these glue-like cells hold the nerve fibers together and produce myelin

The glue-like cells that hold nerve fibers together and produce myelin are called glial cells or neuroglia. Specifically, the type of glial cells responsible for producing myelin in the central nervous system (CNS) are called oligodendrocytes. In the peripheral nervous system (PNS), the myelin is produced by Schwann cells. These cells play a crucial role in supporting and protecting neurons, as well as facilitating the rapid transmission of electrical signals along nerve fibers.