Muster: K+/Ca++ Homeostasis Flashcards
What 2 primary functions does potassium serve?
- Cell metabolism
2. The ratio of intracellular/extracellular potassium is the primary determinant of the resting potential of cells
What’s the concentration of K+ inside the cells?
140-150 mM
What is the extracellular concentration of Na+?
140 mM
What % of Potassium is stored intracellularly?
98 %
What factors stimulate the Na/K ATPase?
Insulin
Catecholamines
What other factors impact shift control?
Plasma K+ (cellular uptake may be increased when serum K rises)
Exercise (muscle cells release K+)
Cell breakdown
Chronic Disease (ex. metabolic acidosis: H+ in cells, K+ gets kicked out)–you have to be very acidotic before this causes hyperkalemia
Through what receptors do catecholamines stimulate the Na/K ATPase?
B-2
The proximal tubule reabsorbs what percent of K+ and Ca++?
Thick ascending limb?
Intercalated cell?
55-65 % proximal tubule
25 % Thick ascending
10 % Intercalated Cells? (late distal tubule and collecting duct)
What do Aldosterone and Angiotensin II do to ROMK?
Aldosterone: increases ROMK going from vessel to membrane
Angiotensin II: Blocks ROMK
What blocks ROMK on the intracellular side?
Mg2+
When is the BK channel opened?
In high potassium states (so then we ultimately have 2 channels facilitating the excretion of K+; ROMK and BK)
In a low potassium diet, there is no activity of ______ channel.
BK channel
In a low potassium diet, there is decreased presence of _________channel because there is a decrease in ____________.
ROMK
Aldosterone
What two things increase Aldosterone?
Angiotensin II
K+
What is the goal of PTH?
Increase serum Ca++
