Describe the control of heart rate

1.) First starts in the sino-atrial node. 2.) Sino-atrial node sends out regular waves of electricity to the atrial walls in order to initiate heart beat.3.) This leads to contraction of right and left atria.4.) A non-conducting band of collagen stops the electrical waves passing straight to the ventricles.5.) Some of these waves reach the atrioventricular node (AVN). This then passes waves of electricity down the bundle of His.6.) However, there is a delay before the AVN sends out its activity in order to allow the atria to fully empty. After the delay, the electrical waves pass down the bundle of His.7.)Bundle of His splits into thinner fibres splitting left and right. These are the Purkinje fibres.8.) The Purkinje fibres carry the electrical waves into muscular walls of the two ventricles leading them to contract simultaneously from the bottom up.