Course: Physiology Thread Topic: Production Of Concentrated And Diluted Urine

Question 1

Select the single best answer to the numbered question.

Which of the following statements about the production of concentrated urine is NOT true?


A. The accumulation of NaCl in the medullary interstitium depends on the active reabsorption of NaCl by the thick ascending limb.
B. Countercurrent multiplication in the vasa recta helps to prevent washout of the medullary gradients of NaCl and urea.
C. In the presence of ADH urea is reabsorbed from the inner medullary collecting ducts.
D. The descending limb of the loop of Henle is permeable to water.
E. In the presence of high levels of ADH, about 50% of the osmolality of the interstitum of the inner medulla is due to NaCl.
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Question 2

Select the single best answer to the numbered question.

Which of the following statements about the renal concentrating mechanism is NOT correct?


A. The active reabsorption of NaCl in the thick ascending limb is known as the single effect.
B. The TAL can create a gradient of NaCl between tubular fluid and medullary interstitium of about 200 mosmolal at a given depth in the medulla.
C. As fluid descends in the descending limb, water is osmotically withdrawn and NaCl in the tubular fluid becomes concentrated.
D. As fluid ascends in the thin ascending limb, Na+ and Cl are passively reabsorbed.
E. Fluid leaving the TAL is approximately iso-osmotic to plasma.
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Question 3

Select the single best answer to the numbered question.

Which of the following statements about the renal concentrating mechanism is NOT correct?


A. In the presence of ADH, fluid in the later part of the distal tubule and the cortical collecting duct is hypo-osmotic with respect to plasma.
B. In the presence of ADH, urea is reabsorbed from the inner medullary collecting duct and accumulates there to a level of approximately 600 mM.
C. In the absence of ADH, the level of urea in the inner medullary interstitium declines.
D. The total solute excretion rate tends to remain relatively constant in the face of large changes in urine volume and urine osmolality.
E. In the absence of ADH, the osmolality of urine is less than the osmolality of fluid in the cortical collecting duct.
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Question 4

Select the single best answer to the numbered question.

Which of the following statements about the concentration of Na+ in the tubular fluid is NOT true?


A. In the proximal tubule, it is normally approximately equal to that in plasma.
B. In the thick ascending limb of Henle, it is normally less than that in plasma.
C. In the first part of the distal tubule, Na+ concentration is equal to that in plasma when ADH is present.
D. In the absence of ADH, Na+ concentration in the beginning of the collecting duct is less than that in plasma.
E. In the absence of ADH, Na+ concentration falls as fluid progresses down the collecting duct.
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Question 5

Select the single best answer to the numbered question.

Which of the following statements about ADH is NOT true?


A. Osmoreceptors in the supraoptic and paraventricular nuclei respond to hypertonicity by increasing ADH release.
B. Alcohol causes diuresis by inhibiting ADH release.
C. Hyperosmolality stimulates both ADH release and thirst.
D. ADH inhibits the action of aldosterone to promote salt and water reabsorption in the distal tubule.
E. ADH increases the water permeability of the lumenal membrane of the later part of the distal tubule and the collecting duct by causing more water channel proteins to be inserted in these membranes.
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Question 6

Select the single best answer to the numbered question.

Which of the following statements about the urine concentrating mechanism in the renal medulla is NOT true?


A. In the thick ascending limb, Cl- entry into the cells via the Na, K, 2Cl transporter allows this transporter to be electroneutral.
B. The water permeability of the descending limb is higher than that of the ascending limb.
C. The deeper in the medulla, the higher the NaCl concentration.
D. In the presence of ADH the total osmolality of the interstitial fluid near the tip of the renal papilla is reduced.
E. Animals with longer loops of Henle can produce more concentrated urine.
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Question 7

Select the single best answer to the numbered question.

Which of the following statements about renal handling of urea is NOT true?


A. Urea deposited in the inner medulla plays a role in the mechanism by which the kidney produces hyperosmotic urine.
B. Urea reabsorbed in the inner medullary collecting ducts enters the tubular fluid in the loops of Henle.
C. In the presence of ADH, urea is concentrated in the late distal tubule and the cortical collecting ducts when water is absorbed there.
D. In the absence of ADH, there is less deposition of urea in the inner medulla.
E. When there is a high flow rate in the inner medullary collecting ducts, there is a high rate of urea reabsorption there.
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Question 8

Select the single best answer to the numbered question.

Which of the following statements about production of concentrated and dilute urine is NOT true?


A. The range of osmolality of urine that a normal human can produce is from 50 mosmoles/liter with no ADH to 1200 mosmoles/liter with maximal levels of ADH.
B. The ability to produce a concentrated urine, but not the ability to produce a dilute urine, depends on the reabsorption of NaCl by the thick ascending limb of the loop of Henle (the TAL).
C. Countercurrent multiplication of NaCl, but not urea, occurs in the loop of Henle.
D. Deposition of urea in the interstitium of the inner medulla depends on the presence of ADH.
E. In the presence of maximal ADH, the osmolality of NaCl in the inner medullary interstitium is about equal to the osmolality of urea there.
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Question 9

Select the single best answer to the numbered question.

Which of the following statements of diuretics is NOT true?


A. Loop diuretics may cause hypokalemia
B. Carbonic anhydrase inhibitors may contribute to metabolic acidosis.
C. The target of loop diuretics is the reabsorption of Na+ by the electrogenic Na+ channels in the luminal plasma membrane of the TAL.
D. Potassium sparing diuretics decrease Na+ transport across the luminal plasma membranes of principal cells of the late distal tubule and collecting duct.
E. Potassium sparing diuretics do not produce a large increase in urine flow rate.
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