PHGY 312 Lecture Notes - Lecture 11: Ventricular Fibrillation, Kidney Failure, Romk
24 May 2016
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Phgy 312-lecture 11: potassium homeostasis and renal excretion of potassium. Fluctuations in dietary k+, need constant [k] in cells and ecf. Body needs to regulate [k] in ecf and adjust k excretion. Significant shifts in k conc in the plasma can lead to hyperkalemia/hypokalemia. Hypokalemia = <3meq in ecf: cause: diuretics, vomiting, diarrhea (loss of k not recovered by kidney, leads to ventricular fibrillation, arrhythmia. Hyperkalemia = >5meq in ecf: cause: renal failure, acei, hyperglycemia, leads to depression of membrane potential. 5-10% of k lost in feces and sweat. 67% reabsorbed at pt, 20% in loop of henle (no secretion takes place here: regardless of condition (k depletion/normal/increased k), 87% is reabsorbed at pt/henle, only the amount of reabsorption/secretion at the dt changes! Secretion of k is regulated by principal cells. Occurs via activity of na/k atpase, kcc1 (k/cl symporter), and romk & bk (k channels: creates driving force for k movement across apical membrane.
