Repolarization occurs because multiple choice potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close. the extra efflux of potassium ions causes the membrane potential to become slightly more positive than the resting value. the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level. more sodium ions diffuse into the cell than potassium ions diffuse out of it. the inactivation gates of the voltage-gated sodium ion channels begin to open and the diffusion of sodium ions decreases.