Purkinje fibers are located in the inner ventricular walls of the heart, just beneath the endocardium. These fibers are specialized myocardial fibers that cause an electrical stimulus or impulse that enables the heart to contract in a coordinated fashion. Purkinje fibers work with the sinoatrial node (SA node) and the atrioventricular node (AV node) to control the heart rate.
During the ventricular contraction portion of the cardiac cycle, the Purkinje fibers carry the contraction impulse from the left and right bundle branches to the myocardium of the ventricles. This causes the muscle tissue of the ventricles to contract and force blood out of the heart — either to the pulmonary circulation (from the right ventricle) or to the systemic circulation (from the left ventricle).
They were discovered in 1839 by Jan Evangelista Purkinje, who gave them his name.