Lecture 20: Renal Regulation of Ion Concentrations Flashcards
What happens when there is higher concentrations of extracellular potassium?
cardiac arrest or fibrillation
What is the normal intracellular concentration of potassium ion?
140 mEQ/L
What are the major factors responsible for potassium excretion?
direct influence on distal renal tubules and collecting ducts via increase in extracellular potassium ion concentrations
effects of aldosterone secretion on potassium excretion: increase in extracellular potassium stimulates increase in aldosterone secretion
Where does reabsorption occur?
proximal tubule
ascending limb of henle
Where does secretion occur?
late tubule
collecting duct
mechanisms of potassium secretion and sodium reabsorption and secretion by ____
principal cells
high sodium diet leads to little change in _____
potassium excretion
What is acidosis?
less calcium is bound to the plasma proteins
What is alkalosis?
More calcium is bound to the plasma protein
Where is almost all of calcium stored?
bone
What are PTH effects?
stimulates bone reabsorption
stimulates activation of vitamin D
indirectly increases tubular calcium reabsorption
_____ percent of filtered calcium is reabsorbed
99
Reabsorption in loop of henle is restricted to the _____
thick ascending limb
calcium reabsorption in distal tubule is almost entirely _____ transport
active
What decreases calcium excretion?
increase levels of PTH
increase levels of concentration of phosphate
increase metabolic alkalosis
What is phosphate excretion controlled by?
overflow mechanism
PTH promotes bone excretion, which ____ phosphate in extracellular fluid
increases
If PTH decrease transport maximum for phosphate by renal tubules, then there is a greater _______ of phosphate in urine
loss
What does insulin do?
stimulates potassium uptake by cells
What is hypokalemia?
excess secretion of aldosterone (Conn’s syndrome)
What is hyperkalemia?
deficiency in aldosterone secretion (Addison’s disease)
What does aldosterone do?
increases potassium uptake by cells
stimulates active reabsorption of Na+ by principal cells via Na+K+ATPase
increases permeability of luminal membrane for K+
increases extracellular K+
What do catecholamines do?
Beta adrenergic stimulation
Metabolic acidosis ______ extracellular K+
increases
Metabolic alkalosis _____ extracellular K+
decreases
What is the normal rate of potassium filtration?
180 L/day
Rate is the rate of potassium reabsorption in the proximal tubule and loop of henle
65% proximal tubule
25-30% loop of henle
Where are principal cells found?
late distal tubule and cortical collecting tubules
What factors stimulate K+ secretion?
increase in:
extraceullar fluid K+ concentration
aldosterone
tubular flow rate
What do intercalated cells do?
reabsorb K+ during K+ depletion
