Given a text passage, come up with an appropriate title for it. The title should accurately represent what the main focus of the passage is. The title of a passage may be present in the first few sentences of the passage and/or be referred to multiple times in the passage. The title should be 1-5 words long.

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 .
Myelin