Which heart structure is known as the primary pacemaker?

The primary pacemaker of the heart is the sinoatrial (SA) node. This structure is located in the right atrium and is responsible for initiating the electrical impulses that dictate the heart's rhythm. The SA node generates electrical signals at a rate of about 60 to 100 beats per minute under normal physiological conditions, establishing the baseline heart rate for the entire heart.

The signals produced by the SA node spread through the atria, prompting them to contract and pump blood into the ventricles. Following this, the electrical impulse travels to the atrioventricular (AV) node, which serves as a secondary pacemaker and can take over if the SA node fails, but it has a slower intrinsic firing rate. The Purkinje cells and the Bundle of His further conduct the impulse through the ventricles, allowing for coordinated contraction, but they do not set the primary rhythm of the heart.

Identifying the SA node as the heart's primary pacemaker is crucial for understanding cardiac physiology, as disturbances in its function can lead to various dysrhythmias.