Final answer:
The sinoatrial (SA) node is the pacemaker of the heart, which initiates the normal heart rhythm by the highest inherent rate of depolarization. The AV node further regulates the timing of the pulse transmission to the ventricles, allowing proper coordination of atria and ventricles contraction.
Step-by-step explanation:
The pacemaker of the heart among vertebrates is the sinoatrial (SA) node. This specialized clump of myocardial conducting cells is located in the superior and posterior walls of the right atrium, near the orifice of the superior vena cava. The SA node has the highest inherent rate of depolarization and initiates the sinus rhythm, which is the normal electrical pattern for the contraction of the heart. An important aspect of the heart's electrical system is the Atrioventricular (AV) node, situated in the inferior portion of the right atrium within the atrioventricular septum. This node is responsible for a critical pause before the impulse is transmitted to the ventricles, ensuring the atria have time to empty into the ventricles before they contract.
The cardiac conduction system includes the sinoatrial node, internodal pathways, the AV node, the bundle of His, right and left bundle branches, and the Purkinje fibers, all of which coordinate the heart's rhythmic contractions.