Cardiac pacemaker in adult humans is about 70 beats per minute. Because the sinoatrial node is responsible for the rest of the heart's electrical activity, it is sometimes called the "primary pacemaker". If the SA node does not function properly and is unable to control the heart rate, a group of cells further down the heart will become the ectopic pacemaker of the heart. These cells form the Atrioventricular node (or AV node), which is an area between the left atrium and the right ventricle within the atrial septum, will take over the pacemaker responsibility. The cells of the AV node normally
Purkinje fibers the nucleus causes Purkinje fibers to appear, on a slide, lighter and larger than their neighbors, arranged along the longitudinal direction (parallel to the cardiac vector). They are often binucleated cells. Heart rate is governed by many influences from the autonomic nervous system. The Purkinje fibres do not have any known role in setting heart rate unless the SA node is compromised. They are influenced by electrical discharge from the sinoatrial node. During the ventricular contraction portion of the cardiac cycle, the Purkinje fibres carry the contraction impulse from both the left and right bundle branch to the myocardium of