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10 Cards in this Set
- Front
- Back
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[Ca] & [Pi] in ECF |
Near precipitation lvls -> need to be regulated In ICF -> 10,000x lower Plasma [Ca] ~ 2.5 mM Cyto [Ca] ~ 100 nM |
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Effects of hypocalcemia & hypercalcemia |
hypocalcemia - decreasing threshold potential in MN's (tetany, bronchospasm) - SM: vasodilation, ↓BP - arrhythmias - demineralization of bones hypercalcemia - opposite; kidney stones |
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Renal handling of Ca |
UF of non protein-bound of Ca & reabsorption (95-99%) 70%: PT (parallel to Na) 20%: TAL Rest: DT, CD - active => regulated: Ca channel (luminal) -> Ca-ATPase, Na/Ca exchanger (basolateral) (intracellular Calbindin) => opposite to Na |
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Ca vs. A-B balance |
↑ pH => binding of Ca to albumin (instead of H+) Acute hyperventilation -> ↑ pH -> plasma [Ca] drops Acidic pH -> ↓ Ca reabsorption in kidney, bone demineralization |
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Pi vs. A-B balance |
Alkalosis (especially respiratory) => ECF -> ICF [via PFK activation] |
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Renal handling of Pi |
85% reabsorbed in PT (parallel to Na) Also main site of regulation |
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Regulation of Ca & Pi |
↓ [Ca] => PTH (CaSR) => - ↑ Ca & Pi release from bone - ↑ Ca reabsorption in DT - ↓ Pi reabsorption in PT (lowering Tm) - vit D3 -> active form => Ca absorption |
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Mg defficiency |
- ↑ K channel open prob -> K depletion - ↑ ICF [Ca] -> ↑ vascular resistance in SM |
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Renal handling of Mg |
Paracellular reabsorption PT: 15%LoH: 75% Transcellular, regulated: DT: 1-10% Regulated by plasma [Mg] |
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Mechanisms protecting against Nephrocalcinosis & kidney stone formation |
- Sites of reabsorption & regulation (Ca, Pi, Mg) are different - Monitoring Ca reabsorption w/ CaSR's -- on BL membrane of TALH => ↓ Ca & Mg reabsorption -- on L membrane of CD => ↓ ADH-dependent H2O reabsorption -> preventing concentration of urine => ↑ H+ secretion - incomplete reabsorption of citrate (Ca & Mg chelator) |
