Renal Sodium Balance

Question 1

What ion is most important in regulation of fluid content and body volume?

Answer 1

Sodium

Question 2

Which segments of the nephron absorb sodium?

Answer 2

All except descending loop of henle

Question 3

Which segment of the nephron filters to majority of sodium?

Answer 3

Proximal convoluted tubule - 65%

Question 4

How is sodium reabsorbed in the proximal convoluted tubule?

Answer 4

1. Co-transport with glucose, phosphate, amino acids
2. Counter transport against hydrogen
3. Diffusion
4. Paracellular

Question 5

What drives active transport of sodium in the proximal convoluted tubule?

Answer 5

Na/K ATPase on basolateral side

Question 6

What regulates Na reabsorption in the proximal convoluted tubule?

Answer 6

Flow (GFR) & angiotensin II

Question 7

How does angiotensin increase Na reabsorption

Answer 7

Increases activity of Na-H counter transporter

Question 8

How is sodium reabsorbed in the thick ascending limb of the loop of henle?

Answer 8

Na-K-2Cl (NKCC) co-transporter-active transport

K is recycled, Cl becomes the limiting ion

Question 9

How is sodium reabsorbed in the distal tubule?

Answer 9

Na-Cl co-transporter-active transport

Question 10

How is sodium reabsorbed in the collecting duct?

Answer 10

ENaC epithelial sodium channels in principal cells

Question 11

What are the effects of aldosterone in the collecting duct?

Answer 11

Increase sodium reabsorption by...
1. Increase activity of Na-K ATPase
2. Increase number of ENaC
3. Increase activity of ENaC
Increase secretion of K and H

Question 12

What are the effects of Atrial Natriuretic Peptide in the collecting duct?

Answer 12

Decrease Na reabsorption by …

1. Increasing GFR
2. Decrease activity of ENaC

Question 13

What regulates sodium reabsorption in the proximal tubule?

Answer 13

Flow & Angiotensin II

Question 14

What regulates sodium reabsorption in the ascending limb of the loop of henle?

Answer 14

Flow

Question 15

What regulates sodium reabsorption in the distal tubule?

Answer 15

Flow

Question 16

What regulates sodium reabsorption in the collecting duct?

Answer 16

Aldosterone & Atrial Natriuretic Peptide

Question 17

How is sodium regulated by osmolality and tonicity?

Answer 17

It is not

Question 18

What enzyme is responsible for converting angiotensin I to angiotensin II?

Answer 18

Angiotensin Converting Enzyme

Question 19

What enzyme is responsible for converting angiotensinogen to angiotensin?

Answer 19

Renin

Question 20

What are the consequences of increased angiotensin II?

Answer 20

1. Increased thirst
2. Increased vasopressin (ADH) release
3. Increased systemic vasoconstriction
4. Increased aldosterone release

Question 21

What happens when intravascular volume drops?

Answer 21

Increased production of angiotensin II (proximal convoluted tubule) & aldosterone (collecting duct)

Question 22

What hormones are released in response to intravascular volume increase due to dietary salt increase?

Answer 22

Atrial Natriuretic Peptide and Dopamine

Question 23

On what transporter do loop diuretics exert their effects?

Answer 23

NKCC in the loop of henle - loop diuretics compete for the Cl binding site

Question 24

Where do thiazide diuretics exert their effects?

Answer 24

Na-Cl co-transporter in the distal tubule

Question 25

How much sodium is absorbed in the proximal convoluted tubule?

Answer 25

65%

Question 26

How much sodium is absorbed in the ascending loop of henle?

Answer 26

25%

Question 27

How much sodium is absorbed in the distal tubule?

Answer 27

5%

Question 28

How much sodium is absorbed in the collecting duct?

Answer 28

5%

Question 29

How does amiloride (potassium sparing diuretic) exert its effects?

Answer 29

Blocks ENaC in the collecting ducts preventing Na influx into the principal cell