Myocardial action potential

Representation of a ventricular action potential. There are 5 phases of the action potential beginning with phase 0, rapid depolarization by sodium influx. Phase 1 is a rapid repolarization via potassium efflux followed by phase 2 or the plateau phase. The plateau phase results from entry of calcium into the cell and potassium efflux. Phase 3 repolarization is dominated by potassium currents which polarize the cell and potassium inward rectifier maintains the resting potential or phase 4. See text for full description.