the purkinje fibers are responsible for sending the electrical impulse into which area of the heart
Purkinje fibers During the ventricular contraction portion of the cardiac cycle, the Purkinje fibers carry the contraction impulse from both the left and right bundle branch to the myocardium of the ventricles. This causes the muscle tissue of the ventricles to contract and generate force to eject blood out of the heart, either to the pulmonary circulation from the right ventricle or to the systemic circulation from the left ventricle.[2]
Sinoatrial node The sinoatrial node (SA node), also known as sinus node, is a group of cells located in the wall of the right atrium of the heart.[1] These cells have the ability to spontaneously produce an electrical impulse (action potential; see below for more details), that travels through the heart via the electrical conduction system (see figure 1) causing it to contract. In a healthy heart, the SA node continuously produces action potential, setting the rhythm of the heart and so is known as the heart's natural pacemaker. The rate of action potential production (and therefore the heart rate) is influenced by nerves that supply it.[2]