This node initiates impulses that spread throughout the myocardium and is self-exciting (-it does not require a signal from the nervous system).Impulses from the S-A node quickly spread throughout the atria and cause them to contract. Impulses also spread to the _ atrioventricular _____________ (A-V) node. The A-V node rapidly sends a signal down the ____AV______ bundle and into the interventricular septum. These impulses rapidly spread through ______Purkinje______ fibers into the walls of the ventricles and cause the ventricles to contract. ECG/EKG:The first wave, the ____P______ wave, corresponds to the _________depolarization__________ of theatria.The _____QRS_____ complex corresponds to the ___________________depolarization______ of ventricles and hides the _____repolarization_____________ of atria.The _____T____ waves end the ECG pattern and correspond to ventricular __repolarization_________________.Heart rate control:Cardiac Conduction System regulates heart rate at about 75 beats/minute. However, the amount of blood pumped at any one time must adjust to the current needs of the body (more blood needed during strenuous exercise).