1) Why is there a concentration gradient of NaCl in the medulla? A) There is mor
ID: 225350 • Letter: 1
Question
1) Why is there a concentration gradient of NaCl in the medulla?
A) There is more NaCl as the filtrate leaves then ascending limb compared to when it enters the ascending limb.
B) Passive transport in the ascending limb helps to establish an ion gradient.
C) The water in the medulla dilutes the NaCl to help contribute to the gradient.
D) There is more NaCl at the start of the ascending limb that decreases as the filtrate moves up the limb.
2) In a human nephron, the countercurrent multiplier mechanism of the nephron loop achieves a maximum filtrate concentration of about 1200 mOsm/L. A kangaroo rat (living in desert conditions) has a much longer nephron loop that utilizes the same countercurrent multiplier mechanism. In the rat, the maximum filtrate concentration would be __________ compared to humans.
A) higher
B) lower
3) Which of the following statements best describes the function of the nephron loop?
A) The nephron loop uses active transport of NaCl to create a concentration gradient used to passively transport water.
B) The nephron loop uses active transport of NaCl to create a concentration gradient used to actively transport water.
C) The nephron loop uses passive transport of NaCl to create a concentration gradient used to actively transport water.
D) The nephron loop uses passive transport of NaCl to create a concentration gradient used to passively transport water.
Explanation / Answer
Ans 1 D There is more NaCl at the start of ascending limb that decreases as the filterate moves up.
NaCl enters in to the descending loop due to hypertonic medulla and the osmolarity becomes approx 1200 m osmol/l in loop of henle. The salt then passively moves out when filterate moves up and osmolality decreases.
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