (-70 mV). If the stimulus is sufficiently strong, the resting membrane depolarises enough to reach threshold potential (generally around -55 mV), at which point an action potential can occur. Voltage-gated Na+channels open, causing further depolarisation and activating more voltage-gated Na+channels and there is a sudden and massive sodium influx, driving the cell membrane potential to about +40 mV.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 83
Correct
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When the pulmonary artery is completely blocked, what is the ventilation over perfusion ratio for the area that it supplies?
Your Answer: Infinity
Explanation:The ventilation/perfusion ratio (V/Q ratio) is a ratio used to assess the efficiency and adequacy of the matching ventilation and perfusion. A pulmonary artery carries deoxygenated blood from the right side of the heart to the lungs. When a large pulmonary embolus completed blocked a pulmonary artery the alveoli were ventilated but not perfused at all, then the V/Q ratio would be infinity.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 84
Correct
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Water is reabsorbed in which portion of the Henle loop:
Your Answer: Thin descending limb
Explanation:The loop of Henle consists of three functionally distinct segments: the thin descending segment, the thin ascending segment, and the thick ascending segment. About 20 percent of the filtered water is reabsorbed in the loop of Henle and almost all of this occurs in the thin descending limb. Na+ and Cl-ions are actively reabsorbed from the tubular fluid in the thick ascending limb via the Na+/K+/2Cl-symporter on the apical membrane. Because the thick ascending limb is water-impermeable, ion reabsorption lowers tubular fluid osmolality while raising interstitial fluid osmolality, resulting in an osmotic difference. Water moves passively out of the thin descending limb as the interstitial fluid osmolality rises, concentrating the tubular fluid. This concentrated fluid descends in the opposite direction of fluid returning from the deep medulla still higher osmolality areas.
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This question is part of the following fields:
- Physiology
- Renal
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Question 85
Incorrect
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A 36-year-old woman is 22-weeks pregnant and is investigated for a possible thyroid disorder. When her total thyroid hormone levels does not correlate with her thyrometabolic status, her thyroid-binding globulin levels are checked.What percentage of circulating thyroid hormones is bound to thyroid-binding globulin?
Your Answer: 50%
Correct Answer: 70%
Explanation:Only a very small fraction of the thyroid hormones circulating in the blood are free. The majority is bound to transport proteins. Only the free thyroid hormones are biologically active, and measurement of total thyroid hormone levels can be misleading. The relative percentages of bound and unbound thyroid hormones are:Bound to thyroid-binding globulin -70%Bound to albumin -15-20%Bound to transthyretin -10-15%Free T3 -0.3%Free T4 -0.03%
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 86
Correct
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Which of the following is a primary action of calcitonin:
Your Answer: Decreased bone resorption through inhibition of osteoclast activity
Explanation:Calcitonin is a 32 amino acid polypeptide that is primarily synthesised and released by the parafollicular cells (C-cells) of the thyroid gland in response to rising or high levels of plasma Ca2+ions. Its primary role is to reduce the plasma calcium concentration, therefore opposing the effects of parathyroid hormone.Secretion of calcitonin is stimulated by:- Increased plasma calcium concentration- Gastrin- Pentagastrin- The main actions of calcitonin are:- Inhibition of osteoclastic activity (decreasing calcium and phosphate resorption from bone)- Stimulation of osteoblastic activity- Decreases renal calcium reabsorption- Decreases renal phosphate reabsorption
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 87
Correct
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A patient has a cardiac output of 4.8 L/min and a heart rate of 80 bpm, therefore their stroke volume is:
Your Answer: 60 mL
Explanation:Cardiac output (CO) = Stroke volume (SV) x Heart rate (HR). Therefore SV = CO/HR = 4.8/80 = 0.06 L = 60 mL.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 88
Correct
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A 28 year old man presents with abdominal pain and constipation, and bloods show hypocalcaemia. Which of the following hormones is increased as a result of hypocalcaemia?
Your Answer: Parathyroid hormone
Explanation:Parathyroid hormone (PTH), also called parathormone or parathyrin, is a peptide hormone that is secreted by the parathyroid glands, which lie immediately behind the thyroid gland. In particular, this hormone is made by chief cells. It regulates the serum calcium concentration through its effects on bone, kidney, and intestine. This hormone is primarily released in response to decreasing plasma Ca2+ concentration and it serves to increase plasma calcium levels and decrease plasma phosphate levels.PTH activates Ca2+entry channels in the apical membrane and the Ca2+ATPase pump in the basolateral membrane and as a result, increases calcium reabsorption in the distal tubule of the nephron. It inhibits reabsorption of phosphate and this increases its excretion by in the proximal tubule of the nephron.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 89
Correct
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Achlorhydria is diagnosed in a 37-year-old individual who has had recurring episodes of gastroenteritis. This is an autoimmune illness of the gastric parietal cells that causes insufficient stomach acid production.Damage to stomach parietal cells will alter the secretion of which other substance?
Your Answer: Intrinsic factor
Explanation:Achlorhydria is an autoimmune illness of the gastric parietal cells that causes insufficient stomach acid production. The parietal cells that have been injured are unable to create the necessary amount of stomach acid. As a result, the pH of the stomach rises, food digestion suffers, and the risk of gastroenteritis rises.The secretion of hydrochloric acid and intrinsic factor is controlled by the gastric parietal cells, which are epithelial cells in the stomach. These cells can be found in the gastric glands, the fundus lining, and the stomach body.In response to the following three stimuli, the stomach parietal cells release hydrochloric acid:H2 Histamine receptors are stimulated by histamine (most significant contribution)Acetylcholine stimulates M3 Receptors via parasympathetic action.CCK2 receptors are stimulated by Gastrin.Intrinsic factor, which is essential for vitamin B12 absorption, is also produced by stomach parietal cells.Omeprazole is a proton pump inhibitor that is both selective and irreversible. It inhibits the H+/K+-ATPase system present on the secretory membrane of gastric parietal cells, which lowers stomach acid secretion.Ranitidine inhibits histamine H2-receptors in a competitive manner. The reversible inhibition of H2-receptors in gastric parietal cells reduces both the volume and concentration of gastric acid.
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This question is part of the following fields:
- Gastrointestinal Physiology
- Physiology
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Question 90
Correct
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Urine flow rate = 2 ml/minUrine concentration of creatinine = 18 mg/ml Plasma concentration of creatinine = 0.25 mg/ml What is the estimated glomerular filtration rate (eGFR)?
Your Answer: 144 ml/min
Explanation:GFR can be estimated by:GFR = UCr x V / PCrWhere:UCr = urine concentration of creatininePCr = plasma concentration of creatinineV = rate of urine flowIn this case GFR = (18 x 2) / 0.25 = 144 ml/minNote: Creatinine is used to estimate GFR because it is an organic base naturally produced by muscle breakdown, it is freely filtered at the glomerulus, it is not reabsorbed from the nephron, it is not produced by the kidney, it is not toxic, and it doesn’t alter GFR.
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This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 91
Correct
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Which of the following is NOT a mineralocorticoid effect of corticosteroids:
Your Answer: Hyperglycaemia
Explanation:Mineralocorticoid side effects include:hypertensionsodium retentionwater retention and oedemapotassium losscalcium lossGlucocorticoid side effects include:weight gainhyperglycaemia and diabetesosteoporosis and osteoporotic fracturesmuscle wasting (proximal myopathy)peptic ulceration and perforationpsychiatric reactions
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This question is part of the following fields:
- Endocrine
- Pharmacology
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Question 92
Incorrect
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Question 93
Correct
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Regarding conduction of nerve impulses, which of the following statements is CORRECT:
Your Answer: The action potential in myelinated axons is propagated only at the nodes of Ranvier.
Explanation:An action potential is a self-propagating response, successive depolarisation moving along each segment of an unmyelinated nerve until it reaches the end. It is all-or-nothing and does not decrease in size. Conduction in myelinated fibres is much faster, up to 50 times that of the fastest unmyelinated nerve. Myelinated fibres are insulated except at areas devoid of myelin called nodes of Ranvier. The depolarisation jumps from one node of Ranvier to another by a process called saltatory conduction. Saltatory conduction not only increases the velocity of impulse transmission but also conserves energy for the axon because depolarisation only occurs at the nodes and not along the whole length of the nerve fibre. Larger diameter myelinated nerve fibres conduct nerve impulses faster than small unmyelinated nerve fibres.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 94
Correct
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A 58-year-old man showing symptoms of increase in weight, proximal muscular weakening and withering, easy bruising, and acne. You notice that he has a full, plethoric aspect to his face, as well as significant supraclavicular fat pads, when you examine him. His blood pressure is 158/942 mmHg, and his glucose tolerance has lately been impaired. His potassium level is 3.2 mmol/L.What is the MOST LIKELY diagnosis?
Your Answer: Cushing’s syndrome
Explanation:Cushing’s syndrome is a group of symptoms and signs brought on by long-term exposure to high amounts of endogenous or exogenous glucocorticoids. Cushing’s syndrome affects about 10-15 persons per million, and it is more common in those who have had a history of obesity, hypertension, or diabetes.Cushing’s syndrome has a wide range of clinical manifestations that are dependent on the degree of cortisol overproduction. The appearance might be vague and the diagnosis difficult to detect when cortisol levels are just somewhat elevated. On the other hand, in long-term cases of severely increased cortisol levels, the presentation might be colourful and the diagnosis simple.Cushing’s syndrome has the following clinical features:Obesity and weight growth in the true senseSupraclavicular fat pads are fat pads that are located above the clavicle.Buffalo humpFullness and plethora of the face (‘moon facies’)Muscle atrophy and weakening at the proximal levelDiabetes mellitus, also known as impaired glucose toleranceHypertensionSkin thinning and bruisingDepressionHirsutismAcneOsteoporosisAmenorrhoea or oligomenorrhoeaCortisol levels fluctuate throughout the day, with the greatest levels occurring around 0900 hours and the lowest occurring at 2400 hrs during sleep. The diurnal swing of cortisol levels is lost in Cushing’s syndrome, and levels are greater during the whole 24-hour period. In the morning, levels may be normal, but they may be high at night-time, when they are generally repressed. As a result, random cortisol testing is not an effective screening technique and is not advised.The following are the two most common first-line screening tests:Cortisol levels in the urine are measured every 24 hours.A diagnosis of Cushing’s syndrome can be made if more than two collections measure cortisol excretion more than three times the upper limit of normal.Physical stress (e.g., excessive exercise, trauma), mental stress (e.g., sadness), alcohol or drug misuse, complex diabetes, and pregnancy can all cause false positives.Renal dysfunction, inadequate collection, and cyclical Cushing’s disease can all cause false negatives.The overnight low-dose dexamethasone suppression test (LDDST) involves giving 1 mg of dexamethasone at 11 p.m. and measuring blood cortisol levels at 8 a.m. the next day.Cushing’s syndrome is diagnosed when cortisol is not suppressed to less than 50 nmol/L.It might be difficult to tell the difference between mild Cushing’s disease and normal cortisol production.False positives can occur as a result of depression, severe systemic sickness, renal failure, prolonged alcohol misuse, old age, and the use of hepatic enzyme-inducing medicines, among other things.False negatives are extremely uncommon in Cushing’s disease patients.A characteristic biochemical picture might also be helpful in confirming the diagnosis of Cushing’s syndrome. The following are the primary characteristics:HypokalaemiaAlkalosis metabolique
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 95
Correct
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Glucagon is secreted by which of the following pancreatic cell types:
Your Answer: α cells
Explanation:Glucagon is a peptide hormone that is produced and secreted by alpha cells of the islets of Langerhans, which are located in the endocrine portion of the pancreas. The main physiological role of glucagon is to stimulate hepatic glucose output, thereby leading to increases in glycaemia. It provides the major counter-regulatory mechanism to insulin in maintaining glucose homeostasis.Hypoglycaemia is the principal stimulus for the secretion of glucagon but may also be used as an antidote in beta-blocker overdose and in anaphylaxis in patients on beta-blockers that fail to respond to adrenaline. Glucagon then causes:GlycogenolysisGluconeogenesisLipolysis in adipose tissueThe secretion of glucagon is also stimulated by:AdrenalineCholecystokininArginineAlanineAcetylcholineThe secretion of glucagon is inhibited by:InsulinSomatostatinIncreased free fatty acidsIncreased urea productionGlycolysis is the metabolic pathway that converts glucose into pyruvate. The free energy released by this process is used to form ATP and NADH. Glycolysis is inhibited by glucagon, and glycolysis and gluconeogenesis are reciprocally regulated so that when one cell pathway is activated, the other is inactive and vice versa.Glucagon has a minor effect of enhancing lipolysis in adipose tissue. Lipolysis is the breakdown of lipids and involves the hydrolysis of triglycerides into glycerol and free fatty acids. It makes fatty acids available for oxidation.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 96
Incorrect
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A patient in the Emergency Department had a diagnosis of diabetic ketoacidosis (DKA) and you commence an insulin infusion. Which of these statements concerning insulin is true?
Your Answer: Proinsulin is converted to insulin by the removal of a single peptide from the N-terminus
Correct Answer: Insulin has a short half-life of around 5-10 minutes
Explanation:Insulin, a peptide hormone, is produced in the pancreas by the beta-cells of the islets of Langerhans.The beta-cells first synthesise an inactive precursor called preproinsulin which is converted to proinsulin by signal peptidases, which remove a signal peptide from the N-terminus. Proinsulin is converted to insulin by the removal of the C-peptide.Insulin has a short half-life in the circulation of about 5-10 minutes.Glucagon and parasympathetic stimulation stimulates insulin release.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 97
Incorrect
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An infection causes an Addisonian crisis in a male patient with a known history of Addison's disease.Which of the following is NOT a well-known symptom of an Addisonian crisis?
Your Answer: Psychosis
Correct Answer: Hyperglycaemia
Explanation:Although Addisonian crisis is a rare illness, it can be fatal if it is misdiagnosed. Hypoglycaemia and shock are the most common symptoms of an Addisonian crisis (tachycardia, peripheral vasoconstriction, hypotension, altered conscious level, and coma).Other clinical characteristics that may be present are:FeverPsychosisLeg and abdominal painDehydration and vomitingConvulsions
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 98
Correct
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A 30-year-old man bought into the ED with increased thirst, confusion, abdominal pain and constipation is suspected to have hypercalcaemia.What is the commonest cause of hypercalcaemia in the UK?
Your Answer: Primary hyperparathyroidism
Explanation:The commonest cause of hypercalcaemia in the UK is primary hyperparathyroidism, which accounts for around 70-80% of cases. It is commoner in younger patients and in community setting.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 99
Correct
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Which of the following is NOT a function of bile:
Your Answer: Digestion of fats into monoglycerides and fatty acids.
Explanation:Bile functions to eliminate endogenous and exogenous substances from the liver (including bilirubin), to neutralise gastric acid in the small intestine, and to emulsify fats in the small intestine and facilitate their digestion and absorption. Bile salts also act as bactericides, destroying many of the microbes that may be present in the food. Bile doesn’t contain digestive enzymes for digestion of lipids into monoglycerides and fatty acids; this is performed mainly by pancreatic lipase.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 100
Correct
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What is the direct mechanism of action of digoxin as a positive inotrope:
Your Answer: Inhibition of Na+/K+ ATPase pump
Explanation:Digoxin directly inhibits membrane Na+/K+ ATPase, which is responsible for Na+/K+ exchange across the myocyte cell membrane. This increases intracellular Na+ and produces a secondary increase in intracellular Ca2+ that increases the force of myocardial contraction. The increase in intracellular Ca2+ occurs because the decreased Na+ gradient across the membrane reduces the extrusion of Ca2+ by the Na+/Ca2+ exchanger that normally occurs during diastole. Digoxin and K+ ions compete for the receptor on the outside of the muscle cell membrane, and so the effects of digoxin may be dangerously increased in hypokalaemia.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 101
Correct
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A 42-year-old male patient, presenting with polyuria and polydipsia symptoms had normal blood test results. Upon interview, he had mentioned being in a car accident in which he had a head injury. His polyuria and polydipsia symptoms are most likely associated with which of the following conditions?
Your Answer: Cranial diabetes insipidus
Explanation:Polydipsia is the feeling of extreme thirstiness. It is often linked to polyuria, which is a urinary condition that causes a person to urinate excessively. The cycle of these two processes makes the body feel a constant need to replace the fluids lost in urination. In healthy adults, a 3 liter urinary output per day is considered normal. A person with polyuria can urinate up to 15 liters of urine per day. Both of these conditions are classic signs of diabetes. The other options are also types of diabetes, except for psychogenic polydipsia (PPD), which is the excessive volitional water intake seen in patients with severe mental illness or developmental disability. However, given the patient’s previous head injury, the most likely diagnosis is cranial diabetes insipidus. By definition, cranial diabetes insipidus is caused by damage to the hypothalamus or pituitary gland after an infection, operation, brain tumor, or head injury. And the patient’s history confirms this diagnosis. To define the other choices, nephrogenic diabetes insipidus happens when the structures in the kidneys are damaged and results in an inability to properly respond to antidiuretic hormone. Kidney damage can be caused by an inherited (genetic) disorder or a chronic kidney disorder. As with cranial diabetes insipidus, nephrogenic diabetes insipidus can also cause an elevated urine output. Diabetes mellitus is classified into two types, and the main difference between them is that type 1 diabetes is a genetic disorder, and type 2 diabetes is diet-related and develops over time. Type 1 diabetes is also known as insulin-dependent diabetes, in which the pancreas produces little or no insulin. Type 2 diabetes is termed insulin resistance, as cells don’t respond customarily to insulin.
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This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 102
Correct
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Which of the following lifestyle changes is not likely to improve symptoms of gastro-oesophageal reflux disease (GORD):
Your Answer: Lowering the head of the bed
Explanation:The following approaches have some benefit in adult patients with reflux:Weight loss or weight management for individuals who are overweightHead of bed elevation is important for individuals with nocturnal or laryngeal symptoms, but its value for other situations is unclear.The following lifestyle approaches also are used frequently. There is some evidence that these lifestyle changes improve laboratory measures of reflux (such as lower oesophageal sphincter pressure).Dietary modification – A practical approach is to avoid a core group of reflux-inducing foods, including chocolate, peppermint, and alcohol, which may reduce lower oesophageal sphincter pressure. Acidic beverages, including colas with caffeine and orange juice also may exacerbate symptoms. Avoiding the supine position soon after eating.Promotion of salivation by either chewing gum or using oral lozenges. Salivation neutralizes refluxed acid, thereby increasing the rate of oesophageal acid clearance.Avoidance of tobacco (including passive exposure to tobacco smoke) and alcohol. Nicotine and alcohol reduce lower oesophageal sphincter pressure, and smoking also diminishes salivation.
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This question is part of the following fields:
- Gastrointestinal
- Pharmacology
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Question 103
Correct
-
Regarding the partial pressure of gases, which of the following statements is INCORRECT:
Your Answer: At high altitude, the oxygen fraction is reduced.
Explanation:At altitude, the oxygen fraction is unaltered but the barometric pressure and thus partial pressure of oxygen is reduced.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 104
Correct
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A 71-year-old patient has been diagnosed with a dopamine-secreting neuroendocrine tumour.Which of the following statements about dopamine is correct?
Your Answer: It inhibits prolactin release from the anterior pituitary
Explanation:Dopamine is a neurotransmitter and amine hormone that is derived from the amino acid tyrosine. It is made in a number of places throughout the human body, both inside and outside the central nervous system. The adrenal medulla, dopamine neurons in the arcuate nucleus of the hypothalamus, the substantia nigra, and other areas of the brain produce dopamine.The tuberoinfundibular pathway refers to the dopamine neurons in the arcuate nucleus of the hypothalamus’ tubeal region. Dopamine is discharged into the hypothalamo-hypophyseal portal system from these neurons’ neurosecretory terminals at the median eminence.The major function of dopamine produced from the hypothalamus is to suppress prolactin production from the anterior pituitary, and it is released in reaction to excessive levels of prolactin secretion. Modulation of motor-control centres and activation of reward centres are two more crucial activities of the brain.Dopamine-secreting cells can also be found in other areas of the body, where they perform mostly paracrine functions (acting on nearby cells).
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 105
Incorrect
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Which of the following is NOT an adverse effect associated with warfarin therapy:
Your Answer: Calciphylaxis
Correct Answer: Neutropenia
Explanation:Adverse effects of warfarin:The most common adverse effect of warfarin is bleedingOther common adverse effects of warfarin include nausea, vomiting, diarrhoea, jaundice, hepatic dysfunction, pancreatitis, pyrexia, alopecia, purpura, and rashSkin necrosis is a rare but serious adverse effect of warfarin; treatment with warfarin should be stopped if warfarin related skin necrosis is suspectedCalciphylaxis is a rare, but a very serious condition that causes vascular calcification and cutaneous necrosis
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 106
Correct
-
Which of the following states that the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of each of the gases in the mixture:
Your Answer: Dalton's law
Explanation:Dalton’s law states that when two or more gases, which do not react chemically, are present in the same container, the total pressure is the sum of the partial pressures of each gas.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 107
Correct
-
The term cardiac output refers to the amount of blood pumped by the heart in one minute. The rate in women is around 5 L/min, whereas in men is somewhat higher, around 5.5 L/min.Which of the equations below best describes cardiac output?
Your Answer: Stroke volume x heart rate
Explanation:Cardiac output (CO) is calculated by multiplying stroke volume (SV) by heart rate (HR):CO = HR x SVAs a result, both stroke volume and heart rate are exactly proportional to cardiac output. There will be an increase in cardiac output if the stroke volume or heart rate increases, and a reduction in cardiac output if the stroke volume or heart rate lowers.
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This question is part of the following fields:
- Cardiovascular Physiology
- Physiology
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Question 108
Incorrect
-
Which ONE statement about homeostasis is true?
Your Answer: The ‘set point’ is a wide range of values within which normal function occurs
Correct Answer: Negative feedback occurs via receptors, comparators and effectors
Explanation:Homeostasis is the property of a system in which variables are regulated so that internal conditions remain relatively constant and stable. Homeostasis is achieved by a negative feedback mechanism.Negative feedback occurs based upon a set point through receptors, comparators and effectors. The ‘set point’ is a NARROW range of values within which normal function occurs.The two body systems that regulate homeostasis are the Nervous system and the Endocrine system. The smooth muscle of the uterus becomes more active towards the end of pregnancy. This is a POSITIVE feedback.
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This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 109
Correct
-
On which of the following types of receptors does loperamide act?
Your Answer: Opioid receptors
Explanation:Loperamide inhibits acetylcholine release from the myenteric plexus acts by action on opioid mu-receptors, and this then reduces bowel motility. The intestinal transit time is increased, thereby facilitating water reabsorption.
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This question is part of the following fields:
- Gastrointestinal
- Pharmacology
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Question 110
Incorrect
-
Compliance is greater in all but which one of the following:
Your Answer: The base of the lung compared to the apex
Correct Answer: Pulmonary oedema
Explanation:Compliance changes at different lung volumes. Initially at lower lung volumes the compliance of the lung is poor and greater pressure change is required to cause a change in volume. This occurs if the lungs become collapsed for a period of time. At functional residual capacity (FRC) compliance is optimal since the elastic recoil of the lung tending towards collapse is balanced by the tendency of the chest wall to spring outwards. At higher lung volumes the compliance of the lung again becomes less as the lung becomes stiffer. At all volumes, the base of the lung has a greater compliance than the apex. Patients with emphysema have increased compliance. Compliance is affected by a person’s age, sex and height.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 111
Incorrect
-
Regarding pressures and airflow during the normal breathing cycle, which of the following statements is INCORRECT:
Your Answer: In forced expiration, intrapleural pressure becomes positive.
Correct Answer: Negative intrapleural pressure causes dynamic compression of the airways.
Explanation:Dynamic compression occurs during forced expiration, when as the expiratory muscles contract, all the structures within the lungs, including the airways, are compressed by the positive intrapleural pressure. Consequently the smaller airways collapse before the alveoli empty completely and some air remains within the lungs (the residual volume).
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 112
Correct
-
A patient who was put on low molecular weight heparin for suspected DVT and was scheduled for an ultrasound after the weekend, arrives at the emergency department with significant hematemesis. Which of the following medications can be used as a heparin reversal agent:
Your Answer: Protamine sulfate
Explanation:The management of bleeding in a patient receiving heparin depends upon the location and severity of bleeding, the underlying thromboembolic risk, and the current aPTT (for heparin) or anti-factor Xa activity (for LMW heparin). As an example, a patient with minor skin bleeding in the setting of a mechanical heart valve (high thromboembolic risk) and a therapeutic aPTT may continue heparin therapy, whereas a patient with major intracerebral bleeding in the setting of venous thromboembolism several months prior who is receiving heparin bridging perioperatively may require immediate heparin discontinuation and reversal with protamine sulphate. If haemorrhage occurs it is usually sufficient to withdraw unfractionated or low molecular weight heparin, but if rapid reversal of the effects of the heparin is required, protamine sulphate is a specific antidote (but only partially reverses the effects of low molecular weight heparins). Clinician judgment and early involvement of the appropriate consulting specialists is advised.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 113
Incorrect
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In the small intestine, there is a deep gap between each villus that leads to the crypt of Lieberkühn, a tubular intestinal gland.What is the primary function of these glands?
Your Answer: Secretion of gastric-inhibitory peptide
Correct Answer: Production of an alkaline intestinal juice
Explanation:In the small intestine, there is a deep gap between each villus that leads to the crypt of Lieberkühn, a tubular intestinal gland. These glands create an alkaline intestinal juice that is a mixture of water and mucus with a pH of 7.4-7.8. Intestinal juice is released in a volume of 1-2 litres per day in response to distention of the small intestine or the irritating effects of chyme on the intestinal mucosa.
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This question is part of the following fields:
- Gastrointestinal Physiology
- Physiology
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Question 114
Correct
-
Which of the following medications may lessen warfarin's anticoagulant effect:
Your Answer: Phenytoin
Explanation:Phenytoin will decrease the level or effect of warfarin by affecting hepatic/intestinal enzyme CYP3A4 metabolism.Metronidazole will increase the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism.NSAIDs, when given with Warfarin, increase anticoagulation.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 115
Correct
-
Pancreatic acinar digestive enzyme secretion is mainly stimulated by which of the following hormones:
Your Answer: Cholecystokinin
Explanation:Exocrine pancreatic secretion is controlled by:Parasympathetic stimulation which enhances secretion of both the enzyme and aqueous componentsSympathetic stimulation which inhibits pancreatic secretionSecretin which stimulates secretion of the alkaline-rich fluid from ductal cellsCholecystokinin which stimulates secretion of the enzyme-rich fluid from acinar cellsSomatostatin which inhibits secretion from both acinar and ductal cellsGastrin which stimulates pancreatic acinar cells to secrete digestive enzymes
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 116
Correct
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A patient presents with a history of renal problems, generalised weakness and palpitations. Her serum potassium levels are measured and come back at 6.2 mmol/L. An ECG is performed, and it shows some changes that are consistent with hyperkalaemia.Which of the following ECG changes is usually the earliest sign of hyperkalaemia? Select ONE answer only.
Your Answer: Peaked T waves
Explanation:Hyperkalaemia causes a rapid reduction in resting membrane potential leading to increased cardiac depolarisation and muscle excitability. This in turn results in ECG changes which can rapidly progress to ventricular fibrillation or asystole. Very distinctive ECG changes that progressively change as the K+level increases:K+>5.5 mmol/l – peaked T waves (usually earliest sign of hyperkalaemia), repolarisation abnormalitiesK+>6.5 mmol/l – P waves widen and flatten, PR segment lengthens, P waves eventually disappearK+>7.0 mmol/l – Prolonged QRS interval and bizarre QRS morphology, conduction blocks (bundle branch blocks, fascicular blocks), sinus bradycardia or slow AF, development of a sine wave appearance (a pre-terminal rhythm)K+>9.0 mmol/l – Cardiac arrest due to asystole, VF or PEA with a bizarre, wide complex rhythm.
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This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 117
Correct
-
The pathophysiology of Addison's disease is as follows:
Your Answer: Adrenocortical insufficiency
Explanation:Primary adrenal insufficiency, also known as Addison’s disease, occurs when the adrenal glands cannot produce an adequate amount of hormones despite a normal or increased corticotropin (ACTH) level.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 118
Correct
-
Regarding gas exchange at the alveolar-capillary membrane, which of the following statements is CORRECT:
Your Answer: The rate of diffusion in lungs can be estimated by measuring the diffusing capacity of the lungs for carbon monoxide.
Explanation:Gas exchange between alveolar air and blood in the pulmonary capillaries takes place by diffusion across the alveolar-capillary membrane. Diffusion occurs from an area of high partial pressure to an area of low partial pressure, thus the driving force for diffusion is the alveolar-capillary partial pressure gradient. Diffusion occurs across a membrane and is therefore governed by Fick’s law. Although CO2is larger than O2, it is is much more soluble and diffuses 20 times more rapidly. The diffusing capacity for oxygen (DLO2) cannot be measured directly but the rate of diffusion in the lungs can be estimated by measuring the diffusing capacity of the lungs for carbon monoxide (DLCO).
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 119
Correct
-
Which family of receptors does the glucagon receptor belong?
Your Answer: G-protein coupled receptors
Explanation:Glucagon binds to class B G-protein coupled receptors and activates adenylate cyclase, increasing cAMP intracellularly. This activates protein kinase A. Protein kinase A phosphorylates and activates important enzymes in target cells.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 120
Correct
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An arterial blood gas test is performed to a 25-year-old students who presents with confusion, headache, nausea and malaise. The results show that carbon monoxide levels are significantly high. Which of the following carbon monoxide poisoning assertions is true?
Your Answer: The PO 2 of the blood in CO poisoning can be normal
Explanation:By combining with haemoglobin to form carboxyhaemoglobin, carbon monoxide (CO) disrupts the blood’s oxygen transport function. CO binds to haemoglobin with a 240-fold higher affinity than oxygen. As a result, even small amounts of CO can bind a large portion of the blood’s haemoglobin, making it unavailable for oxygen transport. During a suspected carbon monoxide poisoning, the blood PO2 and haemoglobin concentrations will be normal, but the oxygen concentration will be drastically reduced. The oxygen dissociation curve will also shift to the left in the presence of Carboxyhaemoglobin ( haemoglobin and carbon monoxide combination), interfering with oxygen unloading.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 121
Incorrect
-
Which of the following statements is INCORRECT. Fick's law tells us that the rate of diffusion of a gas across a membrane increases as:
Your Answer: the thickness of the cell membrane decreases.
Correct Answer: the partial pressure gradient decreases.
Explanation:Fick’s law tells us that the rate of diffusion of a gas increases: the larger the surface area involved in gas exchangethe greater the partial pressure gradient across the membranethe thinner the membranethe more soluble the gas in the membranethe lower the molecular weight of the gas
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 122
Correct
-
Regarding bile acids, which of the following statements is INCORRECT:
Your Answer: The main primary bile acids are deoxycholic acid and lithocholic acid.
Explanation:Bile acids have a hydrophobic and a hydrophilic end and in aqueous solution, bile salts orient themselves around droplets of lipid forming micelles to keep the lipid droplets dispersed. The principal primary bile acids are cholic acid and chenodeoxycholic acid. They are made more soluble by conjugation with taurine or glycine in the liver. Of the bile acids excreted into the intestine, about 95% are reabsorbed into the portal circulation by active transport mechanisms in the distal ileum and recycled by the liver.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 123
Correct
-
You are reviewing a patient with hypocalcaemia secondary to hypoparathyroidism. Parathyroid hormone (PTH) acts to increased calcium reabsorption at which of the following sites in the nephron:
Your Answer: Distal convoluted tubule
Explanation:Parathyroid hormone (PTH) is a peptide hormone synthesised by the chief cells of the parathyroid glands, located immediately behind the thyroid gland. PTH is primarily released in response to decreasing plasma [Ca2+] concentration. PTH acts to increase plasma calcium levels and decrease plasma phosphate levels.Parathyroid hormone (PTH) acts to increase calcium reabsorption in the distal tubule of the nephron (by activating Ca2+entry channels in the apical membrane and the Ca2+ATPase pump in the basolateral membrane) and increase phosphate excretion by inhibiting reabsorption in the proximal tubule of the nephron.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 124
Correct
-
A 72 year old man is brought to ED by ambulance with sudden onset chest pain, palpitations and shortness of breath. His HR is 160 bpm and BP 90/65. ECG demonstrates new-onset fast atrial fibrillation. Which of the following is the first-line treatment option in this case:
Your Answer: Synchronised DC cardioversion
Explanation:All patients with adverse features suggesting life-threatening haemodynamic instability (shock, syncope, heart failure, myocardial ischaemia) caused by new onset atrial fibrillation should undergo emergency electrical cardioversion with synchronised DC shock without delaying to achieve anticoagulation.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 125
Correct
-
All of the following are indications for beta-blockers EXCEPT for:
Your Answer: Raynaud's disease
Explanation:Beta-blockers are contraindicated in Raynaud’s syndrome. Beta-blockers may be indicated in:HypertensionPheochromocytoma (only with an alpha-blocker)AnginaSecondary prevention after ACSArrhythmias including atrial fibrillationHeart failureThyrotoxicosisAnxietyProphylaxis of migraineEssential tremorGlaucoma
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 126
Correct
-
Which of the following best describes the order in which blood passes through the nephron?
Your Answer: Afferent arteriole→Glomerular capillary→Efferent arteriole→Peritubular capillary→Vasa recta
Explanation:The nephron’s blood flow is as follows:Afferent arteriole – Glomerular capillary – Efferent arteriole – Peritubular capillary – Vasa recta – Afferent arteriole – Glomerular capillary – Efferent arteriole – Peritubular capillary – Vasa rectaThe kidney is the only vascular network in the body with two capillary beds. With arterioles supplying and draining the glomerular capillaries, higher hydrostatic pressures at the glomerulus are maintained, allowing for better filtration. A second capillary network at the tubules enables for secretion and absorption in the tubules, as well as concentrating urine.
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This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 127
Correct
-
Surface area of the absorptive surface in the small intestine is increased by all but which of the following:
Your Answer: Teniae coli
Explanation:Factors increasing the surface area include:The small intestine is very long – about 5 m in length.The inner wall of the small intestine is covered by numerous folds of mucous membrane called plicae circulares.The lining of the small intestine is folded into many finger-like projections called villi.The surface of the villi is covered with a layer of epithelial cells which, in turn, have many small projections called microvilli that project towards the lumen of the intestine (forming the brush border).
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 128
Correct
-
What is the approximate lifespan of the mature erythrocyte:
Your Answer: 120 days
Explanation:Erythrocytes have a normal lifespan of about 120 days. Mature erythrocytes are biconcave discs with no nucleus, ribosomes or mitochondria but with the ability to generate energy as ATP by the anaerobic glycolytic pathway. The red cell membrane consists of a bipolar lipid layer with a membrane skeleton of penetrating and integral proteins anchoring carbohydrate surface antigens. The shape and flexibility of red cells allows them to deform easily and pass through capillaries.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 129
Correct
-
Angiotensin II acts to cause all but which one of the following effects:
Your Answer: Inhibit release of ADH from the posterior pituitary gland
Explanation:Angiotensin II acts to:Stimulate release of aldosterone from the zona glomerulosa of the adrenal cortex (which in turn acts to increase sodium reabsorption)Cause systemic vasoconstrictionCause vasoconstriction of the renal arterioles (predominant efferent effect thus intraglomerular pressure is stable or increased, thereby tending to maintain or even raise the GFR)Directly increase Na+reabsorption from the proximal tubule (by activating Na+/H+antiporters)Stimulate synthesis and release of ADH from the hypothalamus and posterior pituitary respectivelyStimulate the sensation of thirstPotentiate sympathetic activity (positive feedback)Inhibit renin production by granular cells (negative feedback)
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This question is part of the following fields:
- Physiology
- Renal
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Question 130
Incorrect
-
Regarding ACE inhibitors, which of the following statements is CORRECT:
Your Answer: They are recommended first line treatment for hypertension in patients of Afro-Caribbean descent.
Correct Answer: Angiotensin-II receptor blockers are a useful alternative in patients who cannot tolerate ACE-inhibitors due a persistent cough.
Explanation:ACE inhibitors should be used with caution in patients of Afro-Caribbean descent who may respond less well; calcium channel blockers are first line for hypertension in these patients. ACE inhibitors have a role in the management of diabetic nephropathy. ACE inhibitors are contraindicated in pregnant women. ACE inhibitors inhibit the breakdown of bradykinin; this is the cause of the persistent dry cough. Blocking ACE also diminishes the breakdown of the potent vasodilator bradykinin which is the cause of the persistent dry cough. Angiotensin-II receptor blockers do not have this effect, therefore they are useful alternative for patients who have to discontinue an ACE inhibitor because of persistent cough.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 131
Incorrect
-
Which of the following is NOT a typical effect of cortisol:
Your Answer: Increased glycolysis
Correct Answer: Decreased protein catabolism
Explanation:Cortisol is a steroid hormone produced in the zona fasciculata of the adrenal cortex. It is released in response to stress and low blood glucose concentrations.Cortisol acts to: raise plasma glucose by stimulating glycolysis and gluconeogenesis in the liver and inhibiting peripheral glucose uptake into storage tissues, increase protein breakdown in skeletal muscle, skin and bone to release amino acids, increase lipolysis from adipose tissues to release fatty acidsand at higher levels and mimic the actions of aldosterone on the kidney to retain Na+ and water and lose K+ ionssuppress the action of immune cells
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 132
Incorrect
-
A 17-year-old male patient diagnosed with cystic fibrosis is experiencing shortness of breath, coughing, and flu-like symptoms. His X-ray results shows atelectasis, or collapsed lung, specifically in his lower right lung. All of the following statements are true regarding collapsed lungs, except for which one.
Your Answer: Pulmonary capillary blood will have similar PO 2 and PCO 2
Correct Answer: Atelectasis is an example of a perfusion defect
Explanation:Atelectasis is a complete or partial collapse of the lung. It occurs when the alveoli deflate or are filled with alveolar fluid. It is considered a ventilation defect of the alveoli due to cystic fibrosis. It is not a perfusion defect. A perfusion defect will produce pathological dead space in which the lung alveoli are ventilated adequately but are not perfused, and there is no gas exchange. While with atelectasis, the alveoli remain perfused. However, there is impaired oxygen delivery and intrapulmonary shunting of blood will be present in the collapsed area. Since there is no exchange of gas at the capillary-alveolar interface of the collapsed segments, the pulmonary capillary blood will have similar PO2 and PCO2.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 133
Correct
-
What is the effect of a positive inotrope on the Starling curve:
Your Answer: Shifts the curve upwards
Explanation:Contractility (inotropy) is the intrinsic ability of cardiac muscle to develop force at a given muscle length. It is determined by the intracellular [Ca2+] and can be estimated by the ejection fraction. Increases in contractility cause an increase in stroke volume/cardiac output for any level of right atrial pressure or end-diastolic volume, and hence shift the Starling curve upwards. Decreases in contractility cause a decrease in stroke volume/cardiac output for any level of right atrial pressure or end-diastolic volume and hence shift the Starling curve downwards.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 134
Correct
-
The juxtacapillary receptors, or J receptors, are sensory cells that play an important role in the control of respiration.At which of the following anatomical sites are the J receptors located? Select ONE answer only.
Your Answer: The alveolar walls
Explanation:Juxtacapillary receptors (J receptors) are sensory cells that are located within the alveolar walls in juxtaposition to the pulmonary capillaries of the lung.The J receptors are innervated by the vagus nerve and are activated by physical engorgement of the pulmonary capillaries or increased pulmonary interstitial volume, for example, in the presence of pulmonary oedema, pulmonary embolus, pneumonia and barotraumas. They may also be stimulated by hyperinflation of the lung.Stimulation of the J receptors causes a reflex increase in breathing rate and is also thought to be involved in the sensation of dyspnoea. The reflex response that is produced is apnoea, followed by rapid breathing, bradycardia, and hypotension.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 135
Correct
-
Cardiac myocytes are connected to each other by which of the following:
Your Answer: Intercalated discs
Explanation:Adjacent cardiac myocytes are connected to each other by intercalated discs. The intercalated discs provide both a structural attachment by ‘glueing’ cells together at desmosomes and an electrical contact made up of proteins called connexons, called a gap junction, which essentially creates a low-resistance pathway between cells.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 136
Correct
-
Intracellular [Ca2+] rise in cardiac excitation-contraction coupling is mainly as a result of:
Your Answer: Ca 2+ release from sarcoplasmic reticulum
Explanation:Although Ca2+entry during the action potential (AP) is essential for contraction, it only accounts for about 25% of the rise in intracellular Ca2+. The rest is released from Ca2+stores in the sarcoplasmic reticulum (SR). APs travel down invaginations of the sarcolemma called T-tubules, which are close to, but do not touch, the terminal cisternae of the SR. During the AP plateau, Ca2+enters the cell and activates Ca2+sensitive Ca2+release channels in the sarcoplasmic reticulum allowing stored Ca2+to flood into the cytosol; this is called Ca2+-induced Ca2+release. The amount of Ca2+released is dependent on how much is stored, and on the size of the initial Ca2+influx during the AP.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 137
Correct
-
Diabetic ketoacidosis is characterised by which of the following:
Your Answer: Hyperglycaemia, ketonaemia and acidosis
Explanation:DKA is characterised by the biochemical triad:1. Hyperglycaemia (> 11 mmol/L)2. Ketonaemia (> 3 mmol/L)3. Acidosis (pH < 7.3 +/- HCO3 < 15 mmol/L)
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 138
Correct
-
The Frank-Starling curve is shifted downhill in heart failure due to which of the following?
Your Answer: Decrease in contractility
Explanation:The Frank–Starling mechanism states that the left ventricle can increase its force of contraction and hence stroke volume in response to increases in venous return and thus preload. Changes in afterload or inotropy cause the Frank–Starling curve to rise or fall. In heart failure, the Frank–Starling curve is shifted downward (flattened), requiring higher venous return and filling pressure to enhance contractility and stroke volume.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 139
Incorrect
-
When an elderly dehydrated patient is moved from a supine to a standing position, her heart rate increases. Which of the following accounts for the increase in heart rate upon standing:
Your Answer: Increased contractility
Correct Answer: Decreased venous return
Explanation:On standing from a prone position, gravity causes blood to pool in veins in the legs. Central venous pressure (CVP) falls, causing a fall in stroke volume and cardiac output (due to Starling’s law) and thus a fall in blood pressure. Normally this fall in BP is rapidly corrected by the baroreceptor reflex which causes venoconstriction (partially restoring CVP), and an increase in heart rate and contractility, so restoring cardiac output and blood pressure. Impaired autonomic nervous activity in the elderly accounts for the greater likelihood of postural hypotension. Any symptoms of dizziness, blurred vision or syncope is due to a transient fall in cerebral perfusion that occurs before cardiac output and mean arterial pressure (MAP) can be corrected.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 140
Correct
-
A 59-year-old woman presents with a history of tiredness and weight gain and a diagnosis of hypothyroidism is suspected.Which of these changes is likely to appear first in primary hypothyroidism?
Your Answer: Increased thyroid-stimulating hormone (TSH)
Explanation:The earliest biochemical change seen in hypothyroidism is an increase in thyroid-stimulating hormone (TSH) levels.Triiodothyronine (T3) and thyroxine (T4) levels are normal in the early stages.TBG levels are generally unchanged in primary hypothyroidism.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 141
Correct
-
A 70-year-old patient diagnosed with Cushing's syndrome and has a history of weight gain, hypertension, and easy bruising.Which of these assertions about Cushing's syndrome is correct?
Your Answer: Diagnosis can be confirmed by a dexamethasone suppression test
Explanation:Cushing’s syndrome is a group of symptoms and signs brought on by long-term exposure to high amounts of endogenous or exogenous glucocorticoids.Iatrogenic corticosteroid injection is the most prevalent cause of Cushing’s syndrome. Cushing’s illness is the second most prevalent cause of Cushing’s syndrome. Cushing’s disease is distinct from Cushing’s syndrome in that it refers to a single cause of the illness, a pituitary adenoma that secretes high quantities of ACTH, which raises cortisol levels.Because cortisol enhances the vasoconstrictive impact of endogenous adrenaline, patients with Cushing’s syndrome are usually hypertensive.Hyperglycaemia (due to insulin resistance) rather than hypoglycaemia is a common symptom.Cortisol levels fluctuate throughout the day, with the greatest levels occurring around 0900 hours and the lowest occurring at 2400 hrs during sleep. The diurnal swing of cortisol levels is lost in Cushing’s syndrome, and levels are greater throughout the 24-hour period. In the morning, levels may be normal, but they may be high at night-time, when they are generally repressed.A dexamethasone suppression test or a 24-hour urine free cortisol collection can both be used to establish the existence of Cushing’s syndrome.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 142
Correct
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Which of these increases osteoclast activity?
Your Answer: Parathyroid hormone
Explanation:Osteoclasts are bone cell that break down bone tissue. Parathyroid hormone increases osteoclastic activity.1,25-dihydroxycholecalciferol increases osteoclastic activityCalcitonin inhibits osteoclastic activityBisphosphonates are osteoclast inhibitors.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 143
Correct
-
Which of the following globin chains makes up normal adult haemoglobin (HbA)?
Your Answer: Two alpha and two beta chains
Explanation:Total adult haemoglobin comprises about 96 – 98 % of normal adult haemoglobin (HbA). It consists of two alpha (α) and two beta (β) globin chains.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 144
Correct
-
The neurotransmitter in the synaptic cleft is either eliminated or deactivated after the postsynaptic cell responds to the neurotransmitter.Which of the following enzymes catalyses the breakdown of noradrenaline?
Your Answer: Catechol-O-methyltransferase (COMT)
Explanation:The neurotransmitter in the synaptic cleft is either eliminated or deactivated after the post-synaptic cell responds to the neurotransmitter. This can be accomplished in a variety of ways:Re-uptakeBreakdownDiffusionSerotonin is an example of a neurotransmitter that is uptake. Serotonin is absorbed back into the presynaptic neuron via the serotonin transporter (SERT), which is found in the presynaptic membrane. Re-uptake neurotransmitters are either recycled by repackaging into vesicles or broken down by enzymes.Specific enzymes found in the synaptic cleft can also break down neurotransmitters. The following enzymes are examples of these enzymes:Acetylcholinesterase (AChE) catalyses the acetylcholine breakdown (ACh)The enzyme catechol-O-methyltransferase (COMT) catalyses the breakdown of catecholamines like adrenaline , dopamine and noradrenaline. The breakdown of catecholamines, as well as other monoamines like serotonin, tyramine, and tryptamine, is catalysed by monoamine oxidases (MOA).Diffusion of neurotransmitters into nearby locations can also be used to eliminate them.
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This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 145
Correct
-
Regarding bicarbonate handling by the proximal tubule, which of the following statements is CORRECT:
Your Answer: For each H + secreted into the lumen, one Na + and one HCO 3 - is reabsorbed into the plasma.
Explanation:About 80% of bicarbonate is reabsorbed in the proximal tubule. HCO3-is not transported directly, tubular HCO3-associates with H+secreted by epithelial Na+/H+antiporters to form carbonic acid (H2CO3) which readily dissociates to form carbon dioxide and water in the presence of carbonic anhydrase. CO2and water diffuse into the tubular cells, where they recombine to form carbonic acid which dissociates to H+and HCO3-. This HCO3-is transported into the interstitium largely by Na+/HCO3-symporters on the basolateral membrane (and H+is secreted back into the lumen). For each H+secreted into the lumen, one Na+and one HCO3-are reabsorbed into the plasma. H+is recycled so there is little net secretion of H+at this stage.
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This question is part of the following fields:
- Physiology
- Renal
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Question 146
Correct
-
Regarding the cardiac cycle, which of the following statements is INCORRECT:
Your Answer: The second heart sound occurs in late diastole caused by closure of the atrioventricular valves.
Explanation:Diastole is usually twice the length of systole at rest, but decreases with increased heart rate. During systole, contraction of the ventricles compresses the coronary arteries and suppresses blood flow. This is particularly evident in the left ventricle, where during systole the ventricular pressure is the same as or greater than that in the arteries and as a result more than 85% of left ventricular perfusion occurs during diastole. This becomes a problem if the heart rate is increased as the diastolic interval is shorter and can result in ischaemia. The second heart sound, caused by closure of the semilunar valves, marks the end of systole.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 147
Correct
-
A 68-year-old man is being treated with digoxin for atrial fibrillation. When serum digoxin levels are above the therapeutic range, he is at highest risk for developing digoxin toxicity if he also develops which of the following?
Your Answer: Hypokalaemia
Explanation:Predisposing factors for digoxin toxicity include hypoxia, hypercalcaemia, hypokalaemia and hypomagnesaemia There should also be care taken in the elderly who are particularly susceptible to digoxin toxicity. Hypokalaemia may be precipitated by use of diuretics. Hyponatremia can result in the development of other pathological disturbances, but it does not make digoxin toxicity worse.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 148
Correct
-
Which of the following is NOT a typical clinical feature of osteomalacia:
Your Answer: Hypercalcaemia
Explanation:Features of osteomalacia include: Bone pain (particularly bone, pelvis, ribs)Neuromuscular dysfunction (particularly in the gluteal muscles, leading to waddling gaitPseudofractures on x-ray (looser zones)Elevated alkaline phosphatase, hypocalcaemia and low phosphate due to secondary hyperparathyroidism
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 149
Correct
-
Which JVP waveform correlates to atrial systole?
Your Answer: The a wave
Explanation:JVP Waveform in Cardiac Cycle Physiology: a wave Right atrial contraction causes atrial systole (end diastole). the c wave During right isovolumetric ventricular contraction, the tricuspid valve bulges into the right atrium, resulting in isovolumetric contraction (early systole). descent by x Rapid ventricular ejection (mid systole) is caused by a combination of right atrial relaxation, tricuspid valve downward movement during right ventricular contraction, and blood ejection from both ventricles. the v-wave Ventricular ejection and isovolumetric relaxation (late systole) occur as a result of venous return filling the right atrium. y lineage Ventricular filling occurs when the tricuspid valve opens, allowing blood to flow rapidly from the right atrium to the right ventricle.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 150
Correct
-
Which of the following best describes the correct administration of adrenaline for a shockable rhythm in adult advanced life support?
Your Answer: Give 1 mg of adrenaline after the third shock and every 3 - 5 minutes thereafter
Explanation:The correct administration of IV adrenaline 1 mg (10 mL of 1:10,000 solution) is that it should be given after 3 shocks and every 3 – 5 minutes/after alternate shocks thereafter.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 151
Correct
-
The following statements concerning lung compliance is true EXCEPT?
Your Answer: Lung compliance is described by the equation: C = ∆ P/ ∆V, where C = compliance, P = pressure, and V = volume
Explanation:Lung compliance is the change in volume per unit change in distending pressure. It is calculated using the equation:Lung compliance = ΔV / ΔPWhere:ΔV is the change in volumeΔP is the change in pleural pressure.Lung compliance is inversely proportional to stiffness and elastance. It comprises static (no airflow) and dynamic (during continuous breathing) components. It is the slope of the pressure-volume curve.Lung compliance describes the distensibility of the lungs and the chest wall.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 152
Correct
-
Which of the following is NOT a common side effect of amiodarone:
Your Answer: Blue/green teeth discolouration
Explanation:Common side effects of amiodarone include: Bradycardia, Nausea and vomiting, Thyroid disorders – hypothyroidism and hyperthyroidism, Persistent slate grey skin discoloration, Photosensitivity, Pulmonary toxicity (including pneumonitis and fibrosis), Hepatotoxicity, Corneal microdeposits (sometimes with night glare), Peripheral neuropathy and Sleep disorders.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 153
Correct
-
The ECG of a patient presenting with a history of intermittent palpitations has a prolonged QT interval.Which of these can cause prolongation of the QT interval on the ECG?
Your Answer: Hypomagnesaemia
Explanation:The causes of a prolonged QT interval include:HypomagnesaemiaHypothermiaHypokalaemia HypocalcaemiaHypothyroidism Jervell-Lange-Nielsen syndrome (autosomal dominant)Romano Ward syndrome (autosomal recessive)Ischaemic heart diseaseMitral valve prolapseRheumatic carditisErythromycinAmiodaroneQuinidineTricyclic antidepressantsTerfenadineMethadoneProcainamideSotalol
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This question is part of the following fields:
- Cardiovascular Physiology
- Physiology
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Question 154
Correct
-
Antidiuretic hormone (ADH) is synthesised by which of the following:
Your Answer: Hypothalamus
Explanation:Antidiuretic hormone is synthesised in the hypothalamus and transported to the posterior pituitary within nerve fibres where it is stored in secretory granules. ADH binds V2 receptors on renal principal cells in the late distal tubule and collecting ducts, raising cAMP levels and causing intracellular vesicles to fuse with the apical membrane. In their membrane these vesicles have water channels called aquaporins, which increase the water permeability allowing greater water reabsorption and concentration of urine. Excess levels of ADH results in syndrome of inappropriate ADH secretion (SIADH) characterised by hyponatremia with concomitant hypo-osmolality and high urine osmolality.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 155
Incorrect
-
In the extrinsic pathway of the coagulation cascade, the tenase complex is:
Your Answer: Factor IXa-VIIIa complex
Correct Answer: Factor VIIa-tissue factor complex
Explanation:The extrinsic pathway for initiating the formation of prothrombin activator begins with a traumatized vascular wall or traumatized extravascular tissues that come in contact with the blood. Exposed and activated by vascular injury, with plasma factor VII. The extrinsic tenase complex, factor VIIa-tissue factor complex, activates factor X to factor Xa.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 156
Correct
-
Atrial natriuretic peptide (ANP) acts to cause all of the following effects EXCEPT for:
Your Answer: Vasoconstricts the afferent arteriole
Explanation:ANP acts to: Inhibit Na+ reabsorption in the distal nephron (through inhibition of ENaC in principal cells)Suppress the production of reninSuppress the production of aldosteroneSuppress the production of ADHCause renal vasodilation, increasing the glomerular filtration rate
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This question is part of the following fields:
- Physiology
- Renal
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Question 157
Incorrect
-
Antidiuretic hormone (ADH) has which of the following effects:
Your Answer: Increases water retention by increasing sodium reabsorption in the distal convoluted tubule
Correct Answer: Increases urine osmolality
Explanation:ADH binds V2 receptors on renal principal cells in the late distal tubule and collecting ducts, raising cAMP levels and causing intracellular vesicles to fuse with the apical membrane. In their membrane these vesicles have water channels called aquaporins, which increase the water permeability allowing greater water reabsorption and concentration of urine. ADH also binds to V1 receptor receptors on vascular smooth muscle, causing vasoconstriction and enhancing the effect of aldosterone on sodium reabsorption in the distal tubule. ADH release is stimulated primarily by raised plasma osmolality detected by osmoreceptors in the anterior hypothalamus. Other factors that increase ADH release include: extracellular fluid volume depletion, angiotensin II, nausea, pain, stress, exercise, emotion, hypoglycaemia. ADH release is inhibited by low plasma osmolality, alcohol, caffeine, glucocorticoids and atrial natriuretic peptide (ANP). ADH deficiency (or an inadequate response to ADH) results in diabetes insipidus. Excess levels of ADH results in syndrome of inappropriate ADH secretion (SIADH).
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 158
Incorrect
-
Which of the following statements is correct with regards to heparin-induced thrombocytopaenia (HIT)?
Your Answer: Further anticoagulation should be avoided until HIT has resolved.
Correct Answer: HIT typically develops 5-10 days after starting heparin.
Explanation:Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder caused by antibodies that recognize complexes of platelet factor 4 (PF4) and heparin. HIT is frequently considered in the differential diagnosis of thrombocytopenia occurring in patients on heparin therapy. HIT is a challenging diagnosis because of routine heparin use in hospitalized patients, the common occurrence of thrombocytopenia. The process of heparin dependent IgG antibodies binding to heparin/platelet factor 4 complexes activates platelets and produces a hypercoagulable state. This syndrome typically develops 5-10 days (range 4-15 days) after heparin is commenced. It can occur with unfractionated heparin, low molecular weight heparin, or, rarely, fondaparinux. The diagnosis of HIT requires the combination of a compatible clinical picture and laboratory confirmation of the presence of heparin dependent platelet activating HIT antibodies. Discontinuation of heparin alone or initiation of a vitamin K antagonist alone like warfarin, is not sufficient to stop the development of thrombosis in patients with acute HIT. If there is moderate clinical suspicion for HIT, all sources of heparin must be discontinued and there must be consideration of anticoagulant treatment with a non-heparin drug.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 159
Correct
-
The following all cause a right shift in the oxygen dissociation curve EXCEPT for:
Your Answer: Foetal haemoglobin
Explanation:A decreased affinity of haemoglobin for oxygen (and hence increased ease of dissociation), shown by a right shift in the oxygen dissociation curve, is caused by a fall in pH, a rise in PCO2(the Bohr effect) and an increase in temperature. These changes occur in metabolically active tissues such as in exercise, and encourage oxygen release. The metabolic by-product 2,3-diphosphoglycerate (2,3 -DPG) also causes a right shift; 2, 3 -DPG may also be raised in chronic anaemia, chronic lung disease, or at high altitude. Foetal haemoglobin (HbF) binds 2, 3 -DPG less strongly than does adult haemoglobin (HbA), and so the HbF dissociation curve lies to the left of that for HbA, reflecting its higher oxygen affinity. This helps transfer oxygen from mother to foetus.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 160
Correct
-
What is the main mechanism of action of flecainide:
Your Answer: Blocks Na+ channels
Explanation:Flecainide inhibits the transmembrane influx of extracellular Na+ ions via fast channels on cardiac tissues resulting in a decrease in rate of depolarisation of the action potential, prolonging the PR and QRS intervals. At high concentrations, it exerts inhibitory effects on slow Ca2+ channels, accompanied by moderate negative inotropic effect.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 161
Incorrect
-
Regarding transport across a membrane, which of the following statements is CORRECT:
Your Answer: Diffusion is the passive movement of molecules across a membrane from an area of low concentration to an area of high concentration.
Correct Answer: Ion channels may be voltage-gated or ligand-gated.
Explanation:Diffusion is the passive movement of ions across a cell membrane down their electrochemical or concentration gradient through ion channels. Ion channels can be voltage-gated (regulated according to the potential difference across the cell membrane) or ligand-gated (regulated by the presence of a specific signal molecule). Facilitated diffusion is the process of spontaneous passive transport of molecules or ions down their concentration gradient across a cell membrane via specific transmembrane transporter (carrier) proteins. The energy required for conformational changes in the transporter protein is provided by the concentration gradient rather than by metabolic activity. In secondary active transport there is no direct coupling of ATP but the initial Na+ electrochemical gradient that drives the secondary active transport is set up by a process that requires metabolic energy. Examples include the sodium/calcium exchanger, or the sodium/glucose symporter.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 162
Incorrect
-
You evaluate a 80-year-old man who has a history of persistent heart failure and discover that he has generalised oedema.Which of the following claims regarding capillary hydrostatic pressure (P c) is false?
Your Answer: P c is more sensitive to changes in venule pressure than arteriolar pressure
Correct Answer: P c increases along the length of the capillary, from arteriole to venule
Explanation:The capillary hydrostatic pressure (Pc) is normally between 15 and 30 millimetres of mercury. Pc Decreases along the capillary’s length, mirroring the arteriolar and venule pressures proximally and distally.Pc is determined by the ratio of arteriolar resistance (RA) to venular resistance (RV).When the RA/RV ratio is high, the pressure drop across the capillary is modest, and Pcis is close to venule pressure.When the ratio of RA/RV is low, the pressure drop across the capillary is considerable, and Pcis is close to arteriolar pressure.Pcis closer to the venule pressure and thus more responsive to changes in venous pressure than arteriolar pressure when RA/RV is high.Pcis the major force behind fluid pushing out of the capillary bed and into the interstitium.It is also the most variable of the forces affecting fluid transport at the capillary, partly because sympathetic-mediated arteriolar vasoconstriction varies.
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This question is part of the following fields:
- Cardiovascular Physiology
- Physiology
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Question 163
Correct
-
Alpha cells of the endocrine pancreas produce which of the following hormones:
Your Answer: Glucagon
Explanation:Glucagon is a peptide hormone that is produced and secreted by alpha cells of the islets of Langerhans, which are located in the endocrine portion of the pancreas. The main physiological role of glucagon is to stimulate hepatic glucose output, thereby leading to increases in glycaemia. It provides the major counter-regulatory mechanism to insulin in maintaining glucose homeostasis.Hypoglycaemia is the principal stimulus for the secretion of glucagon but may also be used as an antidote in beta-blocker overdose and in anaphylaxis in patients on beta-blockers that fail to respond to adrenaline. Glucagon then causes:GlycogenolysisGluconeogenesisLipolysis in adipose tissueThe secretion of glucagon is also stimulated by:AdrenalineCholecystokininArginineAlanineAcetylcholineThe secretion of glucagon is inhibited by:InsulinSomatostatinIncreased free fatty acidsIncreased urea productionGlycolysis is the metabolic pathway that converts glucose into pyruvate. The free energy released by this process is used to form ATP and NADH. Glycolysis is inhibited by glucagon, and glycolysis and gluconeogenesis are reciprocally regulated so that when one cell pathway is activated, the other is inactive and vice versa.Glucagon has a minor effect of enhancing lipolysis in adipose tissue. Lipolysis is the breakdown of lipids and involves the hydrolysis of triglycerides into glycerol and free fatty acids. It makes fatty acids available for oxidation.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 164
Incorrect
-
The fluid in contact with a tube is dragged by frictional forces to the tube's sidewalls. This creates a velocity gradient in which the fluid flow is greatest in the tube's centre.Which of the following terms most accurately characterizes this flow pattern?
Your Answer: Turbulent flow
Correct Answer: Laminar flow
Explanation:The fluid in contact with a tube is dragged by frictional forces at the tube’s sidewalls. This creates a velocity gradient in which the fluid flow is greatest in the tube’s centre.This is known as laminar flow, and it characterizes the flow in most circulatory and respiratory systems when they are at rest.The velocity of the fluid flow can fluctuate erratically at high velocities, particularly within big arteries and airways, disrupting laminar flow. As a result, resistance increases significantly.This is known as turbulent flow, and symptoms include heart murmurs and asthmatic wheeze.
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This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 165
Correct
-
Which of the following is NOT an effect of gastrin:
Your Answer: Stimulation of insulin release
Explanation:Gastrin acts to:Stimulate acid secretion from parietal cells (both directly and indirectly by stimulating release of histamine from ECL cells)Stimulate pepsinogen secretion from chief cellsIncrease gastric motilityStimulate growth of gastric mucosa
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 166
Correct
-
Noradrenaline exhibits its positive inotropic effect by which of the following mechanisms:
Your Answer: Binds to beta1-receptors and causes increased Ca2+ entry via L-type channels during the action potential
Explanation:Noradrenaline (the sympathetic neurotransmitter) is a positive inotrope; it binds to β1-adrenoceptors on the membrane and causes increased Ca2+entry via L-type channels during the AP and thus increases Ca2+release from the SR. Noradrenaline also increases Ca2+sequestration into the SR and thus more Ca2+is available for the next contraction. Cardiac glycosides (e.g. digoxin) slow the removal of Ca2+from the cell by inhibiting the membrane Na+pump which generates the Na+gradient required for driving the export of Ca2+; consequently the removal of Ca2+from the myocyte is slowed and more Ca2+is available for the next contraction. Acidosis is negatively inotropic, largely because H+competes for Ca2+binding sites.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 167
Correct
-
You come across a 60-year-old woman with a history of chronic pancreatitis. Today she is complaining of epigastric pain. She has blood tests done especially to review her cholecystokinin levels.Which of the following is a cholecystokinin (CCK) releasing site?
Your Answer: I-cells in the upper small intestine
Explanation:The I-cells in the duodenum generate and release cholecystokinin (CCK), a peptide hormone. It has a crucial role in the digestion process as a hormonal regulator.CCK cells are concentrated in the proximal small intestine, and when food is consumed, the hormone is produced into the bloodstream. The presence of partly digested lipids and proteins in the duodenum is one of the most powerful stimulus for CCK synthesis.CCK’s key physiological effects include:Encourages the pancreas to release digesting enzymes into the small intestine.Stimulates gallbladder contraction and sphincter of Oddi relaxation, resulting in bile delivery into the duodenum.Gastric emptying is inhibited, and gastric acid output is reduced.Satiety induction is a process that involves inducing a feeling of fullness.
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This question is part of the following fields:
- Gastrointestinal Physiology
- Physiology
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Question 168
Correct
-
What is the pathophysiology of a phaeochromocytoma:
Your Answer: Catecholamine-secreting tumour
Explanation:Phaeochromocytomas are catecholamine-secreting tumours which occur in about 0.1% of patients with hypertension. In about 90% of cases they arise from the adrenal medulla. The remaining 10%, which arise from extra-adrenal chromaffin tissue, are termed paragangliomas. Common presenting symptoms include one or more of headache, sweating, pallor and palpitations. Less commonly, patients describe anxiety, panic attacks and pyrexia. Hypertension, whether sustained or episodic, is present in at least 90% of patients. Left untreated phaeochromocytoma can occasionally lead to hypertensive crisis, encephalopathy, hyperglycaemia, pulmonary oedema, cardiac arrhythmias, or even death.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 169
Correct
-
A 19-year-old with a longstanding history of asthma presents to the ED with worsening symptoms of cough and wheeze and a peak expiratory flow rate (PEFR) measurement is taken.Which statement concerning PEFR is true?
Your Answer: PEFR is dependent upon the patient's height
Explanation:The maximum flow rate generated during a forceful exhalation, after maximal inspiration is the peak expiratory flow rate (PEFR).PEFR is dependent upon initial lung volume. It is, therefore, dependant on patient’s age, sex and height.PEFR is dependent on voluntary effort and muscular strength of the patient.PEFR is decreased with increasing airway resistance, e.g. in asthma, and it correlates well with the forced expiratory volume in one second (FEV1) value measured in spirometry. This correlation decreases in patients with asthma as airflow decreases.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 170
Incorrect
-
Regarding cardiac excitation-contraction coupling, which of the following statements is CORRECT:
Your Answer: Factors that affect intracellular [Ca 2+ ] and hence cardiac contractility are called chronotropes.
Correct Answer: In relaxation, Ca 2+ is transported out of the cell using energy from a Na + gradient.
Explanation:During the AP plateau, Ca2+enters the cell and activates Ca2+sensitive Ca2+release channels in the sarcoplasmic reticulum allowing stored Ca2+to flood into the cytosol; this is called Ca2+-induced Ca2+release. In relaxation, about 80% of Ca2+is rapidly pumped back into the SR (sequestered) by Ca2+ATPase pumps. The Ca2+that entered the cell during the AP is transported out of the cell primarily by the Na+/Ca2+exchanger in the membrane which pumps one Ca2+ion out in exchange for three Na+ions in, using the Na+electrochemical gradient as an energy source. Increased heart rate increases the force of contraction in a stepwise fashion as intracellular [Ca2+] increases cumulatively over several beats; this is the Treppe effect. Factors that affect intracellular [Ca2+] and hence cardiac contractility are called inotropes.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 171
Correct
-
Bile acids are essential for the digestion and absorption of which of the following:
Your Answer: Lipids and fat-soluble vitamins
Explanation:Bile acids are synthesised from cholesterol by hepatocyte and excreted into bile. Bile acids are essential for lipid digestion and absorption. Of the bile acids excreted into the intestine, about 95% are reabsorbed into the portal circulation by active transport mechanisms in the distal ileum and recycled by the liver. Many of the bile salts are reabsorbed unaltered, some are converted by intestinal bacteria into secondary bile acids (deoxycholic acid and lithocholic acid) and then reabsorbed and a small proportion escapes reabsorption and is excreted in the faeces.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 172
Correct
-
A 57-year-old woman receives vitamin B12 injections following a gastrectomy.Which of the following cell types, if absent, is responsible for her vitamin B12 deficiency?
Your Answer: Parietal cells
Explanation:Intrinsic factor, produced by the parietal cells of the stomach, is essential for the absorption of vitamin B12 from the terminal ileum. After a gastrectomy, the absorption of vitamin B12 is markedly reduced, and a deficiency will occur.
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This question is part of the following fields:
- Gastrointestinal Physiology
- Physiology
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Question 173
Correct
-
By what mechanism does Vibrio cholerae causes diarrhoea?
Your Answer: Increases Cl- secretory channels in crypt cells
Explanation:Cholera is a severe diarrheal illness caused by the Vibrio cholerae bacteria infecting the bowel. Ingesting cholera-infected food or drink is the a way to contract the disease. In the intestinal crypt cells, the toxigenic bacterium Vibrio cholera activates adenylate cyclase and raises cyclic adenosine monophosphate (cAMP). cAMP stimulates the Cl-secretory channels in crypt cells, resulting in the secretion of chloride with sodium ions and water. The toxin it produces causes the body to secrete massive amounts of water, resulting in diarrhoea and significant fluid and electrolyte loss.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 174
Correct
-
Which of the following cell types in the stomach secretes histamine?
Your Answer: Enterochromaffin-like cells
Explanation:The parietal cells operate in close association with another type of cell called enterochromaffin-like cells (ECL cells), the primary function of which is to secrete histamine. The ECL cells lie in the deep recesses of the oxyntic glands and therefore release histamine indirect contact with the parietal cells of the glands.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 175
Correct
-
Which of the following factors does NOT decrease glucagon secretion:
Your Answer: Catecholamines
Explanation:Factors that increase glucagon secretion:↓ Blood glucose↑ Amino acidsCholecystokininCatecholaminesAcetylcholineFactors that decrease glucagon secretion:↑ Blood glucoseInsulinSomatostatinFatty acids, ketoacids
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 176
Correct
-
An elderly patient presents to ED following a fall after feeling light headed when standing up. You are reviewing his medication and note that he is taking a high dose of furosemide. Loop diuretics act primarily at which of the following sites in the nephron:
Your Answer: Thick ascending limb
Explanation:Loop diuretics inhibit the Na+/K+/2Cl- symporter on the luminal membrane in the thick ascending limb of the loop of Henle, thus preventing reabsorption of NaCl and water. These agents reduce reabsorption of Cl- and Na+ and increase Ca2+ excretion and loss of K+ and Mg2+.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 177
Incorrect
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Question 178
Incorrect
-
Regarding carbon dioxide transport in the blood, which of the following statements is CORRECT:
Your Answer: Carbon dioxide is formed from the dissociation of bicarbonate ions.
Correct Answer: Deoxygenated haemoglobin acts as a buffer for H+ ions.
Explanation:CO2generated in the tissues and water combine to form carbonic acid which readily dissociates to form HCO3-and H+. The first part of this reaction is very slow in plasma, but is accelerated dramatically by the enzyme carbonic anhydrase present in red blood cells. Bicarbonate is therefore formed preferentially in red cells, from which it freely diffuses down its concentration gradient into plasma where it is transported to the lungs. The red cell membrane is impermeable to H+ions which remain in the cell. To maintain electroneutrality, Cl-ions diffuse into the cell to replace HCO3-, an effect known as the chloride shift. Deoxygenated haemoglobin acts as a buffer for H+, allowing the reaction to continue.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 179
Correct
-
For a tachyarrhythmia caused by hypovolaemic shock, which of the following is the first-line treatment:
Your Answer: Synchronised DC shock
Explanation:If there are any adverse symptoms, immediate cardioversion with synchronized DC shock is recommended. If cardioversion fails to stop the arrhythmia and the symptoms persist, amiodarone 300 mg IV over 10–20 minutes should be administered before attempting another cardioversion. The loading dosage of amiodarone is followed by a 24-hour infusion of 900 mg administered into a large vein.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 180
Correct
-
The QRS duration of a broad-complex tachyarrhythmia is:
Your Answer: Greater than or equal to 0.12 s
Explanation:It’s a broad-complex tachycardia if the QRS duration is 0.12 seconds or more. It’s a narrow-complex tachycardia if the QRS complex is shorter than 0.12 seconds. The QRS duration should be examined if the patient with tachyarrhythmia is stable.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 181
Correct
-
Which of the following statements about vitamin B12 absorption is TRUE:
Your Answer: On ingestion, vitamin B12 is bound to R protein which protects it from digestion in the stomach.
Explanation:The substance intrinsic factor,essential for absorption of vitamin B12 in the ileum, issecreted by the parietal cells along with the secretion ofhydrochloric acid. When the acid-producing parietalcells of the stomach are destroyed, which frequentlyoccurs in chronic gastritis, the person develops not onlyachlorhydria (lack of stomach acid secretion) but oftenalso pernicious anaemia because of failure of maturationof the red blood cells in the absence of vitamin B12 stimulation of the bone marrow.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 182
Correct
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Which of the following is typically a cause of a normal anion gap metabolic acidosis:
Your Answer: Diarrhoea
Explanation:FUSEDCARS can be used to remember some of the causes of a normal anion gap acidosis:Fistula (pancreaticoduodenal)Ureteroenteric conduitSaline administrationEndocrine (hyperparathyroidism)DiarrhoeaCarbonic anhydrase inhibitors (e.g. acetazolamide)Ammonium chlorideRenal tubular acidosisSpironolactone
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This question is part of the following fields:
- Physiology
- Renal
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Question 183
Incorrect
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Which law describes the rate of diffusion in a solution?
Your Answer: Darcy’s law
Correct Answer: Fick’s law
Explanation:Fick’s law describes the rate of diffusion in a solution. Fick’s law states that:Jx = -D A (ΔC / Δx)Where:Jx = The amount of substance transferred per unit timeD = Diffusion coefficient of that particular substanceA = Surface area over which diffusion occursΔC = Concentration difference across the membraneΔx = Distance over which diffusion occursThe negative sign reflects movement down the concentration gradient
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This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 184
Incorrect
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Regarding alteplase, which of the following statements is INCORRECT:
Your Answer: Alteplase has selectivity for activation of fibrin-bound plasminogen.
Correct Answer: Alteplase is commonly associated with hypotensive effects.
Explanation:Alteplase is a recombinant tissue-type plasminogen activator (tPA), a naturally occurring fibrin-specific enzyme that has selectivity for activation of fibrin-bound plasminogen. It has a short half-life of 3 – 4 minutes and must be given by continuous intravenous infusion but is not associated with antigenic or hypotensive effects, and can be used in patients when recent streptococcal infections or recent use of streptokinase contraindicates the use of streptokinase.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 185
Incorrect
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Which of the following statements regarding the pituitary gland is CORRECT:
Your Answer: Hypothalamic hormones are transported to the posterior pituitary by hypophyseal portal vessels.
Correct Answer: Cortisol inhibits release of adrenocorticotropic hormone (ACTH) from the anterior pituitary.
Explanation:Anterior pituitary hormones are released under the control of hypothalamic releasing or inhibiting hormones originating from small neurons with their cell bodies in the hypothalamus and released into the blood at the median eminence. These hypothalamic hormones are transported directly to the anterior pituitary via hypophyseal portal vessels. The anterior pituitary hormones (and the hormones released by their target organs) inhibit further release of hypothalamic and anterior pituitary hormones by negative feedback mechanisms e.g. cortisol inhibits the release of ACTH. Prolactin release from the anterior pituitary is inhibited by dopamine.The posterior pituitary is really a direct extension of the hypothalamus. Oxytocin and ADH are manufactured in the cell bodies of large neurons in the hypothalamus and are transported down the axons of these cells to their terminals on capillaries originating from the inferior hypophyseal artery within the posterior pituitary gland. ADH release is controlled by negative feedback mechanisms based on plasma osmolality and blood volume, oxytocin however is involved in positive feedback mechanisms.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 186
Incorrect
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All of the following statements are incorrect about insulin except:
Your Answer: The effects of insulin are mediated by a G-protein coupled receptor.
Correct Answer: Proinsulin is cleaved into insulin and C peptide.
Explanation:Proinsulin is synthesised as a single-chain peptide. A connecting peptide (C peptide) within storage granules is removed by proteases to yield insulin. Insulin:1. is a polypeptide hormone consisting of two short chains (A and B) linked by disulphide bonds. 2. is produced by beta cells, located centrally within the islets of Langerhans, in the endocrine tissues of the pancreas. 3. release is stimulated initially during eating by the parasympathetic nervous system and gut hormones such as secretin. However, most output is driven by the rise in plasma glucose concentration that occurs after a meal. 4. effects are mediated by the receptor tyrosine kinase.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 187
Correct
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A 58-year-old woman presents with symptoms of increase in weight, proximal muscular weakening and withering, easy bruising, and acne. You notice that she has a full, plethoric aspect to her face, as well as significant supraclavicular fat pads, when you examine her. She has previously been diagnosed with Cushing's syndrome.Which of the following biochemical profiles best supports this diagnosis?
Your Answer: Hypokalaemic metabolic alkalosis
Explanation:Cushing’s syndrome is a group of symptoms and signs brought on by long-term exposure to high amounts of endogenous or exogenous glucocorticoids. Cushing’s syndrome affects about 10-15 persons per million, and it is more common in those who have had a history of obesity, hypertension, or diabetes.A typical biochemical profile can help establish a diagnosis of Cushing’s syndrome. The following are the primary characteristics:HypokalaemiaAlkalosis metabolique
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 188
Correct
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Continuous capillaries are typically found where in the body:
Your Answer: Blood-brain barrier
Explanation:Continuous capillaries, found in the skin, lungs, muscles and CNS, are the most selective with low permeability, as junctions between the endothelial cells are very tight, restricting the flow of molecules with MW > 10,000.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 189
Correct
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Regarding the glomerular filtration barrier, which of the following statements is CORRECT:
Your Answer: The main factor determining whether a substance is filtered or not is molecular weight.
Explanation:Molecular weight is the main factor in determining whether a substance is filtered or not – molecules < 7 kDa in molecular weight are filtered freely e.g. glucose, amino acids, urea, ions but larger molecules are increasingly restricted up to 70 kDa, above which filtration is insignificant. Negatively charged molecules are further restricted, as they are repelled by negative charges, particularly in the basement membrane. Albumin has a molecular weight of 69 kDa and is negatively charged, thus only very small amounts are filtered (and all of the filtered albumin is reabsorbed in the proximal tubule), whereas small molecules such as ions, glucose, amino acids and urea pass the filter without hindrance. This means that ultrafiltrate is virtually protein free, but otherwise has an identical composition of that of plasma. The epithelial lining of the Bowman's capsule consists of a single layer of cells called podocytes. The glomerular capillary endothelium is perforated by pores (fenestrations) which allow plasma components with a molecular weight of < 70 kDa to pass freely.
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This question is part of the following fields:
- Physiology
- Renal
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Question 190
Correct
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In the foetus at 4 months gestation, where does haematopoiesis mainly occur?
Your Answer: Liver and spleen
Explanation:The first place that haematopoiesis occurs in the foetus is in the yolk sac. Later on, it occurs in the liver and spleen, which are the major hematopoietic organs from about 6 weeks until 6 – 7 months gestation. At this point, the bone marrow becomes the most important site. Haemopoiesis is restricted to the bone marrow in normal childhood and adult life.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 191
Incorrect
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The correct statement regarding the parasympathetic nervous system is which of the following?
Your Answer: Parasympathetic ganglia lie in chains beside the vertebral column.
Correct Answer: Parasympathetic preganglionic neurones run in cranial nerves III, VII, IX and X.
Explanation:The electron transfer system is responsible for most of the energy produced during respiration. The is a system of hydrogen carriers located in the inner mitochondrial membrane. Hydrogen is transferred to the electron transfer system via the NADH2 molecules produced during glycolysis and the Krebs cycle. As a result, a H+ion gradient is generated across the inner membrane which drives ATP synthase. The final hydrogen acceptor is oxygen and the H+ions and O2 combine to form water.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 192
Correct
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Regarding cardiac excitation-contraction coupling, which of the following statements is CORRECT:
Your Answer: The Treppe effect refers to an increase in contractility secondary to an increase in heart rate.
Explanation:Although Ca2+entry during the action potential (AP) is essential for contraction, it only accounts for about 25% of the rise in intracellular Ca2+. The rest is released from Ca2+stores in the sarcoplasmic reticulum (SR). In relaxation, about 80% of Ca2+is rapidly pumped back into the SR (sequestered) by Ca2+ATPase pumps. The Ca2+that entered the cell during the AP is transported out of the cell primarily by the Na+/Ca2+exchanger in the membrane. When more action potentials occur per unit time, more Ca2+enters the cell during the AP plateau, more Ca2+is stored in the SR, more Ca2+is released from the SR and thus more Ca2+is left inside the cell and greater tension is produced during contraction. Increased heart rate increases the force of contraction in a stepwise fashion as intracellular [Ca2+] increases cumulatively over several beats; this is the Treppe effect. Cardiac glycosides such as digoxin have a positive inotropic effect.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 193
Incorrect
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ACE inhibitors are indicated for all of the following EXCEPT for:
Your Answer: Heart failure
Correct Answer: Angina
Explanation:ACE inhibitors have many uses and are generally well tolerated. They are indicated for:Heart failureHypertensionDiabetic nephropathySecondary prevention of cardiovascular events
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 194
Correct
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A patients had a left Colles' fracture, which you were able to repair. It was their second fragility fracture this year, and you'd like to provide them some tips on how to keep their bones healthy.What percentage of the calcium in the body is kept in the bones? Only ONE response is acceptable.
Your Answer: 99%
Explanation:Calcium is stored in bones for nearly all of the body’s calcium, but it is also found in some cells (most notably muscle cells) and the blood. The average adult diet comprises roughly 25 mmol of calcium per day, of which the body absorbs only about 5 mmol.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 195
Incorrect
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You've been asked to visit a 20-year-old patient who has been complaining of stomach pain, diarrhoea, and bloating. The GP recently saw the patient and is now looking into numerous possible reasons for stomach hypermotility.Which of the following factors contributes to increased stomach motility?
Your Answer: Ghrelin
Correct Answer: Gastrin
Explanation:Gastrin is a peptide hormone that aids in gastric motility by stimulating the generation of gastric acid by the parietal cells of the stomach. G-cells in the stomach’s pyloric antrum, the duodenum, and the pancreas release it.The following stimuli cause the release of gastrin:Stimulation of the vagus nerveHypercalcaemiastomach bloatingProteins that have been partially digested, particularly amino acids.The presence of acid and somatostatin inhibits the release of gastrin.Gastrin’s main actions are as follows:Gastric parietal cells are stimulated to release hydrochloric acid.ECL cells are stimulated to produce histamine.Gastric parietal cell maturation and fundal growth stimulationCauses the secretion of pepsinogen by the gastric chief cells.Improves antral muscle mobility stimulates gastric contractionsIncreases gastric emptying rate and stimulates pancreatic secretionGallbladder emptying is induced.
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This question is part of the following fields:
- Gastrointestinal Physiology
- Physiology
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Question 196
Correct
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Molecules with a molecular weight of less than which of the following are filtered freely at the glomerular filtration barrier:
Your Answer: 7000 Da
Explanation:Molecular weight is the main factor in determining whether a substance is filtered or not – molecules < 7 kDa in molecular weight are filtered freely e.g. glucose, amino acids, urea, ions but larger molecules are increasingly restricted up to 70 kDa, above which filtration is insignificant. Negatively charged molecules are further restricted, as they are repelled by negative charges, particularly in the basement membrane. Albumin has a molecular weight of 69 kDa and is negatively charged, thus only very small amounts are filtered (and all of the filtered albumin is reabsorbed in the proximal tubule), whereas small molecules such as ions, glucose, amino acids and urea pass the filter without hindrance. This means that ultrafiltrate is virtually protein free, but otherwise has an identical composition of that of plasma. The epithelial lining of the Bowman's capsule consists of a single layer of cells called podocytes. The glomerular capillary endothelium is perforated by pores (fenestrations) which allow plasma components with a molecular weight of < 70 kDa to pass freely.
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This question is part of the following fields:
- Physiology
- Renal
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Question 197
Incorrect
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1-alpha-hydroxylase is a cytochrome p450 enzyme that is involved in the production of vitamin D's hormonally active metabolite.Which of the following promotes the activity of 1-alpha-hydroxylase?
Your Answer: 25-hydroxylase
Correct Answer: Parathyroid hormone
Explanation:1-alpha-hydroxylase converts 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol in the kidney.The key regulatory point in the formation of 1,25-dihydroxycholecalciferol is 1-alpha-hydroxylase, which is promoted by parathyroid hormone or hypophosphatemia.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 198
Correct
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Dexamethasone would be most useful for which of the following conditions:
Your Answer: Raised intracranial pressure secondary to malignancy
Explanation:Dexamethasone has a very high glucocorticoid activity in conjunction with insignificant mineralocorticoid activity. This makes it particularly suitable for high-dose therapy in conditions where fluid retention would be a disadvantage such as in the management of raised intracranial pressure or cerebral oedema secondary to malignancy. Dexamethasone also has a long duration of action and this, coupled with its lack of mineralocorticoid action makes it particularly suitable for suppression of corticotropin secretion in congenital adrenal hyperplasia. In most individuals a single dose of dexamethasone at night, is sufficient to inhibit corticotropin secretion for 24 hours. This is the basis of the ‘overnight dexamethasone suppression test’ for diagnosing Cushing’s syndrome.
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This question is part of the following fields:
- Endocrine
- Pharmacology
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Question 199
Incorrect
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When treating diabetic ketoacidosis (DKA), which of the following should be given if the systolic blood pressure is initially less than 90 mmHg:
Your Answer: 1 L sodium chloride 0.9% intravenous infusion over 10 - 15 minutes
Correct Answer: 500 mL sodium chloride 0.9% intravenous infusion over 10 - 15 minutes
Explanation:If SBP is less than 90 mmHg , 500 mL sodium chloride 0.9 percent should be administered intravenously over 10–15 minutes, and repeated if SBP remains less than 90 mmHg. When SBP is greater than 90 mmHg, sodium chloride infusion must be maintained at a rate that replaces the deficit.
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This question is part of the following fields:
- Endocrine
- Pharmacology
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Question 200
Correct
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Antidiuretic hormone (ADH) levels are found to be increased in a young lady with unexplained hyponatraemia.Which of the following is a result of the release of ADH?
Your Answer: Small volumes of concentrated urine
Explanation:ADH, or antidiuretic hormone, is a hormone that regulates water and electrolyte balance. It is released in response to a variety of events, the most important of which are higher plasma osmolality or lower blood pressure. ADH increases plasma volume and blood pressure via acting on the kidneys and peripheral vasculature.ADH causes extensive vasoconstriction by acting on peripheral V1 Receptors.ADH binds to B2 Receptors in the terminal distal convoluted tubule and collecting duct of the kidney, increasing transcription and aquaporin insertion in the cells that line the lumen. Aquaporins are water channels that allow water to pass through the tubule and into the interstitial fluid via osmosis, lowering urine losses.The permeability of the distal collecting duct (the section within the inner medulla) to urea is likewise increased by ADH. More urea travels out of the tubule and into the peritubular fluid, contributing to the counter current multiplier, which improves the Loop of Henle’s concentrating power.Overall, there is enhanced urea and water reabsorption in the presence of ADH, resulting in modest amounts of concentrated urine. There is minimal urea and water reabsorption in the absence of ADH, resulting in huge amounts of dilute urine.
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This question is part of the following fields:
- Physiology
- Renal Physiology
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SESSION STATS - PERFORMANCE PER SPECIALTY
