The resting membrane potential depends mainly on gradient of
Ans. b (Potassium). (Ref. Ganong Physiology, 21st ed., 55, 56)Myocardial action potentialPhase 0Rapid upstrokeVoltage-gated Na-channels open.Phase 1Initial repolarizationInactivation of voltage-gated Na+ balances K+ effiux.Phase 2PlateauCa2+ influx through voltage-gated Ca2+ channels balances K+ efflux.Ca2+ influx triggers myocyte contraction.Phase 3Rapid repolarizationMassive K+ efflux due to opening of voltage gated slow K+ channels and closure of voltage-gated Ca2+ channelsPhase 4Resting potentialHigh K+ permeability through K+ channels
Sodium
Potassium
Chloride
Calcium
General