How does the heart beat?

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Electrical impulses are generated by the sinoatrial node (SA node), a small area in the heart's right upper chamber (atrium). As the electrical impulses travel smoothly through the heart, the two upper chambers (the atria) squeeze at the same time to pump blood down to the lower chambers (the ventricles). Then the two ventricles squeeze at the same time, pumping blood to your lungs to pick up oxygen and to the rest of your body. The heart beats regularly and evenly, about 60 to 100 times a minute.
The heart is, in the simplest terms, a pump made up of muscle tissue. Like all pumps, 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.

An electrical stimulus is generated by the sinus node (also called the sinoatrial node, or SA node), which 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 (60-100 times per minute under normal conditions). This 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 lower chambers to contract and pump out blood. The right and left atria (the two upper chambers of the heart) are stimulated first and contract 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), where 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 140 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.

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.
Atul Bhatia, MD
Clinical Cardiac Electrophysiology
The heart is a hollow, muscular organ that pumps blood throughout the body. The heart has four chambers, two upper (atria) and two lower (ventricles). The heart depends on its electrical system to deliver signals and make the heart beat normally.

For a normal heartbeat, an electrical signal starts in the sinus node, travels through the right and left atria, then through the AV node to the right and left ventricles. If a signal starts in a different location, it travels an abnormal pathway.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.