Where are the normally dominant pacemaker cells of the heart found?

The normally dominant pacemaker cells of the heart are found in the sinoatrial node (SA node). The SA node is situated in the right atrium and is responsible for generating electrical impulses that initiate the heartbeat. This makes it the primary pacemaker of the heart, setting the rhythm and rate of each heartbeat under normal physiological conditions.

The SA node produces electrical signals that spread throughout the atria, causing them to contract and push blood into the ventricles. Its location and inherent automaticity allow it to take precedence over other potential pacemakers, like the atrioventricular node or the Bundle of His, which have slower intrinsic rhythms and act as secondary pacemakers only if the SA node fails to function properly.

Understanding the role of the SA node in establishing the heart's rhythm is crucial for recognizing how cardiac arrhythmias can develop when this natural pacemaker is disrupted.