How Does the Heart Beat?

The Heartbeat

Your heart is a muscular organ that acts like a pump to continuously send blood throughout your body. Your heartbeat occurs when the atria and ventricles work together, alternately contracting and relaxing to pump blood through your heart. The electrical system of your heart is the power source that makes this possible.

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

  1. SA node (sinoatrial node) - known as the heart's natural pacemaker
    The impulse starts in a small bundle of specialized cells located in the right atrium. The electrical activity spreads through the walls of the atria and causes them to contract.
  2. AV node (atrioventricular node) -
    A cluster of cells in the center of the heart between the atria and ventricles, the AV node is like a gate that slows the electrical signal before it enters the ventricles. This delay gives the atria time to contract before the ventricles do.
  3. His-Purkinje Network -
    This pathway of fibers sends the impulse to the muscular walls of the ventricles, causing them to contract.

The SA node fires another impulse and the cycle begins again.

How fast does the normal heart beat?

How fast the heart beats depends on the body's need for oxygen-rich blood. At rest, the SA node causes your heart to beat about 50 to 100 times each minute. During activity or excitement, your body needs more oxygen-rich blood; the heart rate rises to well over 100 beats per minute.

Medications and some medical conditions may affect how fast your heart-rate is at rest and with exercise.

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