For proper function, the heart’s four chambers must beat in an organized way. The electrical impulse starts in a small bundle of highly specialized cells called the sinoatrial (SA) node, which is located in the right atrium. This electrical impulse then moves across the heart’s chambers in the order that they contract, or beat. The SA node is called the “natural pacemaker.” These electrical impulses are generated at a given rate, but emotional reactions and hormonal factors can adjust the rate of discharge to allow the heart rate to respond to varying demands.
A video that shows detailed information on how the heart’s conduction system works can be found at the American Heart Association.
Texas Heart Institute www.texasheartinstitute.com/HIC/Anatomy/conduct.cfm
American Heart Association www.americanheart.org/presenter.jhtml?identifier=34