What initiates the electrical impulses that regulate the heart's rhythm?

The SA node, or sinoatrial node, is the natural pacemaker of the heart, responsible for initiating electrical impulses that regulate the heart's rhythm. Located in the right atrium, it generates electrical signals that cause the heart muscle to contract and pump blood. These impulses dictate the heart rate and synchronize the contractions of the atria and ventricles.

The SA node sets the pace of the heartbeat, typically at a rate of 60 to 100 beats per minute under normal physiological conditions. It also plays a crucial role in ensuring the heart functions effectively as a coordinated unit, adapting to the body's varying demands for blood flow during different activities.

While other components of the electrical conduction system, such as the AV node, the Bundle of His, and the Purkinje fibers, are important in conducting and relaying these impulses, they do not initiate the rhythm themselves. Instead, they respond to the signals generated by the SA node to coordinate further contractions of the heart. Therefore, the SA node’s function is foundational to the overall electrical activity and rhythm of the heart.