A pacemaker, which depolarizes spontaneously, establishes the rate of contraction of the heart muscle. The most common pacemaker of the heart is called the AV node.
O establishes a resting heart rate of about 60 to 80 contractions per minute.
O functions also under the control of both the sympathetic and the parasympathetic nervous systems.
O is located in the muscle of the left atrium.
O Two of the above are true.