What structure in the heart is known as the heart's "pacemaker"?

The sinoatrial (SA) node is referred to as the heart's "pacemaker" because it is responsible for initiating the electrical impulses that dictate the heart's rhythm. Located in the right atrium, the SA node generates spontaneous electrical signals that cause the atria to contract and pump blood into the ventricles. This action sets the pace for the heart rate under normal physiological conditions.

The intrinsic rate of the SA node is typically between 60 and 100 beats per minute in a resting adult, which is how it determines the overall heart rate. The signals produced by the SA node then propagate through the heart's conduction system, including the atrioventricular (AV) node and the Purkinje fibers, leading to a coordinated heartbeat.

While the AV node, Purkinje fibers, and other structures contribute to the heart's electrical conduction system, they serve different roles. The AV node acts as a gatekeeper, delaying the electrical impulse before it moves to the ventricles, allowing for complete atrial contraction. Purkinje fibers distribute the impulses throughout the ventricles to ensure they contract simultaneously. The coronary sinus is not involved in the regulation of heart rhythm but instead is responsible for draining blood from the heart muscle back into the