the myelin sheath that covers many cns axons is formed by
Myelin Myelin is a lipid-rich (fatty) substance formed in the central nervous system (CNS) by glial cells called oligodendrocytes, and in the peripheral nervous system (PNS) by Schwann cells. Myelin insulates nerve cell axons to increase the speed at which information (encoded as an electrical signal) travels from one nerve cell body to another (as in the CNS) or, for example, from a nerve cell body to a muscle (as in the PNS). The myelinated axon can be likened to an electrical wire (the axon) with insulating material (myelin) around it. However, unlike the plastic covering on an electrical wire, myelin does not form a single long sheath over the entire length of the axon. Rather, each myelin sheath insulates the axon over a single section and, in general, each axon comprises multiple long myelinated sections separated from each other by short gaps. Each myelin sheath is formed by the concentric wrapping of an oligodendrocyte or Schwann cell process around the axon.
Nervous tissue The function of nervous tissue is to form the communication network of the nervous system by conducting electric signals across tissue.[12] In the CNS, grey matter, which contains the synapses, is important for information processing. White matter, containing myelinated axons, connects and facilitates nerve impulse between grey matter areas in the CNS.[13] In the PNS, the ganglion tissue, containing the cell bodies and dendrites, contain relay points for nerve tissue impulses. The nerve tissue, containing myelinated axons bundles, carry action potential/nerve impulses.[10]