Final answer:
The pacemaker of the heart is the sinoatrial (SA) node, responsible for initiating the sinus rhythm and regulating cardiac beating.
Step-by-step explanation:
The pacemaker of the heart is known as the sinoatrial (SA) node, which is a specialized clump of myocardial conducting cells positioned in the superior and posterior walls of the right atrium near the entrance of the superior vena cava. The SA node has the highest inherent rate of depolarization within the heart's conduction system, and it is responsible for initiating the sinus rhythm, thus regulating the normal cardiac rhythm. Its inherent pace of depolarization establishes it as the primary pacemaker of the heart. This is how the heart's autonomous beating is regulated, allowing for properly timed contractions. Electrical impulses originate from the SA node, causing the atria to contract, then reach the atrioventricular (AV) node, pause briefly, and subsequently travel through the bundle of His, bundle branches, and ultimately to the Purkinje fibers, culminating in the contraction of the ventricles.