PRACTICE QUESTIONS

1. Which segment of the renal tubule is responsible for the reabsorption of the bulk of filtered solutes?

a. Proximal tubule

b. Thin limbs of Henle’s loop

c. Thick ascending limb of Henles loop

d.

e. Collecting duct

2. The main driving force for the reabsorption of solutes from the tubule fluid is:

a. Active transport of solutes across the apical plasma membrane

b. Secondary active transport of solutes across the apical plasma membrane

c. Active transport of Na⁴ from the tubule epithelial cell across the basolatcral plasma membrane by the electrogenic Na’ channel

d. Active transport of Na* from the tubule epithelial cell across the basolatcral plasma membrane by the Na⁺,K⁺-ATPase pump

e. Passive diffusion of solutes through the paracellular pathway

3. The net rate of reabsorption of a solute in the proximal tubule fluid is determined by the:

a. Rate of active transport of the solute

b. Rates of tubular reabsorption and secretion of the solute

c. Systemic requirements of the animal for the solute

d. Lipid permeability of the solute

e. Glomerular filtration rate

4. The ultimate rate of excretion of K* in the urine is determined by the:

a. Concentration of K⁺ in the glomerular filtrate.

b. Proximal tubule, which reabsorbs or secretes K* to meet the physiological requirements of the animals.

c. Thick ascending limb, where K⁺ secretion is enhanced by high plasma K’ concentrations.

d. Distal convoluted tubule, which has K⁺ pumps that are inserted in the apical or basolateral plasma mem­branes, depending on the need for reabsorption or secretion of K’.

e. Collecting duct, in which the principal cells are capable of K¹ secretion, and the intercalated cells are capable of K* reabsorption.

5. Which of the following are effects of aldosterone on Na⁺ transport in the connecting segment and collecting duct?

a. Enhances the permeability of Na⁺ channels in the apical plasma membrane, thereby enhancing Na⁺ and water reabsorption.

b. Stimulates Na⁺,K^f-ATPase activity in the basolateral plasma membrane, thereby enhancing Na⁺ and water reabsorption.

c. Reduces the Na^, permeability of the apical plasma membrane, thereby inhibiting Na⁺ and water reabsorption.

d. Reduces Na*,K'-ATPase activity in the basolateral plasma membrane, thereby inhibiting Na⁺ and water reabsorption.

e. Reduces the K^, permeability of the apical plasma membrane, thereby inhibiting K* reabsorption.