Repolarization of the cardiac action potential results in what?

• A. Depolarization to a Higher Potential
• B. Return of the Membrane to Resting Potential
• C. Plateau Phase Due to Calcium Influx
• D. Initiation of Action Potential

Answer: (B)

Repolarization is the phase where the cardiac cell’s membrane potential moves back toward its negative resting level after it has depolarized. In ventricular myocytes this happens as outward potassium currents increase and calcium entry declines: potassium channels open, calcium channels close, and the membrane potential shifts from the plateau/positive range back down toward the resting value, which is about -85 to -90 mV. The cell then remains at this resting potential until the next impulse, thanks in part to the Na+/K+ ATPase helping restore and maintain the ionic gradients. So repolarization results in the return of the membrane to resting potential. It’s not the depolarization to a higher potential, nor the plateau phase, nor the initiation of an action potential.