What is the site of electrical connection between the atria and the ventricles?

Your Heart’s Electrical System

The heartbeat is the rhythmic squeezing (contraction) of the heart muscle's 4 chambers. The 4 chambers are called the right atrium, the right ventricle, the left atrium, and the left ventricle. The heart muscle has a system that creates and sends electrical signals to trigger the action of these 4 chambers. First, an electrical signal is made in the right upper chamber of the heart. This signal tells the 2 upper chambers (atria) to squeeze. This moves blood to the 2 lower chambers (ventricles). Next, the signals tell the ventricles to squeeze. This moves blood to the lungs, brain, heart, and body.

Electrical signals

Groups of specialized cells in the right atrium send out the heart’s electrical signals. These groups of cells are called nodes. The signals travel along pathways. In the ventricles, these pathways are called bundle branches.

The SA (sinoatrial) node

The SA usually sets the pace of the heartbeat. Each heartbeat is normally evenly spaced from beat to beat. It starts each beat by releasing an electrical signal. This signal tells the atria to squeeze. The resting rate for this is between 60 and 100 beats per minute.

The AV (atrioventricular) node

This group of specialized cells gets the electrical signals from the atria. It is like a "gatekeeper" between the atria and the ventricles. The AV node sends the signals into the ventricles after a delay. This lets the atria contract before the ventricles contract. If the sinus node fails to fire, the AV node may also kick in as a backup. It has a rate of 40 to60 beats per minute.

The bundle branches

These branches carry the electrical signals through the ventricle walls. This causes the ventricles to squeeze.

StayWell last reviewed this educational content on 7/1/2019

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Overview

The heart has four chambers. The two upper chambers are called atria (the right atrium and the left atrium), and the two lower chambers are called ventricles.

Normally, the heartbeat starts in the right atrium in a group of special heart cells called the sinoatrial (or sinus) node. These cells act as a pacemaker for the heart.

The heart's pacemaker sends out an electrical signal (impulse) that spreads throughout the heart along electrical pathways. These pathways transmit the signal from the upper to the lower chambers of the heart, which causes the heart muscle to contract. Regular, rhythmic electrical signals keep the heart pumping blood to the lungs and the body.

What controls the timing of your heartbeat?

Your heart's electrical system controls the timing of your heartbeat by regulating your:

• Heart rate, which is the number of times your heart beats per minute.
• Heart rhythm, which is the synchronized pumping action of your four heart chambers.

Your heart's electrical system should maintain:

• A steady heart rate of about 60 to 100 beats per minute at rest. The heart's electrical system also increases this rate to meet your body's needs during physical activity and lowers it during sleep.
• An orderly contraction of your atria and ventricles (this is called a sinus rhythm).

What makes your heart rate speed up or slow down?

The cells of the SA node at the top of the heart are known as the pacemaker of the heart because the rate at which these cells send out electrical signals determines the rate at which the entire heart beats (heart rate).

The normal heart rate for an adult at rest ranges between about 60 and 100 beats per minute. Your heart rate can adjust higher or lower to meet your body's needs.

Your brain and other parts of your body send signals to stimulate your heart to beat either at a faster or a slower rate. Although the way all of the chemical signals interact to affect your heart rate is complex, the net result is that these signals tell the SA node to fire charges at either a faster or slower pace, resulting in a faster or a slower heart rate.

For example, during periods of exercise, when the body requires more oxygen to function, signals from your body cause your heart rate to increase significantly to deliver more blood (and therefore more oxygen) to the body. Your heart rate can increase beyond 100 beats per minute to meet your body's increased needs during physical exertion.

Similarly, during periods of rest or sleep, when the body needs less oxygen, the heart rate decreases. Some athletes actually may have normal heart rates well below 60 because their hearts are very efficient and don't need to beat as fast. Changes in your heart rate, therefore, are a normal part of your heart's effort to meet the needs of your body.

Credits

Current as of: January 10, 2022

Author: Healthwise Staff
Medical Review:
Rakesh K. Pai MD, FACC - Cardiology, Electrophysiology
Martin J. Gabica MD - Family Medicine
Adam Husney MD - Family Medicine
George Philippides MD - Cardiology