Concept Check Chapter 20 Silverthorn Questions:
1. Does the apical membrane of a collecting duct cell have more water pores when
vasopressin is present or when it is absent?
2. People who inherit vasopressin V2 receptor deficiency will have urine that is dilute or
concentrated?
3. A scientist monitoring the activity of osmoreceptors notices that infusing of
hyperosmotic saline (NaCl) causes increased firing of the osmoreceptors. Infusion of
hyperosmotic urea (a penetrating solute) [p.163] had no effect on the firing rate. If
osmoreceptors fire only when cell volume decreases, explain why hyperosmotic urea
did not affect them.
4. If vasopressin increases water reabsorption by the nephron, would vasopressin
secretion be increased or decreased with dehydration?
5. Experiments suggest that there are peripheral osmoreceptors in the lumen of the
upper digestive tract and in the hepatic portal vein [Fig. 14.1, p. 471]. What is the
adaptive significance of osmoreceptors in these locations?
6. Explain why patients taking a loop diuretic that inhibits solute reabsorption excrete
greater-than-normal volumes of urine.
7. Loop diuretics that inhibit the NKCC symporter are sometimes called “potassium-
wasting” diuretics. Explain why people who are on loop diuretics must increase their
dietary K+ intake.
8. In Figure 20.9b, what forces cause Na+ and K+ to cross the apical membrane?
9. If a person experiences hyperkalemia, what happens to resting membrane potential
and the excitability of neurons and the myocardium?
10. Laboratory values for ions may be reported as mg/L, mmol/L, or mEq/L. If normal
plasma Na+ is 140 mmol/L, what is that concentration expressed as mEq/L? [Fig. 2.7,
p.78].
11. A man comes to the doctor with high blood pressure. Tests show that he also has
elevated plasma renin levels and atherosclerotic plaques that have nearly blocked
blood flow through his renal arteries. How does decreased blood flow in his renal
arteries cause elevated renin levels?
12. Map the pathways through which elevated renin causes high blood pressure in the
man mentioned in Concept Check 11.
13. Why is it more efficient to put ACE in the pulmonary vasculature than in the systemic
vasculature?
14. Incorporate the thirst reflex into Figure 20.8.
15. Map the pathway that begins with renal artery stenosis and ends with hypertension.
(Hint: It involves the RAAS pathway.)
16. In equation 6, the amount of HCO3- present is increased at equilibrium. Why doesn’t
this HCO3- act as a buffer and prevent acidosis from occurring?
17. Why is ATP required for H+ secretion by the H+-K+ transporter but not for the Na+-H+
exchanger?
18. In hypokalemia, the intercalated cells of the distal nephron reabsorb K+ from the
tubule lumen. What happens to blood pH as a result?
Concept Check Chapter 20 Answers:
1. More water pores when vasopressin is present.
2. If vasopressin action is suppressed, the urine is dilute.
1. Does the apical membrane of a collecting duct cell have more water pores when
vasopressin is present or when it is absent?
2. People who inherit vasopressin V2 receptor deficiency will have urine that is dilute or
concentrated?
3. A scientist monitoring the activity of osmoreceptors notices that infusing of
hyperosmotic saline (NaCl) causes increased firing of the osmoreceptors. Infusion of
hyperosmotic urea (a penetrating solute) [p.163] had no effect on the firing rate. If
osmoreceptors fire only when cell volume decreases, explain why hyperosmotic urea
did not affect them.
4. If vasopressin increases water reabsorption by the nephron, would vasopressin
secretion be increased or decreased with dehydration?
5. Experiments suggest that there are peripheral osmoreceptors in the lumen of the
upper digestive tract and in the hepatic portal vein [Fig. 14.1, p. 471]. What is the
adaptive significance of osmoreceptors in these locations?
6. Explain why patients taking a loop diuretic that inhibits solute reabsorption excrete
greater-than-normal volumes of urine.
7. Loop diuretics that inhibit the NKCC symporter are sometimes called “potassium-
wasting” diuretics. Explain why people who are on loop diuretics must increase their
dietary K+ intake.
8. In Figure 20.9b, what forces cause Na+ and K+ to cross the apical membrane?
9. If a person experiences hyperkalemia, what happens to resting membrane potential
and the excitability of neurons and the myocardium?
10. Laboratory values for ions may be reported as mg/L, mmol/L, or mEq/L. If normal
plasma Na+ is 140 mmol/L, what is that concentration expressed as mEq/L? [Fig. 2.7,
p.78].
11. A man comes to the doctor with high blood pressure. Tests show that he also has
elevated plasma renin levels and atherosclerotic plaques that have nearly blocked
blood flow through his renal arteries. How does decreased blood flow in his renal
arteries cause elevated renin levels?
12. Map the pathways through which elevated renin causes high blood pressure in the
man mentioned in Concept Check 11.
13. Why is it more efficient to put ACE in the pulmonary vasculature than in the systemic
vasculature?
14. Incorporate the thirst reflex into Figure 20.8.
15. Map the pathway that begins with renal artery stenosis and ends with hypertension.
(Hint: It involves the RAAS pathway.)
16. In equation 6, the amount of HCO3- present is increased at equilibrium. Why doesn’t
this HCO3- act as a buffer and prevent acidosis from occurring?
17. Why is ATP required for H+ secretion by the H+-K+ transporter but not for the Na+-H+
exchanger?
18. In hypokalemia, the intercalated cells of the distal nephron reabsorb K+ from the
tubule lumen. What happens to blood pH as a result?
Concept Check Chapter 20 Answers:
1. More water pores when vasopressin is present.
2. If vasopressin action is suppressed, the urine is dilute.
