What is the primary pacemaker of the heart responsible for setting the heart rate?

The sinoatrial node, known as the SA node, serves as the primary pacemaker of the heart. It is located in the right atrium and is responsible for generating electrical impulses that initiate the heartbeat and set the rhythm of the heart. The SA node automatically discharges electrical signals at regular intervals, typically around 60 to 100 times per minute in a healthy adult, which determines the heart rate.

When the SA node fires, it causes the atria to contract and pump blood into the ventricles. This intrinsic ability to generate action potentials makes the SA node the primary driver of the heart's rhythm. Other components of the cardiac conduction system, such as the atrioventricular node, bundle of His, and Purkinje fibers, play important roles in conducting the electrical signals through the heart but do not initiate the signals necessary to determine the heart rate. Instead, these structures act as conduits that facilitate the transmission of impulses from the SA node throughout the heart.