Describe the conducting system of the heart.

The pacemaker cells of the sino-atrial node in the right atrium generate an impulse.This impulse travels through the atria, causing depolarisation of cardiac muscle cells and atrial contraction.The impulse wave reaches the atrio-ventricular node at the junction between the atria and the ventricles.The atrio-ventricular node slows conduction.The impulse travels down the interventricular septum via the Bundle of His.The Bundle of His then separates into 2 branches, one for each ventricle.Each ventricle depolarises and contracts as the impulse reaches them via these branches.The cardiac muscle cells repolarise and stop contracting until another impulse reaches them.