The action potential of the the sinoatrial node
The action potential of the sinoatrial node and atrio­ventricular node results from the opening of the slow Ca2+ channels and the influx of Ca2+(some Na+ may also enter through these slow Ca2+channels). An action potential is elicited when the membrane potential reaches threshold. Spontaneous depolarization is an intrinsic property of nodal tissue and can occur in the absence of nerves. The low resting potential results in a small action potential that propagates slowly. The rapid Na+ channels are inactivated in nodal tissue. An increase in the conductance to K+ would hyperpolarize the membrane.
Reuslts from the activation of rapid Na+ channels
Results from opening of the slow Ca2+ channels
Is equivalent in height and conduction velocity to that of the atrial muscle
Results from an increase in conductance to K+