Your heart is a four-chambered pump, made of muscle tissue. Like other muscle tissue, the tissue of the heart contracts when it is stimulated by electricity. The healthy heart has a natural system of electrical pathways that direct stimulation through the tissue. This stimulation causes the heart muscle to contract. The contraction pumps blood and nutrients throughout your body.

Electrical signals in a healthy heart begin at the sinus node, the heart’s electrical control center. From the sinus node, the electrical signal spreads across the heart’s upper chambers (atria), making them pump. Then, the signal travels to an electrical junction in the middle of the heart (AV node). The AV node conducts the electrical signals to the heart’s lower chambers (ventricles). After the lower chambers have finished pumping, the sinus node initiates the next rhythm.

A healthy sinus node will react to your body’s need for oxygen and nutrients by pumping faster during activity and slower during rest. Typically, a healthy heart will beat 60 to 80 beats per minute during rest. We usually do not notice our heart beating unless it does something unusual, such as slowing down, speeding up, or beating irregularly. A heart that beats irregularly may have a heart rhythm disorder caused by a problem with the heart’s electrical system. These problems are known as cardiac arrhythmias.