Definition: Hart, also known as a heart or atrium, is a muscular tube in the human body that connects the left side of the heart with the right side and is responsible for pumping blood throughout the body. It contains two chambers, the right atrium and the left atrium, which together form the atrioventricular (AV) node. The AV node is where the electrical impulses from the atrial muscles are transmitted to the ventricles, or heart chambers, which pump blood back