The conduction system of the heart

The heart has its own built-in electrical system, called the conduction system. The conduction system sends electrical signals throughout the heart that determine the timing of the heartbeat and cause the heart to beat in a coordinated, rhythmic pattern. The electrical signals, or impulses, of the heart are generated by a clump of specialized tissue called the sinus node. Each time the sinus node generates a new electrical impulse, that impulse spreads out through the heart's upper chambers, called the right atrium and the left atrium. This electrical impulse, as it spreads across the two atria, stimulates them to contract, pumping blood into the right and left ventricles. The electrical impulse then spreads to the atrioventricular (AV) node, which is another clump of specialized tissue located between the atria and the ventricles. The AV node momentarily slows down the spread of the electrical impulse, to allow the left and right atria to finish contracting. From the AV node, the impulse spreads into a system of specialized fibers called the His bundle and the right and left bundle branches. These fibers distribute the electrical impulse rapidly to all areas of the right and left ventricles, stimulating them to contract in a coordinated way. With this contraction, blood is pumped from the right ventricle to the lungs, and from the left ventricle throughout the body.