Anatomy and Function of the Heart's Electrical System Click
Image to Enlarge The heart's electrical system The heart is, in
the simplest terms, a pump made up of muscle tissue. Like all
pumps, the heart requires a source of energy and oxygen in order
to function. The heart's pumping action is regulated by an
electrical conduction system that coordinates the contraction of
the various chambers of the heart. How does the heart beat? An
electrical stimulus is generated by the sinus node (also called
the sinoatrial node, or SA node). This is a small mass of
specialized tissue located in the right atrium (right upper
chamber) of the heart. The sinus node generates an electrical
stimulus regularly (60 to 100 times per minute under normal
conditions). The atria are then activated. The electrical
stimulus travels down through the conduction pathways (similar
to the way electricity flows through power lines from the power
plant to your house) and causes the heart's ventricles to
contract and pump out blood. The right