The sinoatrial (SA) node is a critical component of the heart's conduction system, which regulates heart rate. This intricately designed system produces electrical impulses that travel through the heart muscle, prompting it to contract and pump blood. The SA node acts as the heart's natural pacemaker. It is composed of a cluster of cells located in the upper section of the wall of the right atrium, where these impulses originate. The SA node is also referred to as the heart's pacemaker.The electrical signal from the SA node is transmitted from one cell to another until it reaches the atrioventricular (AV) node, which is a group of cells located centrally in the heart between the atria and the ventricles. The AV node functions as a gateway that delays the electrical impulse, allowing the atria to fully contract before the ventricles are activated. Once past the AV node, the electrical impulse travels through specialized fibers embedded in the walls of the heart's lower chambers.The autonomic nervous system, which also manages blood pressure, regulates the firing of the SA node to initiate the cardiac cycle. It can rapidly signal the SA node to double the heart rate within just 3 to 5 seconds, a vital response during physical activity when the heart needs to meet the body's increased oxygen demands.
