sodium reabsorption

Question 1

What determines the volume of the extracellular water compartment?

Answer 1

sodium as it is predominant cation in the ECF

Question 2

Most of the Na reabsorption occurs in the early PCT. Two things make this possible, what are they?

Answer 2

Na/H exchange, powered by the Na/K ATPase pump and Na/glucose exchange, also powered by Na/K pump

Question 3

In the late PCT, _______% of Na reabsorption is by passive transport

Answer 3

50% (The rest is Na/K pump)

Question 4

Water in the ___________ is reabsorbed in a way that is isosmotic

Answer 4

proximal tubule

Question 5

True or False, Increased GRF (and FF) will alter the amount of sodium absorbed or secreted.

Answer 5

False! Increased filtration will result in increased oncotic pressure in the capillaries which will also increase sodium reabsorption proportionately (via solvent drag) to maintain constant 67% reabsorption.

Also, Increased GFR also means increased load of glucose and AA’s are filtered, their reabsorption is couples with sodium. They will all be reabsorbed proportionally

Question 6

What osmotically active agents are related to sodium reabsorption?

Answer 6

glucose and AA’s

Question 7

What hormonal factors stimulate sodium/water reabsorption at the pct?

Answer 7

AT2 and sympathetic NT’s

Question 8

What hormonal factors inhibit sodium/water reabsorption at the pct?

Answer 8

NO and BNP

Question 9

What diuretics target the PCT? What complications will this involve?

Answer 9

Na/K ATPas inhibitors, carbonic anhydrase inhibitors (Diamox), osmotic diuretics (mannitol)

Potassium depletion

Question 10

What is being filtered/absorbed in the PCT?

Answer 10

sodium is filtered!

Question 11

What is being filtered/absorbed in the thin descending limb?

Answer 11

No sodium!!! H2O is being passively reabsorbed

Question 12

What is being filtered/absorbed in the thin ascending limb?

Answer 12

Passive reabsorption of NaCl. NO water!!!

Question 13

What is being filtered/absorbed in the thick ascending limb?

Answer 13

50/50 passive and active reabsorption of NaCl accounts for 25% of total Na reabsorption. NO water!!

Question 14

In addition to AT2 and SNS, what other hormonal factors affect Na reabsorption in the thick ascending limb?

Answer 14

aldosterone and ADH

Question 15

What is the active transport mediator in the thick ascending limb?

Answer 15

Na/K/Cl symporter

Question 16

________ diuretics inhibit the Na/K/Cl symporter

Answer 16

loop

Question 17

What is happening with loop diuretics, how do they work?

Answer 17

the Na/K/Cl symporter is responsible for 50% of the 25% of Na reabsorption taking place in the nephron. So without this symporter there is about 12.5% more osmotically active Na in the nephron which pulls in a bunch of water to be wasted in the urine.

Question 18

What else is reabsorbed by Na/K/Cl symporter that will be lost in the urine if not reabsorbed?

Answer 18

K

Question 19

what is the potassium sparing diuretic? and How does it work

Answer 19

spironolactone, it binds to the mineralocorticoid receptor that typically receives aldosterone

Question 20

What does aldosterone actually do to increase fluid retention?

Answer 20

Increases the number of Na/K ATPase pumps and increases the number of Na/Cl symporters