A Perfect Pump

Your heart is a strong muscle that pumps blood throughout your body.  It has four chambers: two on the left side and two on the right side.

The upper chambers called the atriums receive and collect blood.  The lower chambers on each side, called ventricles, pump blood out of the heart.

The four chambers work together to contract (squeeze) and pump blood.  As your blood circulates it delivers oxygen and nutrients to your body.

The Electrical System

The upper and lower chambers know when to pump because they receive electrical messages from the heart's electrical system. This system produces electrical impulses.

The electrical impulses start at the sinoatrial node (SA node) located at the top of the right atrium and spread out to the atria (plural of atrium). This tells the atria to contract and pump blood into the ventricles.  These impulses set the rhythm for the heartbeat.  The SA node is known as the hearts natural pacemaker.

The impulses then reach the atrial ventricular node (AV node) located between the atria and ventricles.  The AV node slows the electrical impulses before it enters the ventricles.

The impulse travels to the ventricles through conduction pathways and causes the ventricles to contract and pump blood out of the heart.

At rest the SA node causes the normal heart to beat at between 60 and 100 beats per minute.  The SA node responds to physical exertion or excitement by increasing the number of beats per minute (heart rate) to provide the body with more blood flow.

Learn more about the anatomy of  your heart and view a video about the workings of your heart.