myeliniserat

Myeliniserat is an adjective used to describe nervous-system fibers that are insulated with a myelin sheath. In vertebrates, most long axons are myelinated; the myelin sheath is produced by oligodendrocytes in the central nervous system and by Schwann cells in the peripheral nervous system.

The myelin sheath consists of multiple concentric layers of lipid-rich membrane wrapped around the axon, forming segments separated by nodes of Ranvier. This arrangement increases the speed of electrical conduction through saltatory conduction and reduces energy expenditure for signaling.

Development and variation: Myelination begins during fetal development and continues after birth, with timing and extent varying by region and neuron type. In the CNS, oligodendrocytes extend processes to multiple axons; in the PNS, individual Schwann cells wrap segments of a single axon.

Function and clinical relevance: Myelination supports rapid and coordinated neural signaling, enables high-frequency firing, and protects axons metabolically. Demyelinating diseases — for example multiple sclerosis in the CNS and Guillain–Barré syndrome in the PNS — disrupt conduction and produce neurological symptoms. Remyelination can occur, especially in the peripheral nervous system, but may be incomplete.

Unmyelinated fibers exist, particularly among small-diameter axons, and not all neurons are myelinated. Myelin is a characteristic feature of most vertebrate nervous systems and is not present in most invertebrates.