Physiology of the Kidneys 617
- Antidiuretic hormone promotes the retention of water by
stimulating
a. the active transport of water.
b. the active transport of chloride.
c. the active transport of sodium.
d. the permeability of the collecting duct to water.
- Aldosterone stimulates sodium reabsorption and potassium
secretion in
a. the proximal convoluted tubule.
b. the descending limb of the loop.
c. the ascending limb of the loop.
d. the cortical collecting duct.
- Substance X has a clearance greater than zero but less than
that of inulin. What can you conclude about substance X?
a. It is not filtered.
b. It is filtered, but neither reabsorbed nor secreted.
c. It is filtered and partially reabsorbed.
d. It is filtered and secreted.
- Substance Y has a clearance greater than that of inulin. What
can you conclude about substance Y?
a. It is not filtered.
b. It is filtered, but neither reabsorbed nor secreted.
c. It is filtered and partially reabsorbed.
d. It is filtered and secreted.
- About 65% of the glomerular ultrafiltrate is reabsorbed in
a. the proximal tubule.
b. the distal tubule.
c. the loop of Henle.
d. the collecting duct.
- Diuretic drugs that act in the loop of Henle
a. inhibit active sodium transport.
b. cause an increased flow of filtrate to the distal convoluted
tubule.
c. cause an increased secretion of potassium into the tubule.
d. promote the excretion of salt and water.
e. do all of these.
- The appearance of glucose in the urine
a. occurs normally.
b. indicates the presence of kidney disease.
c. occurs only when the transport carriers for glucose
become saturated.
d. is a result of hypoglycemia.
- Reabsorption of water through the tubules occurs by
a. osmosis.
b. active transport.
c. facilitated diffusion.
d. all of these.
- Which of these factors oppose(s) filtration from the
glomerulus?
a. plasma oncotic pressure
b. hydrostatic pressure in glomerular (Bowman’s) capsule
c. plasma hydrostatic pressure
d. both a and b
e. both b and c
- The countercurrent exchange in the vasa recta
a. removes Na^1 from the extracellular fluid.
b. maintains high concentrations of NaCl in the extracellular
fluid.
c. raises the concentration of Na^1 in the blood leaving the
kidneys.
d. causes large quantities of Na^1 to enter the filtrate.
e. does all of these.
- The kidneys help to maintain acid-base balance by
a. the secretion of H^1 in the distal regions of the nephron.
b. the action of carbonic anhydrase within the apical cell
membranes.
c. the action of carbonic anhydrase within the cytoplasm of
the tubule cells.
d. the buffering action of phosphates and ammonia in the
urine.
e. all of these means.
- Scientists currently believe that the main barrier to the
filtration of proteins into the glomerular capsule is the
a. capillary fenestrae.
b. basement membrane.
c. slit diaphragm.
d. macula densa.
- A drug that blocks the action of the organic anion
transporters would
a. increase the secretion of xenobiotics into the filtrate.
b. keep antibiotics in the blood for a longer time.
c. prevent glucose from being reabsorbed.
d. cause proteinuria to occur.
Test Your Understanding
- Explain how glomerular ultrafiltrate is produced and why it
has a low protein concentration.
- Describe the transport properties of the loop of Henle
and explain the interactions between the ascending and
descending limbs in the countercurrent multiplier system.
What is the functional significance of this system?
- Explain how countercurrent exchange occurs in the
vasa recta and discuss the functional significance of this
mechanism.
- Explain how an increase in ADH secretion promotes
increased water reabsorption and how water reabsorption
decreases when ADH secretion is decreased.
