Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
10 Cards in this Set
- Front
- Back
Distribution of K in body |
>98% in cells Only 3.5-5 mM in ECF - low [K] -> vasoconstriction et vice versa Main determinant of cell V Required for cell fx's & growth Required for RMP |
|
Internal K balance |
Determined by Na/K-ATPase - EC K(M, K) ~ 1mM -> saturated - IC K(M, Na) ~ cell lvl -> IC [Na] affects [K]! |
|
Role of insulin in K balance |
-> ↑ K uptake: - ↑ Na/K-ATPase activity - ↑ glucose uptake -> G6P -> Na/Pi co-transport required -> - ↑ Na/H exchanger activity -> =>> ↑[Na](ic) -> Na/K-ATPase stimulated |
|
Role of exercise/catecholamines in K balance |
AP -> Na in, then K out -> ↑[Na](ic) -> N/Kase stimulated; BUT Na in < K out -> much more K lost than can be regained => K -> T tubules & circulation => catecholamines: - pre-exercise: epinephrine -> β-R -> ↑ N/Kase -> K uptake - post-exercise: norepinephrine -> α-R -> ↓ N/Kase -> K loss from muscle |
|
Role of A-B balance in K balance |
~ each H entering cell is replaced by K leaving -> electroneutrality - mostly during gain/loss of HCl (not organic acids / CO2) => K depletion -> IC acidosis, et vice versa |
|
Role of plasma osmolality in K balance |
Plasma hyperosmolality -> cell shrinkage -> ↑[K](ic) -> K leaks -> hyperkalemia - vice versa: hypotonicity, swelling (diabetes mellitus - glucose is effective osmolyte) |
|
External K balance |
Regulation of renal/GI K excretion K is present in most food -> K mostly excreted, not too necessary to conserve |
|
K transport along nephron |
PT: 2/3 K reabsorbed, passive paracellular Mediated by solvent drag & lumen + voltage (2nd half) ALH: thin - K secreted, passive (high medullary [K]) thick - most K reabsorbed again => cortico-papillary gradient -| back leak from CD in medulla DT & CD: cortical - principal cells (Na X K secretion) > α-type intercalated cells (H X K reabsorption) basal N/Kase: 3Na/2K -> Na reabsorbed > K secreted -> lumen '-' charge -> furhter luminal K channel secretion medullary CD - only reabsorption: passive & luminal H/Kase |
|
K secretion regulation |
Takes place predominantly in late DT & CCD ↑ Plasma [K] -> (↑ aldosterone) -> ↑ K secretion (directly) ↑ rate of Na reabsorption in CCD -> ↑ K secretion (coupled) ↑ [Cl-] (wrt/ other anios) in tubular fluid -> ↑ K reabsorption (w/ Cl-) ↑ Luminal flow rate -> ↑ K secretion (passive & signaling via cilia) ↑ ADH -> ↑ K secretion (water & K secretion uncoupled) ↑ pH -> K secretion |
|
TTKG (Trans-Tubular K Gradient) |
- Extrapolates driving F for K secretion by correcting for H2O reabsorption - Determines if inappropriate response to hyperkalemia is due to kidney fx TTKG = [U(K)/P(K)] / [U(osm)/P(osm)] |