Final answer:
Cardiac action potentials originate in pacemaker cells found at the SA node, and are then conducted through the heart's conduction system including the Purkinje fibers, leading to coordinated contractions of the heart muscle.
Step-by-step explanation:
Cardiac action potentials usually originate in pacemaker cells. These cells are self-excitable and have the unique ability to depolarize to threshold and fire action potentials on their own, which is known as autorhythmicity. This capability sets the heart rate. Pacemaker cells are found at the sinoatrial (SA) node, which is located near the wall of the right atrium. The depolarization spreads through the heart's conduction system, namely the atrioventricular (AV) node, the bundle of His, bundle branches, and finally, the Purkinje fibers. The Purkinje fibers are fast-conducting and spread the impulse to the myocardial contractile cells in the ventricles, promoting a coordinated contraction of the heart muscle.
Cardiac action potentials are predominantly initiated by pacemaker cells, distinctive for their self-excitable nature and the ability to spontaneously depolarize to threshold, generating action potentials independently—this phenomenon is termed autorhythmicity. The primary location of pacemaker cells is the sinoatrial (SA) node, situated near the right atrium's wall. The spontaneous depolarization triggers action potentials that propagate through the heart's conduction system: the atrioventricular (AV) node, bundle of His, bundle branches, and ultimately, the Purkinje fibers. The Purkinje fibers exhibit rapid conduction, efficiently transmitting the impulse to the myocardial contractile cells in the ventricles. This orchestrated propagation ensures a synchronized and coordinated contraction of the heart muscle, establishing the heart rate. The inherent autorhythmicity of pacemaker cells, coupled with the specialized conduction system, is fundamental to the rhythmic and efficient pumping action of the heart.