The Intrinsic Conduction System (Nodal System)

1. Sinoatrial (SA) Node

The SA node in the right atrium triggers atrial depolarization and contraction, which pushes blood into the ventricles through the atrioventricular valves.

2. Atrioventricular (AV) Node

The AV node receives the impulse and delays it briefly, which allows for the ventricles to finish filling with blood before contracting.

3. Atrioventricular Bundle (Bundle of His)

The atrioventricular bundle carries the impulse from the AV node into the interventricular septum, which bridges the electrical signal from the atria to ventricles.

4. Right and Left Bundle Branches

The right and left bundle branches carry the impulse down both sides of the interventricular septum toward the apex, preparing the ventricles for contraction.

5. Purkinje Fibers

The purkinje fibers quickly distribute the impulse down the ventricular walls, triggering ventricular depolarization and contraction, which forces blood out the semilunar valves into the pulmonary trunk and aorta.