Ventricular action potential

As sodium channels close calcium provides current to maintain the potential around 20 mV.

The plateau lasts on the order of 100 ms. At the time that calcium channels are getting activated, channels that mediate the transient outward potassium current open as well.

This outward potassium current causes a small dip in membrane potential shortly after depolarization.

Fast delayed rectifier channels open quickly but are shut by inactivation at high membrane potentials.

As the membrane voltage begins to drop the channels recover from inactivation and carry current.