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
Cardiac neural crest cells Cardiac neural crest cells Neural crest cells are a group of temporary, multipotent (can give rise to some other types of cells but not all) cells that are pinched off during the formation of the neural tube (precursor to the spinal cord and brain) and therefore are found at the dorsal (top) region of the neural tube during development. They are derived from the ectoderm germ layer, but are sometimes called the fourth germ layer because they are so important and give rise to so many other types of cells. They migrate throughout the body and create a large number