SA-node lies in the wall of right atrium near opening of superior vena cava and contract about 72 times per minute. From SA node cardiac impulse travels to atrioventricular node (lies between right atrium and ventricle). Then pass to AV bundle (also called bundle to His) and its branches reaches to the Purkinje fibres in ventricles. Bundle of His provides the only route for the transmission of wave of excitation from atria to ventricles. Purkinje fibres conducts the impulses five times more rapidly than surrounding cells. It forms a pathway for conduction of impulse that ensures that the heart muscle contracts in the most efficient manner.

──────────────────────────────────────────────────────────────────────────────────────────