Heart muscle with purkinje fibers on the surface of heart muscle fibers. Purkinje fibers are modified cardiac muscle fibers that originate from the atrioventricular node and spread into the two ventricles. They transmit the electrical impulse from the atrioventricular node to the ventricles enabling almost simultaneous contraction. The spread of excitation through the ventricles from the atrioventricular node is extremely rapid, moving at one to four meters per second.
