The order of impulse conduction in the heart, from beginning to end, is SA node, AV node, bundle of His, bundle branches, and Purkinje fibers.
SA node, or the sinus node, is the heart's natural pacemaker. AV node, or the atrioventricular node, spreads electrical impulses from the atria to the ventricles. The bundle of His, as well as bundle branches, are a part of the electrical conduction system of the heart. Purkinje fibers send nerve impulses through the heart.