How does your heart work 24 hours a day
The atria and ventricles work together by alternately contracting (squeezing) and relaxing to pump blood through your heart. The heartbeat is triggered by electrical impulses that travel down a special pathway through your heart. The electrical system of your heart is the power source that makes this beating possible.
http://www.capitalcardiology.com/heartwork.htm
the heart is a mucle. There are primarily two type of muscles Voluntary - hmmm I think I will raise my arm right now... there it goes!! involuntary - how do I mak my heart stop? ready.. stop!!... hey its still going!!