The Heart's Electrical System

Your heart is a muscle that works like a pump. The main job of your heart is to pump blood throughout your body. The heart is divided into a right and left side. Each side has an upper chamber, or atrium, that collects blood returning to the heart and a muscular lower chamber, or ventricle, that pumps the blood away from the heart.

Medical illustration of a heart showing the left and right atria, which collect blood returning to the heart, and the left and right ventricles, which pump the blood away from the heart.

The pumping of your heart is regulated by an electrical current, or impulse, much like a spark plug in a car. The electrical impulse starts in the sinoatrial (SA) node, often called the body’s natural pacemaker, and then spreads throughout both atria, like ripples in a pond. This causes both atria to contract, squeezing blood into the ventricles.

The impulse then travels down to the atrioventricular (AV) node, which is like a wire that connects to the ventricles. The AV node splits into two branches, allowing the even spread of the electrical signal to both ventricles at the same time. This lets your heart beat effectively.

Medical illustration of a heart showing the sinoatrial node, the atrioventricular node, and the left and right bundle branches, which control the electrical impulse that causes your heart to pump.