How the Heart Contracts - Step by Step

  1. Electrical Impulse Initiation: The process begins in the sinoatrial (SA) node, where an electrical impulse is generated.

  2. Atrial Contraction: This impulse spreads through the atria, causing them to contract and push blood into the ventricles.

  3. AV Node Delay: The electrical signal then reaches the atrioventricular (AV) node, where it is momentarily delayed, allowing the ventricles to fill with blood.

  4. Ventricular Contraction: After the delay, the impulse travels through the bundle of His and into the Purkinje fibers, triggering the ventricles to contract and pump blood to the lungs and the rest of the body.