Sequence of cardiac excitation Copyright@ The McGraw-Hill Companies, Inc. Permission required for reproduction or display Atrial excitation Ventricular excitation Ventricular relaxation Begins Complete SA node AV node Atrial Time Time Time Time Time The sinoatrial node is The Bundle of His and other parts the hearts pacemaker of the conducting system deliver because it initiates the excitation to the apex of the each wave of excitation heart so that ventricular contraction with atrial contraction occurs in an upward sweep.The sinoatrial node is the heart’s pacemaker because it initiates each wave of excitation with atrial contraction. The Bundle of His and other parts of the conducting system deliver the excitation to the apex of the heart so that ventricular contraction occurs in an upward sweep. Sequence of cardiac excitation