what leads channels to open during action potential
It is the opening and closing of ion channels that alters specific ion conductances in a manner that determines resting potentials and generates action potentials. For example, when an action potential is elicited in a cardiomyocyte, sodium channels transiently open and potassium channels close, which leads to depolarization. Shortly thereafter (within a few milliseconds), the sodium channels close and calcium channels open to maintain a depolarized state. This is followed by inactivation of the calcium channels and a reopening of the potassium channels, which leads to membrane repolarization.