How the Heart Works - Your Heart's Electrical System - Your Heart's Electrical System

Your heartbeat is the contraction of your heart to pump blood to your lungs and the rest of your body. Your heart's electrical system determines how fast your heart beats.

Your heartbeat
- How the Heart Works - Your Heart's Electrical System

The contraction of the atria and ventricles makes a heartbeat. When your heart beats, it makes a “lub-DUB” sound. You may have heard this if you listened with a stethoscope or with your ear on someone's chest.

  • After your atria pump blood into the ventricles, the valves between the atria and ventricles close to prevent backflow. The “lub” is the sound of these valves closing.
  • After your ventricles contract to pump blood away from the heart, the aortic and pulmonary valves close and make the “DUB” sound.

Your heart beats an average of 60 to 100 beats per minute. In that one minute, your heart pumps about five quarts of blood through your arteries, delivering a steady stream of oxygen and nutrients all over your body. Medical Animation Copyright © 2022 Nucleus Medical Media, All rights reserved.

What is my pulse, and how do I measure it?

Electrical activity
- How the Heart Works - Your Heart's Electrical System

Electrical signals cause muscles to contract. Your heart has a special electrical system called the cardiac conduction system. This system controls the rate and rhythm of the heartbeat.

With each heartbeat, an electrical signal travels from the top of the heart to the bottom. As the signal travels, it causes the heart to contract and pump blood. The heartbeat process includes the following steps.

  • The signal begins in a group of cells, called pacemaker cells, located in the sinoatrial (SA) node in the right atrium.
  • The electrical signal travels through the atria, causing them to pump blood into the ventricles.
  • The electrical signal then moves down to a group of pacemaker cells called the atrioventricular (AV) node, located between the atria and the ventricles. Here the signal slows down slightly, allowing the ventricles time to finish filling with blood.
  • The AV node fires another signal that travels along the walls of your ventricles, causing them to contract and pump blood out of your heart.
  • The ventricles relax, and the heartbeat process starts all over again in the SA node.

Some conditions affect the heart's electrical system. Examples include:

  • Arrhythmia, or an irregular heart rhythm. Atrial fibrillation is one of the most common types of arrhythmia.
  • Conduction disorders, in which electrical signals either do not generate properly, or they do not travel properly through the heart, or both.