Loop of Henle, Distal Tubule, Collecting Duct

Question 1

% of filtered Na reabsorbed in the Loop of Henle?

Answer 1

25%

Question 2

Descending loop is permeable only to:

Answer 2

Water (reabsorbed)

Question 3

Osmolality of filtrate as it passes through descending, deep medullary, and ascending loop:

Answer 3

300 mOsms

1400 mOsm

100 mOsm

Question 4

Which segment of loop is not permeable to water?

Answer 4

Ascending

Question 5

Membrane apparatus carrying solutes from collecting tubule lumen into cell in the Thick Ascending Limb?

Answer 5

NKCC pump

Question 6

What is the driving force of the NKCC pump?

Answer 6

Na

Question 7

What is the limiting factor in the NKCC pump?

Answer 7

Cl

Question 8

% of the filtered Na reabsorbed in the Thick Ascending Loop?

Answer 8

20%

Question 9

Type of diuretic that acts on NKCC pump?

Answer 9

lasix (furosemide)

Question 10

% of filtered Na reabsorbed in the Distal Tubule?

Answer 10

5%

Question 11

Is distal tuble permeable to water?

Answer 11

no

Question 12

Pump of action in the distal tubule?

Answer 12

Na/Cl symporter….secondary active transport driven by Na

Question 13

Genetic mutation of NaCl pump in distal tubule?

Answer 13

Gitleman Syndrome

Question 14

5 key features of Gitleman Syndrome:

Answer 14

1. Normal BP
2. Metabolic alkalosis
3. hypocalciuria
4. hypomagnesemia
5. hypokalemia

Question 15

Drugs that manipulate NaCl channel in distal tubule?

Answer 15

thiazide diuretics

Question 16

First area with VARIABLE reabsorption of Na?

Answer 16

Collecting duct

0-5%

Question 17

Two principle channel types in Principal cells of collecting tubules?

Answer 17

ENac’s (epithelial Na channels)

ROMK’s (renal outer medullary K channels)

Question 18

Collecting duct permeability to water?

Answer 18

Variable

Question 19

Primary mechanism of controlling salt reabsorption in principle cells?

Answer 19

Aldosterone

**regulated by RAAS

Question 20

3 primary signals stimulating renin release?

Answer 20

1. SNS–NE
2. Decreased stretch in afferent arterioles
3. Decreased Cl delivery to macula densa

Question 21

Where is renin released from?

Answer 21

Juxtaglomerular cells in the afferent arteriole

Question 22

Clinical triggers for renin release:

Answer 22

1. hypovolemia
2. low Na diet
3. low body NaCl
4. high SNS activity

Question 23

4 primary actions of Angiotensin II:

Answer 23

1. stimulates aldosterone
2. systemic vasoconstriction
3. stimulates proximal tubule reabsorption of Na
4. Increases SNS activity

Question 24

Why can aldosterone cross freely into cells?

Answer 24

lipophilic

Question 25

What cell does aldosterone act on and what does it do there?

Answer 25

Principal cells of the collecting duct

-increases transcription of ENaCs, ROMKs, and Na-K-ATPase (basolateral membrane)

Question 26

What does ROMK do?

Answer 26

Secretes K into collecting duct

Question 27

% of filtered Na controlled by aldosterone:

Answer 27

2%

Question 28

Little’s syndrome?

Answer 28

can’t shut off ENaCs –> increases BP

Question 29

Type I pseudohypoaldosteronism?

Answer 29

loss of ENaC function