314.996.5000

Health Library

Anatomy and Function of the Heart's Electrical System

Electical system of the heart
Click image to enlarge

The heart's electrical system

The heart is, in the simplest terms, a pump made up of muscle tissue. Like all muscle, the heart requires a source of energy and oxygen in order to function. The heart's pumping action is regulated by an electrical conduction system that coordinates the contraction of the various chambers of the heart.

How does the heart beat?

An electrical stimulus is generated by the sinus node (also called the sinoatrial node, or SA node). This is a small mass of specialized tissue located in the right atrium (right upper chamber) of the heart. The sinus node generates an electrical stimulus regularly (60 to 100 times per minute under normal conditions). The atria are then activated. The electrical stimulus travels down through the conduction pathways (similar to the way electricity flows through power lines from the power plant to your house) and causes the heart's ventricles to contract and pump out blood. The right and left atria (the two upper chambers of the heart) are stimulated first and contract for a short period of time before the right and left ventricles (the two lower chambers of the heart). 

The electrical impulse travels from the sinus node to the atrioventricular node (also called AV node). There, impulses are slowed down for a very short period, then continue down the conduction pathway via the bundle of His into the ventricles. The bundle of His divides into right and left pathways to provide electrical stimulation to the right and left ventricles.

Normally at rest, as the electrical impulse moves through the heart, the heart contracts about 60 to 100 times a minute, depending on a person's age.

Each contraction of the ventricles represents one heartbeat. The atria contract a fraction of a second before the ventricles so their blood empties into the ventricles before the ventricles contract.

Interactive Tools

Calculators
Try out these calculators: they're fun, they're quick, and they give you important information for managing your health.

Quizzes
Informative and often surprising, these quizzes test your knowledge of today's health concerns. Find out your score and learn more about these pertinent health issues.

Risk Assessments
Get insight into your health risks by using these assessment tools. They're easy to use and give you a quick snapshot of your likelihood to develop these common conditions.

Latest Health News
Copyright © 1997-2014 BJC HealthCare. All Rights Reserved.