61. What causes your heart to beat? The electrical system of your heart is the power source that makes this possible. The impulse starts in a small bundle of specialized cells located in the right atrium, called the SA node. The electrical activity spreads through the walls of the atria and causes them to contract. This forces blood into the ventricles.

61. What causes your heart to beat?

The electrical system of your heart is the power source that makes this possible. The impulse starts in a small bundle of specialized cells located in the right atrium, called the SA node. The electrical activity spreads through the walls of the atria and causes them to contract. This forces blood into the ventricles.