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Patient Education

How the Heart Works

The heart is muscular and hollow, constantly pumping blood to deliver oxygen and nutrients to the body. It's composed of four compartments, or chambers, two on the right side and two on the left. The upper chambers, called atriums, receive and collect blood. The lower chambers, called ventricles, pump blood to the body. Working together, the chambers of the heart move life-sustaining blood throughout the body.

The heart's rhythmic contractions are controlled by an electrical system sending impulses throughout the heart. The impulses begin at the sino-atrial (SA) node, a small mass of tissue near the right atrium that sets the pace for the heartbeat.

The impulse then spreads through the atria, causing a contraction and squeezing blood into the ventricles. From the atria, the impulse moves to the atrioventricular (AV) node, a small mass of tissue in the wall of the right atrium. The AV node slows the impulse coming from the atria before it passes through to the ventricles. Normally, the atrium is electrically insulated from the ventricle by fibrous tissue, except at the AV node. Through a specialized muscle fiber system, the impulse is distributed throughout both ventricles, causing them to contract and pump blood.

This normal transmission is called normal sinus rhythm, with a regular heartbeat of 60 to 100 times per minute.

UCSF Health medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.

Recommended reading

Diet and Congestive Heart Failure

Discover how a low-sodium diet can help you manage congestive heart failure (CHF) and learn how to adjust your eating habits for better overall heart health.

FAQ: Electrophysiology Study and Catheter Ablation

Find commonly asked questions regarding Electrophysiology Study and Catheter Ablation including, how long the procedure is, when to return to work and more.

FAQ: Heart Transplant

There are a number of things you can do to keep your heart healthy and reduce your risk of heart disease such as eating right and staying active. Learn more.

Heart and Vascular Disease: The Facts

Here are some tips from the UCSF Heart & Vascular Center to keep yourself informed and lower your risk of becoming another heart and vascular disease statistic.

Heart and Vascular Disease: The Risk Factors

Cardiovascular disease disorders of the heart or blood vessels is the number one cause of death and disability among adults in the U.S. Learn more.

Heart and Vascular Disease: Prevention Tips

The UCSF Nutrition Counseling Clinic answers questions about nutrition and heart health including, some of the biggest myths about heart-healthy foods.

Heart Healthy Tips

Physical activity, along with following a healthy diet and not smoking, is one of the most important things you can do to keep your heart and lungs healthy.

Holiday Tips for Heart Health

The UCSF Center for Prevention of Heart & Vascular Disease generated these tips after seeing cardiology patients struggle to maintain health during the holidays

Women and Cardiovascular Disease

Heart disease is the No. 1 killer of American women, and claims the lives of 1 in 3 women, or 500,000 women a year. Learn more here.

Key treatments

  • Catheter Ablation

  • Endovascular Surgery

  • Implantable Cardioverter Defibrillator (ICD)

Related clinics

Asian Heart and Vascular Center

1 Daniel Burnham Ct., Suite 260
San Francisco, CA 94109

(415) 353-2873

Cardiovascular Care and Prevention Center – Golden Gate Practice

1 Daniel Burnham Ct., Suite 260
San Francisco, CA 94109

(415) 502-5099
M-F, 8 a.m. - 4:30 p.m.

Cardiovascular Care and Prevention Center at Mission Bay

535 Mission Bay Blvd. South
San Francisco, CA 94158

(415) 353-2873
M-F, 8 a.m. - 5 p.m.

Center for Prevention of Heart and Vascular Disease

535 Mission Bay Blvd. South
San Francisco, CA 94158

(415) 353-2873
M-F, 8 a.m. - 5 p.m.
Did you know?

At any given time, UCSF is conducting more than 1,500 clinical trials to better understand disease and evaluate new treatments. Many treatments and diagnostic tools developed at UCSF are now in standard use around the world, while others are still only available here or at a handful of medical centers.

Learn more
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