Physiology of the Heartbeat

Abstract

The spontaneous, rhythmic generation of APs in the intrinsic pacemaker centers of the heart is the basis of the autonomous heartbeat rhythm [6]. Normally, the heartbeat is initiated in the SA node. The AP generated propagates from one muscle cell to the next until it has spread over the entire atrial wall and reached the AV node at the boundary between the atrium and the ventricle. Because of the low conduction velocity in the AV node, there is a delay in transmission of the wave of excitation to the ventricles that allows the atrial contraction to be completed before contraction of the ventricles begins (Figure 10). From the AV node, the excitation passes along the His bundle through the atrioventricular boundary.