Potassium Balance and Renal Transport Flashcards Preview

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Flashcards in Potassium Balance and Renal Transport Deck (20):
0

Normal plasma [K+]?

4-5 mEq/L

1

Say you eat a bunch of K+, why does your plasma [K+] only increase a little?

Most of it rapidly moves into cells, renal excretion of K+ happens more slowly.

2

Can cells better buffer a K+ deficit or excess?

They can better buffer a deficit, as K+ can move out of cells, but they can't take up much extra.

3

If there weren't cellular uptake, eating 5ish bananas would be lethal.

Ok.

4

3 hormones that affect "internal" K+ balance?

Insulin
Catecholamines
Aldosterone

5

How do insulin, catecholamines, and aldosterone all affect plasma [K+]?

They decrease it by stimulating that Na+/K+ ATPase.

6

How do exercise and cell lysis affect ECF [K+]?

They increase it.

7

How does ECF hypertonicity affect ECF K+? How?
Example of when this happens?

ECF tonicity causes movement of water out of cells.
K+ follows the water via solvent drag.

This can happen with hyperglycemia in diabetics.

8

How can acidemia cause acute hyperkalemia?

High levels of H+ can bind to pumps/channels normally occupied by K+.

9

Acidemia -> hyperkalemia.
Alkalemia -> hypokalemia.

This makes sense... because high ECF H+ will displace some intracellular K+, and vice versa.

10

2 ways K+ is eliminated?

feces, urine

11

Where in the nephron is most K+ reabsorbed, at fixed rates?

80% in the proximal tubule.
Another 10% in thick ascending limb...

12

Where in the nephron is K+ excretion/reabsorption regulated?

After the thick ascending limb...

13

The 2 different cell types in the collecting duct have different effects on K+. Which does which?

Principal cells: K+ secretion.
Intercalated cells: K+ reabsorption.

14

How do alpha-intercalated cells reabsorb K+?

K+/H+ ATPase (moves K+ in, H+ out into lumen)

15

How do principal cells secrete K+?

K+/Cl- cotransporter moves it into lumen.

16

4 factors affecting distal tubule K+ secretion?

K+ intake, plasma [K+].
Aldosterone.
Distal tubule Na+ and flow.
Anions in tubular fluid.

17

How does flow through distal tubule affect how much K+ is secreted? Why?

More distal tubule flow, more K+ secretion for any level of intake.
More Na+ removed -> more K+ moved into lumen.

18

Why won't eating lots of Na+ make you hypokalemic?

Because aldosterone will be inhibited.

19

Why might sodium sulfate, if you gave it, cause hypokalemia?

Poorly absorbed anions will draw K+ into the tubule.
This applies to some drugs (and NaHCO3 at levels exceeding reabsorption capacities).