And these myelin sheaths or simply myelin, help insulate our axon. And that means that increases the speed of propagation of the action potential along our axon. Now, within our central nervous system the cells responsible for actually creating the myelin around the axon are the liga denticides. So they use these extensions to wrap around specific regions of the axon and actually create those myelin. So let's move on to the fourth type known as microglia. So microglia are those cells that differentiate from monocides found inside the bone marrow.