The Sinoatrial Node, often referred to as the SA node, is a small cluster of cells located in the right atrium of the heart. It serves as the primary pacemaker, generating electrical impulses that initiate each heartbeat. This natural pacing helps regulate the heart's rhythm and ensures that blood is pumped efficiently throughout the body. The SA node is influenced by the autonomic nervous system, which can adjust the heart rate based on the body's needs. For example, during exercise, the sympathetic nervous system increases the heart rate, while the parasympathetic system slows it down during rest.