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Question 1
Correct
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What is the primary function of the mitochondria?
Your Answer: The production of the cell's supply of chemical energy
Explanation:The mitochondria is responsible for the production of the cell’s supply of chemical energy. It does this by using molecular oxygen, sugar and small fatty acid molecules to generate adenosine triphosphate (ATP) by a process ss known as oxidative phosphorylation. An enzyme called ATP synthase is required. Transcription of ribosomal RNA occurs in the nucleolusProduction of messenger RNA occur in the nucleusProduction of lysosome occurs in the Golgi apparatusThe post-translational processing of newly made proteins occurs in the endoplasmic reticulum
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This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 2
Incorrect
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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 3
Correct
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If the afferent arteriole's diameter is smaller than the efferent arteriole's diameter in the glomerulus:
Your Answer: The net filtration pressure will decrease
Explanation:The relative resistance of the afferent and efferent arterioles substantially influences glomerular capillary hydrostatic pressure and consequently GFR. Filtration is forced through the filtration barrier due to high pressure in the glomerular capillaries. Afferent arteriolar constriction lowers this pressure while efferent arteriolar constriction raises it.
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This question is part of the following fields:
- Physiology
- Renal
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Question 4
Correct
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Regarding airway resistance, which of the following statements is INCORRECT:
Your Answer: In the lower respiratory tract, airway resistance is mostly determined by the smallest bronchioles.
Explanation:Airway resistance is primarily determined by the airway radius according to Poiseuille’s law, and whether the flow is laminar or turbulent. The major site of airway resistance is the medium-sized bronchi. The smallest airways would seem to offer the highest resistance, but they do not because of their branching parallel arrangement.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 5
Correct
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Regarding fluid balance, which of the following statements is CORRECT:
Your Answer: About three-quarters of extracellular fluid is interstitial.
Explanation:An ‘average’ person (70 kg male) contains about 40 litres of water in total, separated into different fluid compartments by biological semipermeable membranes; plasma cell membranes between extracellular and intracellular fluid, and capillary walls between interstitial and intravascular fluid. Around two-thirds of the total fluid (27 L) is intracellular fluid (ICF) and one-third of this (13 L) is extracellular fluid (ECF). The ECF can be further divided into intravascular fluid (3.5 L) and interstitial fluid (9.5 L). Transcellular fluid refers to any fluid that does not contribute to any of the main compartments but which are derived from them e.g. gastrointestinal secretions and cerebrospinal fluid, and has a collective volume of approximately 2 L.Osmosis is the passive movement of water across a semipermeable membrane from regions of low solute concentration to those of higher solute concentration.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 6
Correct
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All of the following statement are correct regarding endothelium derived nitric oxide except:
Your Answer: Nitric oxide production is inhibited by local mediators such as bradykinin, histamine and serotonin.
Explanation:Factors that elevate intracellular Ca2+ increase nitric oxide (NO) production by the endothelium included local mediators such as histamine and serotonin, bradykinin, and some neurotransmitters like substance P. NO production is also stimulated by increased flow (shear stress) and additionally activates prostacyclin synthesis. As a result of basal production of NO, there is continuous modulation of vascular resistance and as a result, there is increased production of nitric oxide acts which causes vasodilation. Platelet activation and thrombosis are inhibited by nitric oxide.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 7
Correct
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A somatostatinoma is diagnosed in a 74-year-old patient who has recently developed diabetes mellitus, recurrent episodes of gallstones, and Steatorrhoea. She also has a tumour in the head of her pancreas.Which of the following is the most likely effect of this tumour?
Your Answer: Inhibit gastric acid secretion
Explanation:Somatostatin-producing cells present in the pyloric antrum, duodenum, and pancreatic islets are known as D-cells or delta-cells. Somatostatin inhibits gastric acid secretion by acting directly on acid-producing parietal cells in the stomach via a G-protein coupled receptor.Somatostatin affects hormones in the following ways:Inhibits the anterior pituitary’s secretion of growth hormone.Inhibits the anterior pituitary’s secretion of thyroid-stimulating hormone.The secretion of various gastrointestinal hormones is inhibited (including gastrin, CCK, secretin, motilin, VIP and GIP) Reduces the rate at which the stomach empties.Inhibits the release of insulin and glucagon from the pancreas.The pancreas’ exocrine secretory activity is inhibited.Somatostatin can also slow the digestive process by suppressing the production of hormones such gastrin, secretin, and histamine, which reduces gastric acid secretion.A somatostatinoma is a cancerous tumour of the endocrine pancreas’ D-cells, which make somatostatin. Somatostatin inhibits pancreatic and gastrointestinal hormones when levels are high. The following clinical characteristics are related with somatostatinomas:Insulin secretion blockage causes diabetes mellitus.Gallstones by inhibition of CCK and secretin Steatorrhoea via inhibition of CCK and secretinHypochlorhydria is caused by the suppression of gastrin, a hormone that increases gastric acid output regularly.
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This question is part of the following fields:
- Gastrointestinal Physiology
- Physiology
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Question 8
Correct
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All of the following statement about the microcirculation are correct except:
Your Answer: Over the capillary bed, there is a net absorption of fluid.
Explanation:The hydrostatic pressure along the length of the capillary is usually greater than plasma oncotic pressure. As a result, there is a small net filtration of fluid from the capillary into the interstitial space. The regulation of blood flow into the microcirculation is via the vasoconstriction of small arterioles, which is activated by the sympathetic nervous system through numerous nerve endings in their walls. Unlike proteins, most ions and small molecules diffuse easily across capillary walls and thus the crystalloid osmotic pressure they exert is roughly the same on either side of the capillary wall. Because the plasma colloid osmotic pressure is higher than interstitial colloid osmotic, fluid is drawn intravascularly. A reduction of hydrostatic capillary pressure and transient increase in absorption of fluid is a result of arteriolar constriction.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 9
Incorrect
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What is the effect of activated vitamin D on the renal handling of calcium:
Your Answer: Increases calcium reabsorption in the proximal tubule
Correct Answer: Increases calcium reabsorption in the distal tubule
Explanation:Activated vitamin D acts to:GUT:increase calcium and phosphate absorption in the small intestine (the main action)KIDNEYS:increase renal calcium reabsorption (in the distal tubule via activation of a basolateral Ca2+ATPase pump), increase renal phosphate reabsorption, inhibit 1-alpha-hydroxylase activity in the kidneys (negative feedback)PARATHYROID GLANDS:inhibit PTH secretion from the parathyroid glands
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 10
Correct
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Which of the following is NOT a function of the commensal intestinal bacterial flora:
Your Answer: Breakdown of haem into bilirubin
Explanation:Commensal intestinal bacterial flora have a role in:Keeping pathogenic bacteria at bay by competing for space and nutrientConverting conjugated bilirubin to urobilinogen (some of which is reabsorbed and excreted in urine) and stercobilinogen which is excreted in the faecesThe synthesis of vitamins K, B12, thiamine and riboflavinThe breakdown of primary bile acids to secondary bile acidsThe breakdown of cholesterol, some food additives and drugs
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 11
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 12
Correct
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Question 13
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 14
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 15
Incorrect
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Action potentials are transmitted from myocyte to myocyte via which of the following:
Your Answer: Desmosomes
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 16
Incorrect
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Regarding antacids, which of the following statements is CORRECT:
Your Answer: Magnesium carbonate tends to cause constipation.
Correct Answer: Antacids are contraindicated in hypophosphataemia.
Explanation:Antacids are contraindicated in hypophosphataemia. Liquid preparations are more effective than tablet preparations. Magnesium-containing antacids tend to be laxative whereas aluminium-containing antacids tend to be constipating. Antacids are best taken when symptoms occur or are expected, usually between meals and at bedtime. Antacids should preferably not be taken at the same time as other drugs since they may impair absorption.
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This question is part of the following fields:
- Gastrointestinal
- Pharmacology
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Question 17
Correct
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The only statement that is correct regarding diffusion is which of the following?
Your Answer: The permeability of a membrane is related to the membrane thickness and composition.
Explanation:Passive diffusion is a process that describes the movement down a concentration gradient. This process accounts for movement across small distances like within the cytosol or across membranes. Factors that affect the diffusion of a substance across a membrane are the permeability (p) of the membrane, a difference in concentration across the membrane and the membrane area over which diffusion occurs. The membrane thickness and composition, and the diffusion coefficient of the substance also affects the permeability. Fick’s law describes the rate of diffusion of a substance within a solution, which can be modified to describe the rate of diffusion across a membrane.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 18
Correct
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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 19
Correct
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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 20
Correct
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Question 21
Correct
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A 70 year old man who has a previous history of small cell lung cancer was found to have severe hyponatraemia on a recent blood test and he is sent to the emergency room. In the nephron, where is the likely cause of this abnormality?
Your Answer: Distal nephron
Explanation:In the cancer patient, hyponatremia is usually caused by the syndrome of inappropriate antidiuretic hormone (SIADH). This develops more frequently with small cell lung cancer (SCLC) than with other malignancies. The pathogenesis of this is as a result of the process whereby ADH binds V2 receptors on renal principal cells in the late distal tubule and collecting ducts, resulting in elevation of cAMP levels. Increased cAMP levels cause fusion of intracellular vesicles with the apical membrane. There are water channels called aquaporins in their membranes of these vesicles, and these increase the water permeability, thus facilitating increased water reabsorption and urine concentration. Thus, by increasing water retention, ADH causes blood to be diluted, which then decreases the concentration of solutes like sodium.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 22
Correct
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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 23
Correct
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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 24
Incorrect
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Regarding pressures and airflow during the normal breathing cycle, which of the following statements is INCORRECT:
Your Answer: During expiration both intrapleural pressure and alveolar pressure rise.
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 25
Correct
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Regarding cardiac excitation-contraction coupling, which of the following statements is CORRECT:
Your 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 26
Incorrect
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A 32-year-old woman diagnosed with hyperthyroidism has her T 4 levels grossly elevated and she is started on carbimazole.A release of which of the following from the hypothalamus is inhibited by increase in T4 levels?
Your Answer: Thyroid-stimulating hormone
Correct Answer: Thyrotropin-releasing hormone
Explanation:A negative feedback mechanism involving the hypothalamic-pituitary-thyroid axis controls the release of T3 and T4 into the bloodstream. When metabolic rate is low or serum T3 and/or T4 levels are decrease, this triggers the secretion of thyrotropin-releasing hormone (TRH) from the hypothalamus.TRH goes to the anterior pituitary gland and stimulates secretion of thyroid-stimulating hormone (TSH). An increased serum level of T3 and T4 inhibits the release of TRH.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 27
Correct
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In the treatment of hypertensive episodes in pheochromocytoma, which of the following medication types is administered as first-line management:
Your Answer: Alpha-blockers
Explanation:The first line of management in controlling blood pressure and preventing intraoperative hypertensive crises is to use a combination of alpha and beta-adrenergic inhibition. In phaeochromocytoma, alpha-blockers are used to treat hypertensive episodes in the short term. Tachycardia can be managed by the careful addition of a beta-blocker, preferably a cardioselective beta-blocker, once alpha blockade has been established. Long term management of pheochromocytoma involves surgery.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 28
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 29
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 30
Correct
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The following all cause a left shift in the oxygen dissociation curve EXCEPT for:
Your Answer: Decrease in pH
Explanation:An increased affinity of haemoglobin for oxygen, shown by a left shift in the oxygen dissociation curve, is caused in the lungs by a rise in pH, a fall in PCO2,a decrease in temperature and a decrease in 2,3 -DPG. Carbon monoxide (CO) binds 240 times more strongly than O2to haemoglobin and by occupying O2-binding sites, reduces oxygen capacity. CO also increases oxygen affinity, shifting the oxygen haemoglobin curve to the left and making O2release to tissues more difficult.
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This question is part of the following fields:
- Physiology
- Respiratory
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SESSION STATS - PERFORMANCE PER SPECIALTY
