Potassium Control Flashcards
Where is most the potassium in the body stored?
98% in ICF
Why is maintain ECF [K+] critical?
Its effect on resting membrane potential
Its effects on the excitability of cardiac tissue
How is ECF K+ regulated?
Internal balance - immediate control
External balance - longer term
What happens to potassium after a meal?
Absorbed by intestine and colon
Goes into blood
Moves into cells immediately
Kidneys excrete it in 6-12 hours
What is internal balance?
Movement of potassium between ECF and ICF
What makes up internal balance?
Movement of K+ from ECF into cells
- Na-K-ATPase
Movement of K+ out of cells into ECF
- K+ channels
What factors increase K+ uptake by cells?
Hormones
- insulin
- aldosterone
- catecholamines
Increased ECF [K+]
Alkalosis
What factors promote K+ shift out of cells?
Exercise Cell lysis Increase in ECF osmolality Low ECF [K+] Acidosis
What is the effect of insulin on potassium movement?
Increases Na-K-ATPase activity - increases k+ uptake
What is the effect of aldosterone on potassium movement?
Increases Na-K-ATPase activity - increases k+ uptake
What is the effect of catecholamines on potassium movement?
Increases Na-K-ATPase activity - increases k+ uptake
What is the effect of exercise on potassium?
Exercise increases [K+]
- release of k+ during recovery phase of AP
- muscle damage releases K+
Non-contracting tissues - uptake K+
Exercise releases catecholamines - increases K+ intake by cells
What is external balance?
Excretion of K+
Where is potassium reabsorbed in the kidney?
PCT
Thick ascending limb of LOH
DCT
CD - intercalated cells
Where is potassium secreted in the kidney?
DCT
Cortical collecting duct - principal cells
