The aim of this lecture is to present on how to control of the Heart Beat. The heart is made up of cardiac muscle. Cardiac muscle is myogenic, which means it naturally contracts and relaxes. Therefore, it receives no impulse from a nerve to make it contract. The cardiac cycle is initiated by a small patch of muscle called the Sinoatrial node or pacemaker. This node sets the rhythm for all the other cardiac muscle. Pacemaker cells have an inbuilt rhythm that is faster than the other cells in the heart. The SA node sends out an excitation wave of electrical activity over the atrial walls. The cardiac muscle responds to this wave by contracting at the same speed as the SAN. This results in both atria contracting simultaneously.