The Physiology of the Human Heart The constant beating of the
heart is controlled by the conducting system of the heart, which
is a series of specialized nerve tissues that fire through the
heart and coordinate the actions of the heart beat: Sinoatrial
(SA) node: This pacemaker initiates the impulse. It’s located
anterolaterally just under the epicardium where the superior
vena cava enters the right atrium. The impulse from the
sinoatrial node spreads through the myocardium of the right and
left atria, and it’s also quickly transmitted to the
atrioventricular node. Atrioventricular (AV) node: This node is
located in the posterior and inferior portion of the interatrial
septum, close to the opening of the coronary sinus in the right
atrium. From there the signal is transmitted to the ventricles
by a bundle of nerves called the atrioventricular bundle.
Atrioventricular bundle: This bundle of nerves runs from the
atrioventricular node to the ventricles along the
interventricular septum. It divides into left and