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Question 1
Incorrect
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Atrial natriuretic peptide (ANP) is primarily produced in response to:
Your Answer: A decrease in intravascular fluid volume
Correct 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. -
This question is part of the following fields:
- Physiology
- Renal
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Question 2
Correct
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Regarding the renin-angiotensin-aldosterone system (RAAS), which of the following statements is CORRECT:
Your Answer: Angiotensin II has a predominant vasoconstrictor effect on the efferent arteriole.
Explanation:Angiotensin II constricts both the afferent and efferent arterioles, but preferentially increases efferent resistance. The net effect of the more prominent increase in efferent tone is that the intraglomerular pressure is stable or increased, thereby tending to maintain or even raise the GFR. Renin is produced by granular cells of the juxtaglomerular apparatus. Renin cleaves plasma angiotensinogen (produced in the liver) into angiotensin I. Angiotensin I is converted by angiotensin-converting enzyme (ACE) on pulmonary endothelial cells to angiotensin II. Angiotensin II acts to potentiate sympathetic activity (positive feedback).
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This question is part of the following fields:
- Physiology
- Renal
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Question 3
Correct
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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 4
Correct
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Which of the following causes increased aldosterone secretion:
Your Answer: Decreased blood volume
Explanation:Decreased blood volume stimulates the secretion of renin (because of decreased renal perfusion pressure) and initiates the renin-angiotensin-aldosterone cascade. Angiotensin-converting enzyme (ACE) inhibitors block the cascade by decreasing the production of angiotensin. Hyperosmolarity stimulates antidiuretic hormone (ADH) [not aldosterone] secretion. Hyperkalaemia, not hypokalaemia, directly stimulates aldosterone secretion by the adrenal cortex. ANP inhibits renin secretion, thereby inhibiting the production of angiotensin and aldosterone.
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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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Question 6
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 7
Correct
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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 vasoconstriction
Cause 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 respectively
Stimulate the sensation of thirst
Potentiate sympathetic activity (positive feedback)
Inhibit renin production by granular cells (negative feedback) -
This question is part of the following fields:
- Physiology
- Renal
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Question 8
Correct
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Regarding renal clearance, which of the following statements is CORRECT:
Your Answer: The MDRD equation uses plasma creatinine to estimate the GFR making an adjustment for age, sex and race.
Explanation:Clearance is defined as the volume of plasma that is cleared of a substance per unit time. Inulin clearance is the gold standard for measurement of GFR but creatinine clearance is typically used instead. Creatinine is freely filtered and not reabsorbed, but there is a little creatinine tubular secretion. In practice, GFR is usually estimated from the plasma creatinine using a formula e.g. the MDRD equation making an adjustment for age, sex and race.
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This question is part of the following fields:
- Physiology
- Renal
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Question 9
Incorrect
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Which of the following does not increase renal phosphate excretion?
Your Answer: Calcitonin
Correct 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 -
This question is part of the following fields:
- Physiology
- Renal
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Question 10
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 11
Correct
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Which of the following does NOT increase free ionised calcium levels:
Your Answer: Calcitonin
Explanation:Calcium homeostasis is primarily controlled by three hormones: parathyroid hormone, activated vitamin D and calcitonin.
Parathyroid hormone acts on the kidneys to increase calcium reabsorption in the distal tubule by activating Ca2+entry channels in the apical membrane and the Ca2+ATPase pump in the basolateral membrane (and to decrease phosphate reabsorption in the proximal tubule).
Activated vitamin D acts to increase calcium reabsorption in the distal tubule via activation of a basolateral Ca2+ATPase pump (and to increase phosphate reabsorption).
Calcitonin acts to inhibit renal reabsorption of calcium (and phosphate).
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This question is part of the following fields:
- Physiology
- Renal
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Question 12
Correct
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Loop diuretics primarily act on which Na+ transporter?
Your Answer: Na + /K + /2Cl - symporter
Explanation:The most potent diuretics are loop diuretics e.g. furosemide. They work by inhibiting the Na+/K+/2Cl-symporter in the thick ascending limb of the loop of Henle, which inhibits sodium, potassium, and chloride reabsorption. As a result, there is diuresis with loss of these electrolytes. There is a reduction in transcellular voltage difference, paracellular calcium and magnesium reabsorption.
The medullary interstitium becomes more concentrated by salt reabsorption in the ascending limb. Loop diuretics block this process and reduce the ability of the kidney to concentrate urine. In the collecting duct, there is increased sodium delivery to the principal cells, which increases potassium secretion in return for sodium reabsorption. -
This question is part of the following fields:
- Physiology
- Renal
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Question 13
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 14
Correct
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Na+ is reabsorbed via the Na+/K+/2Cl-symporter in which part of the loop of Henle?
Your Answer: Thick ascending limb
Explanation:In the thick ascending limb is the part of the loop of Henle in which there is active reabsorption of Na+and Cl- ions from the tubular fluid. This occurs via the Na+/K+/2Cl-symporter on the apical membrane.
This mechanism is by:
1. Na+ions are transported across the basolateral membrane by Na+pumps and the Cl-ions by diffusion.
2. K+leaks back into the tubular fluid via apical ROMK K+channels which creates a positive charge.
3. This positive charge drives the reabsorption of cations (Na+, K+, Ca2+, Mg2+) through paracellular pathways.
4. Due to the thick ascending limb being impermeable to water, the tubular fluid osmolality is reduced by ion reabsorption, the interstitial fluid osmolality is increased, and an osmotic difference is created. -
This question is part of the following fields:
- Physiology
- Renal
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Question 15
Correct
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A patient with a high potassium level is at risk of going into cardiac arrest. What changes in the ECG may indicate the incident of cardiac arrest in this patient?
Your Answer: Peaked T waves and broad QRS complex
Explanation:Severe hyperkalaemia can result in a heart attack or a life-threatening arrhythmia.
T waves become narrow-based, pointed, and tall if hyperkalaemia is not treated.
The QRS complex widens and eventually merges with the T wave, resulting in a classic sine-wave electrocardiogram. Ventricular fibrillation and asystole are likely to follow.
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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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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 17
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 conduit
Saline administration
Endocrine (hyperparathyroidism)
Diarrhoea
Carbonic anhydrase inhibitors (e.g. acetazolamide)
Ammonium chloride
Renal tubular acidosis
Spironolactone -
This question is part of the following fields:
- Physiology
- Renal
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Question 18
Correct
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An increased anion gap metabolic acidosis is typically caused by which of the following?
Your Answer: Propylene glycol overdose
Explanation:Causes of a raised anion gap acidosis can be remember using the mnemonic MUDPILES:
-Methanol
-Uraemia (in renal failure)
-Diabetic ketoacidosis
-Propylene glycol overdose
-Infection/Iron overdose/Isoniazid/Inborn errors of metabolism
-Lactic acidosis
-Ethylene glycol overdose
-Salicylate overdose -
This question is part of the following fields:
- Physiology
- Renal
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Question 19
Correct
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Which of the following is a clinical effect of hyperkalaemia:
Your Answer: Muscle weakness
Explanation:Clinical features of hyperkalaemia may include:
paraesthesia, muscle weakness or paralysis, cardiac conduction abnormalities and dysrhythmias.Clinical features of hypokalaemia may include:
muscle weakness, muscle cramps, rhabdomyolysis and myoglobinuria, ascending paralysis resulting in respiratory failure, constipation, gut ileus with distension, anorexia, nausea and vomiting, impaired ADH action with polyuria and polydipsia, ECG changes and cardiac arrhythmias. -
This question is part of the following fields:
- Physiology
- Renal
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Question 20
Correct
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Renal potassium excretion is promoted by all but which one of the following:
Your Answer: Increased intracellular magnesium
Explanation:Aldosterone: A rise in [K+] in the extracellular fluid of the adrenal cortex directly stimulates aldosterone release. Aldosterone promotes the synthesis of Na+/K+ATPases and the insertion of more Na+/K+ATPases into the basolateral membrane, and also stimulates apical sodium and potassium channel activity, overall acting to increase sodium reabsorption and potassium secretion.
pH changes: Potassium secretion is reduced in acute acidosis and increased in acute alkalosis. A higher pH increases the apical K+channel activity and the basolateral Na+/K+ATPase activity – both changes that promote K+secretion.
Flow rates: Increased flow rates in the collecting duct reduce K+concentration in the lumen and therefore enhance K+secretion. Increased flow also activates BK potassium channels, and ENaC channels which promote potassium secretion and sodium reabsorption respectively.
Sodium delivery: Decreased Na+delivery to the collecting ducts results in less Na+reabsorption and hence a reduced gradient for K+secretion.
Magnesium: Intracellular magnesium can bind and block K+channels inhibiting K+secretion into the tubules. Therefore magnesium deficiency reduces this inhibitory effect and so allows more potassium to be secreted into tubules and can cause hypokalaemia. -
This question is part of the following fields:
- Physiology
- Renal
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SESSION STATS - PERFORMANCE PER SPECIALTY
