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Part of the conducting system of the heart. It lies near the orifice of the coronary sinus in the annular and septal fibers of the right atrium. Although it can generate its own pacemaker potential it generally receives a signal from the sinoatrial node which fires it earlier than it would fire of its own accord.
From the AV node the atrioventricular bundle passes forward in the lower part of the membranous septum, and divides into right and left fasciculi. Blockage of conduction down one or other of these fasiculi give the characteristic ECG appearances of bundle branch block.