How is heart action initiated and coordinated

- process starts in the sino-atrial node (SAN), in the walls of the right atrium - SAN sends out regular waves of electrical activity to the atrial walls - this causes the right and left atrium to contract at the same time - the waves of the electrical activity are transferred from the SAN to the atrioventricular node (AVN) - AVN passes electrical activity to bundle of His, but there's a slight delay - this ensures that ventricles contract after atria have emptied - bundle of His conducts waves of electrical activity to Purkyne tissue - Purkyne tissue carries waves of electrical activity to walls of right and left ventricles, causing them to contract simultaneously from bottom up