Electrical Conduction Heart Impulse

In a normal heart, the sinoatrial node, or SA node is considered the "pacemaker" of the heart. It is located in the right atrium. Impulses originate in the SA node and cause atrial contraction, and subsequently spread throughout the heart. Once the impulse spreads through the atria, it passes to the atrioventricular or AV node down the septum of the heart. The impulse causes contraction of the ventricles as it travels to the inferior portions of the heart through the right and left bundle branches and ultimately to the purkinje fibers in the inferior part of the ventricles, which causes ventricular contraction. Some abnormalities in the tissue of the heart will create electrical pathway disturbances (or blocks) of impulses and require external mechanisms such as pacemakers to sustain the normal heart rate.