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electrical system

Your Heart’s Electrical System & How Clots Form: An Introduction 

Basic introduction to how the heart works. Identifies the parts of the heart and illustrates the role of each, and shows how clots form; Detail animation of the heart processes accompanied by narration. Transcript below. (3:50 min.)

Animation from the National Heart Lung and Blood Institute.

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Transcript of this Article
Your heart’s electrical system controls all the events that occur when your heart pumps blood. The electrical system also is called the cardiac conduction system. If you’ve ever seen the heart test called an EKG (electrocardiogram), you’ve seen a graphical picture of the heart’s electrical activity.

Your heart’s electrical system is made up of three main parts:

The sinoatrial (SA) node, located in the right atrium of your heart
The atrioventricular (AV) node, located on the interatrial septum close to the tricuspid valve
The His-Purkinje system, located along the walls of your heart’s ventricles

A heartbeat is a complex series of events. These events take place inside and around your heart. A heartbeat is a single cycle in which your heart’s chambers relax and contract to pump blood. This cycle includes the opening and closing of the inlet and outlet valves of the right and left ventricles of your heart. Each heartbeat has two basic parts: diastole and systole.

During diastole, the atria and ventricles of your heart relax and begin to fill with blood. At the end of diastole, your heart’s atria contract (atrial systole) and pump blood into the ventricles. The atria then begin to relax.

Your heart’s ventricles then contract (ventricular systole), pumping blood out of your heart. Each beat of your heart is set in motion by an electrical signal from within your heart muscle. In a normal, healthy heart, each beat begins with a signal from the SA node. This is why the SA node sometimes is called your heart’s natural pacemaker.

Your pulse, or heart rate, is the number of signals the SA node produces per minute. The signal is generated as the vena cavae fill your heart’s right atrium with blood from other parts of your body. The signal spreads across the cells of your heart’s right and left atria. This signal causes the atria to contract. This action pushes blood through the open valves from the atria into both ventricles.

The signal arrives at the AV node near the ventricles.

It slows for an instant to allow your heart’s right and left ventricles to fill with blood. The signal is released and moves along a pathway called the bundle of His, which is located in the walls of your heart’s ventricles.

From the bundle of His, the signal fibers divide into left and right bundle branches through the Purkinje fibers. These fibers connect directly to the cells in the walls of your heart’s left and right ventricles (see yellow on the picture in the animation).

The signal spreads across the cells of your ventricle walls, and both ventricles contract. However, this doesn’t happen at exactly the same moment.

The left ventricle contracts an instant before the right ventricle. This pushes blood through the pulmonary valve (for the right ventricle) to your lungs, and through the aortic valve (for the left ventricle) to the rest of your body.

As the signal passes, the walls of the ventricles relax and await the next signal.

This process continues over and over as the atria refill with blood and more electrical signals come from the SA node.

If you find any errors on this page, email us. Y Last updated: Monday, September 11, 2017

Return to Instructional A-Fib Videos and Animations

It’s Back! Print a High-Quality Illustration of the Heart’s Electrical System

Click to download

Update March 24: The Cleveland Clinic has given us permission to host this graphic of the Heart’s Electrical System on A-Fib.com for the viewing and printing by our readers.

Print and keep this illustration handy for the next time you talk with your doctor about the workings of your heart. Draw and make notes directly on the picture. Add comments in the text box we added at the bottom.

To get yours, just download and store on your hard-drive. To have one handy when you need it, print and store copies in your “A-Fib Binder or folder“.

Download the illlustration.

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High-Quality Illustration of the Heart’s Electrical System

The Heart's Electrical System Illustration

The Heart’s Electrical System: Click image to download

Update March 24: The Cleveland Clinic has given us permission to host this graphic on A-Fib.com for the viewing and printing by our readers.

Print and keep this illustration handy for the next time you talk with your doctor about the workings of your heart. You can make notes directly on the picture.

Download the PDF file and store on your hard-drive. To have one handy when you need it, print and store copies in your “A-Fib Binder or folder“.
A-Fib.com Library of videos and animations

Video: You may also want to watch the video, How Your Heart Works and Understanding Arrhythmias, or one of several heart animations from our A-Fib.com Video & Animations Library.

Also see our Free Offers and Downloads page.

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