Tubular function 5 Flashcards
What detects a change in osmolality in ECF?
Hypothalamic osmoceceptors
What are the 2 main responses to a rise in osmolality?
ADH secretion
Thirst mechanism
Where are most potassium ions reabsorbed?
Which cell in the LDT and CD secrete potassium ions into the lumen?
Proximal tubule
Principal cells secrete K+ ions in LDT and CD to the lumen
In PCT, what is the main route of K+ reabsorption?
paracellular reabsorption
How is K+ reabsorbed in:
Loop of Henle?
LDT?
Intercalated cells?
Loop of henle - symporter protein
LDT - potassium channels
intercalated cells - hydrogen exchanger
What are the 2 major determinants of K+ secretion?
Tubular secretion of K+ in principle cells (or plasma conc. K+)
Aldosterone
How does aldosterone promote K+ secretion? 3 ways
Increases Na+ reabsorption
Increases Na+/K+ ATPase activity = increase cell K+
Increases luminal K+ permeability
How does increased plasma [K+] promote K+ secretion? 3 ways
- Increases luminal K+ permeability
- Increases Na+/K+ ATPase activity
- Stimulates secretion of aldosterone
On which protein channel do K+ sparing diuretics work on?
Block sodium intake channels, which slows down loss of potassium
What are 3 other factors affecting renal secretion of K+?
Distal flow rate - keeps luminal K low and allows K secretion
Na+ reabsorption
Acid-base balance
How is K+ linked to acid-base balance?
Acidosis?
Alkalosis?
acidosis = hyperkalemia (dec sodium pump, apical membrane permeability to K and inc H+K+ATPase) alkalosis = hypokalemia
What are 3 effects of acidosis on K+ secretion ?
increased H+, which inhibits sodium pump, and drops apical membrane permeability to K+, and increases activity of H+/K_ ATPase
How can diuretics affect K+ secretion?
Increases distal flow rate = increases K+ secretion
For Na+ reabsorption, what’s one ion that doesn’t move which is crucial for K+ reabsorption? Why?
Cl-
