Berne and Levy Ch. 33 Solute and Water Transport along the Nephron: Tubular Function

Question 1

Where are 2/3 of water, Na+, Cl-, K+, and other solutes reabsorbed?

Answer 1

Proximal tubule

Question 2

Where are glucose and amino acids reabsorbed?

Answer 2

Proximal tubule

Question 3

What mediates this massive reabsorption at the proximal tubule?

Answer 3

Na, K-ATPase

Question 4

How does Na+ transport change from the first part of the PT to the second part?

Answer 4

1) reabsorbed with HCO3 (antiporter) and other organic molecules (symporter) such as glucose and amino acids
2) reabsorbed with Cl-

Question 5

As many organic molecules and lots of Na+ are reabsorbed at the beginning of the PT, what happens to the osmolality of the interstitial fluid compared to the osmolality of the tubule fluid?

Answer 5

Interstitial osmolality INCREASES causing water to passively flow out of tubule into interstitium (this concentrates Cl- and allows Na+ transport to move with Cl- in the second half of the PT)

Question 6

Why does Na+ move with Cl-?

Answer 6

Cl- moves down its gradient out of the tubule but that changes the charge of the cell (makes it more ++++) so Na+ follows it out.

Question 7

What drives the reabsorption of 2/3 of the water at the PT?

Answer 7

the transtubular osmotic gradient that is created by solute reabsorption)

Question 8

True or false, the PT is isosmotic (little to no difference in osmolality of tubular fluid at start and end of PT)

Answer 8

True

Question 9

What is solvent drag and what solutes are subject to it?

Answer 9

movement of solutes along with carriers (like Na+) - K+ and Ca++ are subject to it

Question 10

The loop of Henle reabsorbs ____ of filtered NaCl and __ of filtered water

Answer 10

25%; 15%

Question 11

The ___________ is permeable to water while the ____________ is not

Answer 11

descending thin limb; ascending limb

Question 12

Where in the loop of Henle is NaCl reabsorbed?

Answer 12

ascending thick limb

Question 13

What is the charge of the tubular fluid at the thick ascending limb?

Answer 13

POSITIVE

important for driving force to reabsorb cations such as Na, K, Mg, Ca

Question 14

What part of the nephron is known as the “diluting segment?”

Answer 14

Thick ascending limb (reabsorbs NaCl reducing the osmolality of tubular fluid)

Question 15

Function of principal cells

Answer 15

reabsorb NaCl and water

secrete K+

Question 16

Function of intercalated cells

Answer 16

secrete H+ or HCO3 (regulate acid-base)

reabsorb K+