Cardiac pacemaker heart. There are 3 main stages in the generation of an action potential in a pacemaker cell. Since the stages are analogous to contraction of cardiac muscle cells, they have the same naming system. This can lead to some confusion. There is no phase 1 or 2, just phases 0, 3, and 4. The key to the rhythmic firing of pacemaker cells is that, unlike other neurons in the body, these cells will slowly depolarize by themselves and do not need any outside innervation from the autonomic nervous system to fire action potentials. As in all other cells, the resting
Cardiac neural crest cells to replace the necrotic tissue. 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