The
Heart 
|
|
The heart is able to circulate blood through the body by contracting rhythmically in a certain pattern. This contraction is caused by an electrical shock from the sinoatrial node (SA Node) that causes the atria to contract. The electrical impulse is then conducted through the atrioventricular node (AV Node) to the ventricles, which then contract. This forces the blood out into the body and the lungs. The black arrows in the diagram show the direction of blood-flow. An electrocardiogram (ECG) printout illustrates the electrical activity of the heart. |
On an ECG, one heartbeat can be isolated and broken into several portions. P is the contraction of the atria, QRS is the contraction of the ventricles, and T shows the ventricles repolarizing.
© 2005 Ana Marx
