The primary pacemaker, known as the sinoatrial (SA) node, is a cluster of cells located in the right atrium that initiates the electrical impulses regulating heart rhythm. Its proper function is crucial for maintaining a consistent heart rate and ensuring effective blood circulation. Dysfunction of the SA node can lead to arrhythmias, such as bradycardia or atrial fibrillation, which may require medical intervention, including pacing or medication.