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Question 1
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 2
Incorrect
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Which of the following causes increased aldosterone secretion:
Your Answer: Administration of an ACE inhibitor
Correct 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. ANPÂ 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 3
Correct
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Molecules with a molecular weight of less than which of the following are filtered freely at the glomerular filtration barrier:
Your Answer: 7000 Da
Explanation:Molecular weight is the main factor in determining whether a substance is filtered or not – molecules < 7 kDa in molecular weight are filtered freely e.g. glucose, amino acids, urea, ions but larger molecules are increasingly restricted up to 70 kDa, above which filtration is insignificant. Negatively charged molecules are further restricted, as they are repelled by negative charges, particularly in the basement membrane. Albumin has a molecular weight of 69 kDa and is negatively charged, thus only very small amounts are filtered (and all of the filtered albumin is reabsorbed in the proximal tubule), whereas small molecules such as ions, glucose, amino acids and urea pass the filter without hindrance. This means that ultrafiltrate is virtually protein free, but otherwise has an identical composition of that of plasma. The epithelial lining of the Bowman's capsule consists of a single layer of cells called podocytes. The glomerular capillary endothelium is perforated by pores (fenestrations) which allow plasma components with a molecular weight of < 70 kDa to pass freely.
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This question is part of the following fields:
- Physiology
- Renal
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Question 4
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 5
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 6
Correct
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Question 7
Correct
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How is filtered K+mainly reabsorbed in the thick ascending limb of the loop of Henle:
Your Answer: Secondary active transport via Na + /K + /2Cl - cotransporter
Explanation:Around 30% of filtered K+is reabsorbed in the thick ascending limb of the loop of Henle, primarily via the luminal Na+/K+/2Cl-cotransporter, but there is also significant paracellular reabsorption, encouraged by the positive potential in the tubular lumen.
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This question is part of the following fields:
- Physiology
- Renal
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Question 8
Correct
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The renal corpuscle, consisting of the Bowman's capsule and the glomerulus is found where in the kidney:
Your Answer: The cortex
Explanation:All nephrons have their renal corpuscles in the renal cortex. Cortical nephrons have their renal corpuscles in the outer part of the cortex and relatively short loops of Henle. Juxtamedullary nephrons have their corpuscles in the inner third of the cortex, close to the corticomedullary junction, with long loops of Henle extending into the renal medulla.
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This question is part of the following fields:
- Physiology
- Renal
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Question 9
Correct
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Water is reabsorbed in which portion of the Henle loop:
Your Answer: Thin descending limb
Explanation:The loop of Henle consists of three functionally distinct segments: the thin descending segment, the thin ascending segment, and the thick ascending segment. About 20 percent of the filtered water is reabsorbed in the loop of Henle and almost all of this occurs in the thin descending limb. Na+ and Cl-ions are actively reabsorbed from the tubular fluid in the thick ascending limb via the Na+/K+/2Cl-symporter on the apical membrane. Because the thick ascending limb is water-impermeable, ion reabsorption lowers tubular fluid osmolality while raising interstitial fluid osmolality, resulting in an osmotic difference. Water moves passively out of the thin descending limb as the interstitial fluid osmolality rises, concentrating the tubular fluid. This concentrated fluid descends in the opposite direction of fluid returning from the deep medulla still higher osmolality areas.
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This question is part of the following fields:
- Physiology
- Renal
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Question 10
Correct
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Which of the following is an ECG change typically associated with hyperkalaemia:
Your 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 abnormalities
K+>6.5 mmol/l – P waves widen and flatten, PR segment lengthens, P waves eventually disappear
K+>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. -
This question is part of the following fields:
- Physiology
- Renal
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Question 11
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 12
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 13
Correct
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Question 14
Incorrect
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Which of the following does NOT increase free ionised calcium levels:
Your Answer: Activated vitamin D
Correct 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 15
Correct
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Atrial natriuretic peptide (ANP) is primarily produced in response to:
Your Answer: An increase in intravascular fluid volume
Explanation:Atrial natriuretic peptide (ANP) is released from cardiac atrial muscle cells in response to atrial stretch caused by an increase in intravascular fluid volume and is also produced in collecting duct cells.
Atrial natriuretic peptide acts to inhibit sodium reabsorption in the distal nephron. -
This question is part of the following fields:
- Physiology
- Renal
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Question 16
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 17
Correct
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The correct statement about the glomerular filtration barrier is which of the following?
Your Answer: The basement membrane is negatively charged, restricting filtration of negatively charged molecules.
Explanation:The main factor in determining whether a substance is filtered or not is molecular weight. Molecules < 7 kDa in molecular weight e.g. glucose, amino acids, urea, ions are filtered freely, but larger molecules are increasingly restricted up to 70 kDa, and there is very little filtration for anything above this.
There is further restriction of negatively charged molecules because they are repelled by negative charges, particularly in the basement membrane. Albumin, which has a molecular weight of 69 kDa and is negatively charged, is filtered but only in very small amounts. All of the filtered albumin is reabsorbed in the proximal tubule. Small molecules such as ions, glucose, amino acids and urea pass the filter without hindrance. Other than the ultrafiltrate being essentially protein free, it has an otherwise identical composition of plasma. Bowman’s capsule consists of:
– an epithelial lining which consists of a single layer of cells called podocytes
– endothelium which is perforated by pores or fenestrations – this allows plasma components with a molecular weight of < 70 kDa to pass freely. -
This question is part of the following fields:
- Physiology
- Renal
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Question 18
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 19
Correct
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The role of the juxtaglomerular (granular) cells of the juxtaglomerular apparatus is:
Your Answer: Production of renin
Explanation:Juxtaglomerular cells synthesise renin. These cells are specialised smooth muscle cells that are located in the walls of the afferent arterioles, and there are some in the efferent arterioles.
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This question is part of the following fields:
- Physiology
- Renal
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Question 20
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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SESSION STATS - PERFORMANCE PER SPECIALTY
