What is considered the primary pacemaker of the heart?

The primary pacemaker of the heart is the SA node, or sinoatrial node. Located in the right atrium, the SA node generates electrical impulses that initiate each heartbeat, thus setting the pace for the entire heart. This node is particularly crucial because it regulates the heart rate and ensures that the heart beats in a coordinated and efficient manner.

The SA node discharges impulses at a rate of about 60 to 100 beats per minute under normal physiological conditions, which is why it is considered the dominant pacemaker. The impulses it generates spread through the atria, leading to atrial contraction, and eventually reach the AV node, where they are briefly delayed before traveling through the bundle of His and the Purkinje fibers, resulting in ventricular contraction.

In the hierarchy of cardiac electrical activity, while other components like the AV node, Purkinje fibers, and Bundle of His have their roles in conducting impulses, they typically act as backup pacemakers. If the SA node fails, these structures may take over the pacing function, albeit at a slower rate, which underscores the SA node's role as the primary and most influential pacemaker in maintaining normal heart rhythm.