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Renal Physiology — Advanced Review MCQs
MBBS Professional Review: Physiology · MBBS / Medicine · 40 practice questions
- Tubular Reabsorption - Segment-Specific Transporters
- Tubular Reabsorption and Secretion / Nephron Segments
- Concentration and Dilution of Urine
- Renin-Angiotensin-Aldosterone System
- Tubular Reabsorption and Secretion
- Acid-Base Regulation by the Kidney
- Glomerular Filtration
- Acid-Base Regulation - Cellular Mechanisms
1. A patient presents with chronic non-anion-gap metabolic acidosis and a urine pH of 6.2 that fails to acidify below 5.5 despite ongoing systemic acidemia. Which cellular defect best explains this presentation?
- AImpaired hydrogen ion secretion via H+-ATPase pumps in type A intercalated cells of the collecting duct
- BImpaired carbonic anhydrase activity in the proximal convoluted tubule
- CImpaired ammoniagenesis in the proximal tubule from glutamine metabolism
- DImpaired sodium-hydrogen exchange (NHE3) causing failure of proximal bicarbonate reabsorption
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A. Impaired hydrogen ion secretion via H+-ATPase pumps in type A intercalated cells of the collecting duct The text describes Type 1 (distal) RTA as resulting from impaired hydrogen ion secretion by type A intercalated cells, producing a non-anion-gap acidosis with urine pH persistently above 5.5.
2. Which of the following stimuli would be expected to directly increase renin secretion from the juxtaglomerular cells, according to the described regulatory pathways?
- AIncreased renal perfusion pressure
- BIncreased sympathetic activity acting via beta-1 adrenergic receptors
- CIncreased circulating angiotensin II acting on efferent arterioles
- DIncreased sodium delivery to the macula densa
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B. Increased sympathetic activity acting via beta-1 adrenergic receptors The text lists decreased perfusion pressure, decreased sodium delivery to the macula densa, and increased sympathetic activity via beta-1 receptors as stimuli for renin release; only increased sympathetic activity among the options matches a listed stimulus.
3. Which statement best describes how the vasa recta contribute to the kidney's urine-concentrating mechanism, in contrast to the loop of Henle's role in generating the medullary gradient?
- AThe vasa recta passively exchange water and solutes as countercurrent exchangers, preserving the gradient generated by the loop of Henle rather than creating it
- BThe vasa recta actively transport sodium and chloride to establish the medullary osmotic gradient de novo
- CThe vasa recta dissipate the medullary gradient to allow rapid excretion of concentrated urine
- DThe vasa recta are impermeable to water, forcing solute reabsorption to occur exclusively in the ascending limb
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A. The vasa recta passively exchange water and solutes as countercurrent exchangers, preserving the gradient generated by the loop of Henle rather than creating it The text distinguishes the loop of Henle (which actively generates the gradient via the countercurrent multiplier) from the vasa recta, which function as passive countercurrent exchangers that preserve rather than dissipate this gradient.
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