L16-Potassium regulation

Question 1

Where is the majority of potassium in the body?

Answer 1

Stored intracellularly

Question 2

What are the volumes of intracellular and extracellular spaces?

Answer 2

Intracellular 14L

Extracellular 28L

Question 3

What equation represents the ions when at electrical equilibrium?

Answer 3

[K+in]/[K+out] is constant
The potassium inside the cell over the potassium outside the cell is constant. When more potassium is added extracellularly its distribution can be calculated using this equation.

Question 4

What are the clinical problems of hyperkalaemia and hypokalaemia?

Answer 4

Dysrhythmias

Question 5

How is K+ reabsorbed throughout the nephron?

Answer 5

Reabsorbed passively through the proximal tubule, paracellularly.
Reabsorbed in the thick ascending limb by the NKCC cotransporter however much of K+ cycles back into the filtrate
Distal tubule and collecting duct through the principle cells:
-Apical membrane K+ channel (ROMK), under the control of aldosterone.
A Ca2+-activated K+ channel (flow rate dependent)

Question 6

How does EPO work?

Answer 6

Binds to the erythropietin receptor in the bone marrow which increases the production of proerythroblasts. Also acts as an anti-apoptoic agent for erythrocytic progenitors.

Question 7

What form is vitamin D converted to when it enters the body?

Answer 7

Converted to 1,25-dihydroxycholecalciferol in the kidney under the control of PTH and calcitonin

Question 8

What action does Vitamin D have?

Answer 8

Increases Ca2+ and phosphate absorption and decreases their excretion.