Conducting System of Human Heart:
The heart is able to both set its own rhythm and conduct the signals necessary to maintain and coordinate this rhythm throughout its structures. About 1% of the cardiac muscle cells in the heart are responsible for forming the conduction system that sets the pace for the rest of the cardiac muscle cells.
The conduction system starts with the pacemaker of the heart. It is a small bundle of cells known as the sinoatrial node (SA). The SA node is located in the wall of the right atrium inferior to the superior vena cava. The SA node is responsible for setting the pace of the heart as a whole and directly signals the atria to contract. The signal from the SA node is picked up by another mass of conductive tissue known as the atrioventricular node (AV).