1
Currents caused by opening of which of the following channels contribute to the repolarization phase of the action potential
of ventricular muscle fibers?
EXPLANATION
Intercellular Communication, Ion Channels & S
- Ionic Basis of Cardiac Ventricular Repolarization: In cardiac ventricular myocytes, the rapid final repolarization phase (Phase 3) of the action potential is driven by the opening of voltage-gated $K^+$ channels.
- Potassium Efflux Currents: Inward-rectifier potassium current ($I_{K1}$) and delayed-rectifier potassium currents ($I_{Kr}$ and $I_{Ks}$) cause massive outward $K^+$ efflux, restoring the negative resting membrane potential ($\approx -90\text{ mV}$) as voltage-dependent L-type $Ca^{2+}$ channels close.
Correct option: (4) K* channels
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