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Question 1
Incorrect
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Vitamin D is a group of secosteroids that play a role in calcium and phosphate control. Vitamin D's hormonally active metabolite is 1,25-dihydroxycholecalciferol.Which enzyme hydroxylates 25-hydroxycholecalciferol to form 1,25-dihydroxycholecalciferol?
Your Answer: 25-hydroxylase
Correct Answer: 1-alpha-hydroxylase
Explanation:The hormone-active metabolite of vitamin D is 1,25-dihydroxycholecalciferol (commonly known as calcitriol). Its activities raise calcium and phosphate levels in the bloodstream.In the presence of UVB light, 7-dehydrocholesterol is converted to cholecalciferol in the epidermal layer of the skin, resulting in 1,25-dihydroxycholecalciferol.Cholecalciferol is then converted to 25-hydroxycholecalciferol in the endoplasmic reticulum of liver hepatocytes by 25-hydroxylase (calcifediol).Finally, 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 induced by parathyroid hormone or hypophosphatemia.The following are the primary effects of 1,25-dihydroxycholecalciferol:Calcium and phosphate absorption in the small intestine is increased.Calcium reabsorption in the kidneys is increased.Increases phosphate reabsorption in the kidneys.Increases the action of osteoclastic bacteria (increasing calcium and phosphate resorption from bone)Inhibits the action of 1-alpha-hydroxylase in the kidneys (negative feedback)
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 2
Correct
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All of the following are physiological effects of thyroid hormones except:
Your Answer: Increased glycogenesis
Explanation:Thyroid hormones have multiple physiological effects on the body. These include:1. Heat production (thermogenesis)2. Increased basal metabolic rate3. Metabolic effects: (a) Increase in protein turnover (both synthesis and degradation are increased, although overall effect is catabolic)(b) Increase in lipolysis(c)Increase in glycogenolysis and gluconeogenesis4. Enhanced catecholamine effect – Increase in heart rate, stroke volume and thus cardiac output5. Important role in growth and development
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 3
Correct
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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 4
Incorrect
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Following a decrease in extracellular volume, which of the following is a reaction to enhanced sympathetic innervation of the kidney:
Your Answer: Decreased Na + reabsorption
Correct Answer: Release of renin
Explanation:The RAS pathway begins with renin cleaving its substrate, angiotensinogen (AGT), to produce the inactive peptide, angiotensin I, which is then converted to angiotensin II by endothelial angiotensin-converting enzyme (ACE). ACE activation of angiotensin II occurs most extensively in the lung. Angiotensin II mediates vasoconstriction as well as aldosterone release from the adrenal gland, resulting in sodium retention and increased blood pressure.
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This question is part of the following fields:
- Physiology
- Renal
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Question 5
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 6
Incorrect
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Regarding the management of diabetic ketoacidosis (DKA), insulin should initially be given:
Your Answer: At a concentration of 0.1 units/mL at a fixed rate of 1 units/kg/hour
Correct Answer: At a concentration of 1 unit/mL at a fixed rate of 0.1 units/kg/hour
Explanation:An intravenous insulin infusion should be started at a concentration of 1 unit/mL, at a fixed rate of 0.1 units/kg/hour. Established subcutaneous long-acting insulin therapy should be continued concomitantly. Blood ketone and blood glucose concentrations should be checked hourly and the insulin infusion rate adjusted accordingly. Blood ketone concentration should fall by at least 0.5 mmol/litre/hour and blood glucose concentration should fall by at least 3 mmol/litre/hour.
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This question is part of the following fields:
- Endocrine
- Pharmacology
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Question 7
Correct
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A pheochromocytoma is diagnosed in a 38-year-old female who has had episodes of acute sweating, palpitations, and paroxysmal hypertension.Which of the following is the MOST SUITABLE INITIAL TREATMENT?
Your Answer: Alpha-blocker
Explanation:A phaeochromocytoma is a rare functional tumour that develops in the adrenal medulla from chromaffin cells. Extra-adrenal paragangliomas (extra-adrenal pheochromocytomas) are tumours that arise in the sympathetic nervous system’s ganglia and are closely connected to extra-adrenal paragangliomas (extra-adrenal pheochromocytomas). Catecholamines are secreted by these tumours, which generate a variety of symptoms and indications associated with sympathetic nervous system hyperactivity.Hypertension is the most prevalent presenting symptom, which can be continuous or intermittent.Symptoms are usually intermittent, occurring anywhere from many times a day to occasionally. The symptoms of the condition tend to grow more severe and frequent as the disease progresses.The ultimate therapy of choice is surgical resection, and if full resection is done without metastases, hypertension is typically cured.Preoperative medical treatment is critical because it lowers the risk of hypertensive crises during surgery. This is commonly accomplished by combining non-competitive alpha-blockers (such as phenoxybenzamine) with beta-blockers. To allow for blood volume expansion, alpha-blockade should be started at least 7-10 days before surgery. Beta-blockade, which helps to regulate tachycardia and some arrhythmias, can be started after this is accomplished. Hypertensive crises can be triggered if beta-blockade is started too soon.There should also be genetic counselling, as well as a search for and management of any linked illnesses.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 8
Correct
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Beta cells of the endocrine pancreas produce which of the following hormones:
Your Answer: Insulin
Explanation:Insulin is produced by beta cells, located centrally within the islets of Langerhans, in the endocrine tissues of the pancreas. Insulin is a polypeptide hormone consisting of two short chains (A and B) linked by disulphide bonds. Proinsulin is synthesised as a single-chain peptide. Within storage granules, a connecting peptide (C peptide) is removed by proteases to yield insulin. Insulin release is stimulated initially during eating by the parasympathetic nervous system and gut hormones such as secretin, but most output is driven by the rise in plasma glucose concentration that occurs after a meal. The effects of insulin 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 9
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 10
Correct
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Regarding calcium channel blockers, which of the following statements is CORRECT:
Your Answer: Calcium channel blockers inhibit L-type voltage-sensitive calcium channels in arterial smooth muscle causing vasodilation.
Explanation:Calcium channel blockers inhibit L-type voltage-sensitive calcium channels in arterial smooth muscle, causing relaxation and vasodilation (reduction in peripheral vascular resistance). They also block calcium channels within the myocardium and conducting tissues of the heart which produces a negative inotropic effect by reducing calcium influx during the plateau phase of the action potential. They have a variety of uses, including:HypertensionAnginaAtrial fibrillationMigraineCalcium channel blockers have been found to be moderately useful in the prevention of migraines. The best evidence is for this is with verapamil. This may be due to the prevention of the arteriolar constriction that is associated with migraine. They are commonly used for this elsewhere in the world but are not currently licensed for this use in the UK.The following are common side effects of all calcium-channel blockers:Abdominal painDizzinessDrowsinessFlushingHeadacheNausea and vomitingPalpitationsPeripheral oedemaSkin reactionsTachycardiaVerapamil is highly negatively inotropic and reduces cardiac output, slows the heart rate and may impair atrioventricular conduction. It may precipitate heart failure, exacerbate conduction disorders, and cause hypotension at high doses and should not be used with beta-blockers. Nifedipine has less myocardial effects than verapamil and has no antiarrhythmic properties but has more influence on the vessels. Nimodipine is used solely for the prevention and treatment of vascular spasm following aneurysmal subarachnoid haemorrhage.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 11
Correct
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You review an 83-year-old woman who has stage 5 chronic kidney disease. She has a number of electrolyte problems.Which ONE of the following decreases the renal reabsorption of phosphate?
Your Answer: Parathyroid hormone
Explanation:Parathyroid hormone (PTH) is a polypeptide containing 84 amino acids. It is the principal controller of free calcium in the body.The main actions of parathyroid hormone are:Increases plasma calcium concentrationDecreases plasma phosphate concentrationIncreases osteoclastic activity (increasing calcium and phosphate resorption from bone)Increases renal tubular reabsorption of calciumDecreases renal phosphate reabsorptionIncreases renal conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol (via stimulation of 1-alpha hydroxylase)Increases calcium and phosphate absorption in the small intestine (indirectly via increased 1,25-dihydroxycholecalciferol)
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 12
Correct
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Which of the following describes the pulse pressure:
Your Answer: Systolic - diastolic pressure
Explanation:During systole, the pressure in the left ventricle increases and blood is ejected into the aorta. The rise in pressure stretches the elastic walls of the aorta and large arteries and drives blood flow. Systolic pressure is the maximum arterial pressure during systole. During diastole, arterial blood flow is partly maintained by elastic recoil of the walls of large arteries. The minimum pressure reached before the next systole is the diastolic pressure. The difference between the systolic and diastolic pressure is the pulse pressure.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 13
Incorrect
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A 50-year-old man, known hypertensive on amlodipine has been visiting his GP with symptoms of headache, tiredness, and muscle weakness. His blood test today shows a low potassium level of 2.8 mmol/L, and a slightly raised sodium level at 147 mmol/L.What is the MOST LIKELY diagnosis?
Your Answer: Addison’s disease
Correct Answer: Conn’s syndrome
Explanation:When there are excessive levels of aldosterone independent of the renin-angiotensin aldosterone axis, primary hyperaldosteronism occurs. Secondary hyperaldosteronism occurs due to high renin levels.Causes of primary hyperaldosteronism include:Conn’s syndromeAdrenal hyperplasiaAdrenal cancerFamilial aldosteronismCauses of secondary hyperaldosteronism include:Renal vasoconstrictionOedematous disordersDrugs – diureticsObstructive renal artery diseaseAlthough patients are usually asymptomatic, when clinical features are present, classically hyperaldosteronism presents with:HypokalaemiaSodium levels can be normal or slightly raisedHypertensionMetabolic alkalosisLess common, clinical features are:LethargyHeadachesIntermittent paraesthesiaPolyuria and polydipsiaMuscle weakness (from persistent hypokalaemia)Tetany and paralysis (rare)
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 14
Incorrect
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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: Bendroflumethiazine
Correct 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 15
Incorrect
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Mannitol is primarily indicated for which of the following:
Your Answer: Hypertension
Correct 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 16
Incorrect
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Action potentials are transmitted from myocyte to myocyte via which of the following:
Your Answer: Tight junctions
Correct Answer: Gap junctions
Explanation:Action potentials are transmitted to adjacent myocytes via gap junctions.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 17
Correct
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During swallowing, which of the following structures primarily closes the tracheal opening:
Your Answer: Epiglottis
Explanation:The vocal cords of the larynx are stronglyapproximated, and the larynx is pulled upwardand anteriorly by the neck muscles. These actions,combined with the presence of ligaments thatprevent upward movement of the epiglottis, causethe epiglottis to swing back over the openingof the larynx. All these effects acting togetherprevent the passage of food into the nose andtrachea. Most essential is the tight approximationof the vocal cords, but the epiglottis helps toprevent food from ever getting as far as the vocalcords. Destruction of the vocal cords or of themuscles that approximate them can causestrangulation.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 18
Correct
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Pre-oxygenation is done prior to intubation to extend the ‘safe apnoea time’.Which lung volume or capacity is the most important store of oxygen in the body?
Your Answer: Functional residual capacity
Explanation:The administration of oxygen to a patient before intubation is called pre-oxygenation and it helps extend the ‘safe apnoea time’. The Functional residual capacity (FRC) is the volume of gas that remains in the lungs after normal tidal expiration. It is the most important store of oxygen in the body. The aim of pre-oxygenation is to replace the nitrogen in the FRC with oxygen. Apnoea can be tolerated for longer periods before critical hypoxia develops if the FRC is large. Patients with reduced FRC reach critical hypoxia more rapidly.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 19
Incorrect
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Antispasmodic drugs are primarily indicated in which of the following conditions:
Your Answer: Gastroenteritis
Correct Answer: Irritable bowel syndrome
Explanation:Antispasmodics, such as antimuscarinics, may be used in the management of irritable bowel syndrome. Other antispasmodics used include direct-acting smooth muscle relaxants such as mebeverine, alverine, and peppermint oil. Antispasmodics are contraindicated in bowel obstruction and severe inflammatory bowel disease. Antispasmodics are occasionally of value in treating abdominal cramp associated with diarrhoea but they should not be used for primary treatment. Antispasmodics should be avoided in young children with gastroenteritis because they are rarely effective and have troublesome side effects. Antimuscarinics are contraindicated in urinary retention.
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This question is part of the following fields:
- Gastrointestinal
- Pharmacology
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Question 20
Incorrect
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A 39-year-old woman is feeling unwell one week after a parathyroid surgery.Which of the following stimulates release of parathyroid hormone (PTH)?
Your Answer: Increased plasma calcium concentration
Correct Answer: Increased plasma phosphate concentration
Explanation:PTH is synthesised and released from the chief cells of the four parathyroid glands located behind the thyroid gland.It is a polypeptide containing 84 amino acids and it controls free calcium in the body.The following stimuli causes release of PTH:Increased plasma phosphate concentrationDecreased plasma calcium concentrationPTH release is inhibited by:Normal or increased plasma calcium concentrationHypomagnesaemiaThe main actions of PTH are:Increases plasma calcium concentrationDecreases plasma phosphate concentrationIncreases osteoclastic activity (increasing calcium and phosphate resorption from bone)Increases renal tubular reabsorption of calciumDecreases renal phosphate reabsorptionIncreases renal conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol (via stimulation of 1-alpha hydroxylase)Increases calcium and phosphate absorption in the small intestine (indirectly via increased 1,25-dihydroxycholecalciferol)
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 21
Incorrect
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Gastrin release from antral G-cells is stimulated by all but which one of the following:
Your Answer: Raised gastric pH
Correct Answer: Secretin
Explanation:Gastrin secretion is stimulated by: The presence of small peptides and amino acids in chymeGastric distensionVagal stimulation directly via acetylcholine and indirectly via gastrin-releasing peptide (GRP)Raised gastric pH
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 22
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 23
Incorrect
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What is the primary mode of action of Enoxaparin?
Your Answer: Directly inhibits thrombin
Correct 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 24
Incorrect
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Angiotensin II acts to cause all but which one of the following effects:
Your Answer: Directly increase Na + reabsorption from the proximal tubule
Correct 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 25
Incorrect
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Which one of these equations best defines lung compliance?
Your Answer: Change in volume / positive end-expiratory pressure
Correct Answer: Change in volume / change in pressure
Explanation:Lung compliance is defined as change in volume per unit change in distending pressure. Lung compliance is calculated using the equation:Lung compliance = ΔV / ΔPWhere:ΔV is the change in volumeΔP is the change in pleural pressure.Static compliance is lung compliance in periods without gas flow, and is calculated using the equation:Static compliance = VT / Pplat − PEEPWhere:VT = tidal volumePplat = plateau pressurePEEP = positive end-expiratory pressure
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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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Angiotensin II is part of the RAAS system. One of its effects is the constriction of efferent arterioles. Which of the following best describes the effect of angiotensin II- mediated constriction of efferent arterioles?
Your Answer: Decreased renal plasma flow, increased filtration fraction, decreased GFR
Correct Answer: Decreased renal plasma flow, increased filtration fraction, increased GFR
Explanation:The Renin-Angiotensin-Aldosterone System (RAAS) is a hormone system composed of renin, angiotensin, and aldosterone. Those hormones are essential for the regulation of blood pressure and fluid balance. Cases of hypotension, sympathetic stimulation, or hyponatremia can activate the Renin-angiotensin-aldosterone system (RAAS). The following process will then increase the blood volume and blood pressure as a response. When renin is released it will convert the circulating angiotensinogen to angiotensin I. The ACE or angiotensin-converting enzyme will then catalyst its conversion to angiotensin II, which is a potent vasoconstrictor. Angiotensin II can constrict the vascular smooth muscles and the efferent arteriole of the glomerulus. The efferent arteriole is a blood vessel that delivers blood away from the capillaries of the kidney. The angiotensin II-mediated constriction of efferent arterioles increases GFR, reduces renal blood flow and peritubular capillary hydrostatic pressure, and increases peritubular colloid osmotic pressure, as a response to its action of increasing the filtration fraction.
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This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 27
Incorrect
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A 58-year-old patient presents with sputum production and worsening exertional breathlessness. A spirometry is done and his results leads to a diagnosis of obstructive lung disease with mild airflow obstruction.What FEV1 value would correspond with mild airflow obstruction according to the NICE guidelines?
Your Answer: FEV 1 50-79%
Correct Answer: FEV 1 >80%
Explanation:Airflow obstruction according to the latest NICE guidelines, is defined as: Mild airflow obstruction = an FEV 1 of >80% in the presence of symptoms Moderate airflow obstruction = FEV 1 of 50-79% Severe airflow obstruction = FEV 1 of 30-49% Very severe airflow obstruction = FEV1<30%.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 28
Correct
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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 29
Incorrect
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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: Malignancy
Correct 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 30
Incorrect
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Regarding carbon dioxide transport in the blood, which of the following statements is CORRECT:
Your Answer: Carbonic anhydrase is absent in red blood cells.
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 31
Incorrect
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A 30-year-old woman with type 1 diabetes mellitus is brought in drowsy and confused. Her BM is 2.2 mmol/l and a dose of IM glucagon is administered.What is the principal stimulus for the secretion of glucagon?
Your Answer: Somatostatin
Correct Answer: Hypoglycaemia
Explanation:Glucagon, a peptide hormone, is produced and secreted by alpha cells of the islets of Langerhans, located in the endocrine portion of the pancreas. Its main physiological role is stimulation of hepatic glucose output leading to increase in blood glucose. It is the major counter-regulatory hormone to insulin in maintaining glucose homeostasis.The principal stimulus for the secretion of glucagon is hypoglycaemia. Hypoglycaemia then stimulates:GlycogenolysisGluconeogenesisLipolysis in adipose tissue leading to increased glycaemia.Secretion of glucagon is also stimulated by arginine, alanine, adrenaline, acetylcholine and cholecystokininSecretion of glucagon is inhibited by:InsulinSomatostatinIncreased free fatty acidsIncreased urea production
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 32
Incorrect
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The functional residual capacity (FRC) will be decreased in which of the following:
Your Answer: Aging
Correct Answer: Pulmonary fibrosis
Explanation:Factors decreasing FRC:Restrictive ventilatory defects e.g. pulmonary fibrosisPosture – lying supineIncreased intra-abdominal pressure (e.g. obesity, pregnancy, ascites)Reduced muscle tone of diaphragm e.g. muscle relaxants in anaesthesia, neuromuscular disease
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 33
Incorrect
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Noradrenaline exhibits its positive inotropic effect by which of the following mechanisms:
Your Answer: Slows the removal of Ca2+ from the cell by inhibiting the membrane Na+/Ca2+ exchanger
Correct 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 34
Incorrect
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Regarding postural hypotension, which of the following statements is INCORRECT:
Your Answer: Postural hypotension is usually corrected quickly by the baroreceptor reflex.
Correct Answer: Postural hypotension usually causes a reflex bradycardia.
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 35
Incorrect
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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: Thin ascending limb
Correct 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 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 is caused by an alpha-1 antitrypsin deficiency?
Your 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 38
Incorrect
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ACE inhibitors are indicated for all of the following EXCEPT for:
Your Answer: Diabetic nephropathy
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 39
Incorrect
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Arterial baroreceptors are located primarily in which of the following:
Your Answer: Right atrium
Correct Answer: Carotid sinus and aortic arch
Explanation:Arterial baroreceptors are located in the carotid sinus and aortic arch, and detect the mean arterial pressure (MAP). A decrease in MAP (such as in postural hypotension, or haemorrhage) reduces arterial stretch and decreases baroreceptor activity, resulting in decreased firing in afferent nerves travelling via the glossopharyngeal nerve (carotid sinus) and vagus nerve (aortic arch) to the medulla where the activity of the autonomic nervous system is coordinated. Sympathetic nerve activity consequently increases, causing an increase in heart rate and cardiac contractility, peripheral vasoconstriction with an increase in TPR, and venoconstriction with an increase in CVP and thus an increase in cardiac output and blood pressure. Parasympathetic activity (vagal tone) decreases, contributing to the rise in heart rate.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 40
Incorrect
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Which of the following statements is incorrect regarding the electron transfer system?
Your Answer: The electron transfer system is located on the cristae of the mitochondrion.
Correct Answer: The electron transfer system occurs in anaerobic respiration.
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 NADH2molecules 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 41
Incorrect
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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: Selective adrenal venous sampling
Correct 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 42
Correct
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Which of these is NOT a naturally occurring anticoagulant:
Your Answer: Factor V Leiden
Explanation:It’s crucial that thrombin’s impact is restricted to the injured site. Tissue factor pathway inhibitor (TFPI), which is produced by endothelial cells and found in plasma and platelets, is the first inhibitor to function. It accumulates near the site of harm induced by local platelet activation. Xa and VIIa, as well as tissue factor, are inhibited by TFPI. Other circulating inhibitors, the most potent of which is antithrombin, can also inactivate thrombin and other protease factors directly. Coagulation cofactors V and VIII are inhibited by protein C and protein S. Tissue plasminogen activator (TPA) from endothelial cells facilitates fibrinolysis by promoting the conversion of plasminogen to plasmin.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 43
Incorrect
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Approximately what percentage of filtered bicarbonate is reabsorbed in the proximal tubule:
Your Answer: 50 - 60%
Correct Answer: 0.8
Explanation:Bicarbonate is freely filtered at the glomerulus. Less than 0.1% of filtered bicarbonate is normally excreted in the urine (if plasma [HCO3-] increases, maximum tubular transport is exceeded and some HCO3-is excreted in urine). About 80% of bicarbonate is reabsorbed in the proximal tubule. 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. A further 10 – 15% of HCO3-is similarly reabsorbed in the thick ascending limb of the loop of Henle. In the early distal tubule, H+secretion is predominantly by Na+/H+exchange but more distally, the Na+gradient is insufficient so secretion is via H+ATPase and H+/K+ATPase in intercalated cells, which contain plentiful carbonic acid. As secreted H+is derived from CO2, new HCO3-is formed and returns to the blood.H+secretion is proportional to intracellular [H+] which itself is related to extracellular pH. A fall in blood pH will therefore stimulate renal H+secretion. In the proximal tubule secretion of H+serves to reclaim bicarbonate from glomerular filtrate so it is not lost, but in the distal nephron, secretion leads to net acid excretion and generation of new bicarbonate.
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This question is part of the following fields:
- Physiology
- Renal
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Question 44
Incorrect
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Which of the following does NOT affect the rate of flow of a liquid through a tube:
Your Answer: Length of the tube
Correct Answer: Surface tension
Explanation:Flow through a tube is dependent upon:The pressure difference across the ends of the tube (P1– P2)The resistance to flow provided by the tube (R)This is Darcy’s law, which is analogous to Ohm’s law in electronics:Flow = (P1– P2) / RResistance in the tube is defined by Poiseuille’s law, which is determined by the diameter of the tube and the viscosity of the fluid. Poiseuille’s law is as follows:Resistance = (8VL) / (πR4)Where:V = The viscosity of the fluidL = The length of the tubeR = The radius of the tubeTherefore, in simple terms, resistance is directly proportional to the viscosity of the fluid and the length of the tube and inversely proportional to the radius of the tube. Of these three factors, the most important quantitatively and physiologically is vessel radius.It can be seen that small changes in the radius can have a dramatic effect on the flow of the fluid. For example, the constriction of an artery by 20% will decrease the flow by approximately 60%.Another important and frequently quoted example of this inverse relationship is that of the radius of an intravenous cannula. Doubling the diameter of a cannula increases the flow rate by 16-fold (r4). This is the reason the diameter of an intravenous cannula in resuscitation scenarios is so important.*Please note that knowledge of the detail of Poiseuille’s law is not a requirement of the RCEM Basic Sciences Curriculum.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 45
Incorrect
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Digoxin is predominantly used for which of the following:
Your Answer: Termination of supraventricular tachycardia associated with Wolff-Parkinson-White syndrome
Correct Answer: Rate control in persistent and permanent atrial fibrillation
Explanation:Digoxin is most useful for controlling the ventricular response in persistent and permanent atrial fibrillation and atrial flutter. Digoxin is usually only effective for controlling the ventricular rate at rest, and should therefore only be used as monotherapy in predominantly sedentary patients with non-paroxysmal atrial fibrillation. It is now rarely used for rapid control of heart rate, as even with intravenous administration, response may take many hours. Digoxin is reserved for patients with worsening or severe heart failure due to left ventricular systolic dysfunction refractory to combination therapy with first-line agents. Digoxin is contraindicated in supraventricular arrhythmias associated with accessory conduction pathways e.g. Wolff-Parkinson-White syndrome.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 46
Incorrect
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What is the mechanism of action of captopril:
Your Answer: Blockage of angiotensin II receptors
Correct 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 47
Incorrect
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Which of the following is an ECG change typically associated with hyperkalaemia:
Your Answer: Prominent U waves
Correct Answer: Wide QRS complex
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
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Question 48
Incorrect
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Fenestrated capillaries are typically found where in the body:
Your Answer: Reticuloendothelial system
Correct 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 49
Incorrect
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A 53 year old women presents to the emergency room with a chronic cough. The pulmonary receptors likely to be involved in causing her cough are:
Your Answer: Peripheral chemoreceptors
Correct Answer: Irritant receptors
Explanation:Throughout the airways, there are irritant receptors which are located between epithelial cells which are made of rapidly adapting afferent myelinated fibres in the vagus nerve. A cough is as a result of receptor stimulation located in the trachea, hyperpnoea is as a result of receptor stimulation in the lower airway. Stimulation may also result in reflex bronchial and laryngeal constriction. Many factors can stimulate irritant receptors. These include irritant gases, smoke and dust, airway deformation, pulmonary congestion, rapid inflation/deflation and inflammation. Deep augmented breaths or sighs seen every 5 – 20 minutes at rest are due to stimulation of these irritant receptors. This reverses the slow lung collapse that occurs in quiet breathing.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 50
Incorrect
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Regarding water and electrolyte absorption in the small intestine, which of the following statements is INCORRECT:
Your Answer:
Correct Answer: Na+ enters the cell across the apical membrane against its concentration gradient by both membrane channels and transporter protein mechanisms.
Explanation:As the contents of the intestine are isotonic with body fluids and mostly have the same concentration of the major electrolytes, their absorption is active. Water cannot be moved directly, but follows osmotic gradients set up by the transport of ions, primarily mediated by the sodium pump.Na+/K+ ATPase located on the basolateral membrane of the epithelial cells pumps three Na+ ions from the cell in exchange for two K+ ions, against their respective concentration gradients. This leads to a low intracellular concentration of Na+ and a high intracellular concentration of K+. The low intracellular concentration of Na+ ensures a movement of Na+ from the intestinal contents into the cell down its concentration gradient by both membrane channels and transporter protein mechanisms. Na+ is then rapidly pumped again by the basolateral sodium pump. K+ leaves the cell across the basolateral membrane down its concentration gradient linked to an outward movement of Cl- against its concentration gradient (Cl- having entered the cell across the luminal membrane down its concentration gradient).
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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SESSION STATS - PERFORMANCE PER SPECIALTY
