Final answer:
The heart cells in the sinoatrial (SA) node have the fastest rate of action potential initiation, making it the primary pacemaker of the heart.
Step-by-step explanation:
The heart cells with the fastest rate of action potential initiation are localized in the sinoatrial (SA) node. The SA node functions as the heart's pacemaker and establishes the normal cardiac rhythm. It possesses the highest inherent rate of depolarization compared to other parts of the heart's conduction system.
When the SA node initiates an action potential, it spreads across the atria. After a brief pause at the atrioventricular (AV) node, the signal continues through the atrioventricular bundle (bundle of His), to the bundle branches, and finally the Purkinje fibers in the ventricular walls. Although the Purkinje fibers spread the impulse rapidly within the ventricles, they do not initiate the impulse with the fastest rate; that property is unique to the SA node.
The heart cells with the fastest rate of action potential initiation are localized in the SA node. The SA node, also known as the sinoatrial node, is located near the wall of the right atrium. It is responsible for initiating the electrical signals that cause the heart to beat. The SA node has the highest inherent rate of depolarization and is considered the pacemaker of the heart.