SA Node
pacemaker 60-100 bpm
The sinoatrial (SA) node, also known as the sinus node, is a small group of specialized cells located in the right atrium of the heart. It acts as the primary pacemaker of the heart by generating electrical impulses that regulate the heart rate and rhythm. The SA node depolarizes spontaneously and generates an electrical impulse that travels through the atria, causing them to contract and push blood into the ventricles. The impulse then reaches the atrioventricular (AV) node, where it is delayed briefly to allow the ventricles to fill with blood before it is conducted through the bundle of His and Purkinje fibers to cause ventricular contraction. The SA node is regulated by the autonomic nervous system, with the parasympathetic nervous system (via the vagus nerve) slowing down the heart rate and the sympathetic nervous system (via the cardiac nerves) increasing it.
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