Identify the correct statement
I. The impulse of the heart beat originates from SAN
II. Rate of the heart is determined by SAN
III. Bundle of His/AV bundle is present in the interventricular septum
IV. Atrio Ventricular Node (AVN) is situated in the lower left corner of the right auricle
Choose the correct option :

All except III.
Automatic rhythmicity of the heart is the ability to contract spontaneously. Mammalian heart is myogenic. It means heart beat results from a wave of electrical potential called cardiac impulse arising from sinoatrial node SA node and spreading over cardiac chambers. SA-node lies in the wall of right atrium near opening of superior vena cava and contract about 72 times per minute. Form 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.