myelinating

Myelinating describes the developmental process by which glial cells form the myelin sheath around axons, increasing the speed and efficiency of electrical signaling in the nervous system. In the central nervous system, myelination is carried out by oligodendrocytes; in the peripheral nervous system, Schwann cells perform the task.

During myelination, glial membranes wrap around segments of axons, creating insulating layers separated by gaps known as nodes of Ranvier. Oligodendrocytes can extend processes to several nearby axons, forming multiple internodes, whereas Schwann cells typically myelinate a single axon segment.

The myelin sheath is rich in lipids and specialized proteins that stabilize the membrane. CNS myelin contains proteins such as myelin basic protein (MBP) and proteolipid protein (PLP); PNS myelin includes proteins such as myelin protein zero (P0) and peripheral myelin protein 22 (PMP22).

Functionally, myelination increases nerve conduction velocity through saltatory conduction, reduces metabolic cost by minimizing membrane surface area requiring active ion pumps, and supports rapid maturation of neural circuits.

Timing and regulation of myelination are region- and age-dependent, influenced by neuronal activity and signaling pathways involving growth factors and transcriptional programs. Disruptions in myelination can affect neural communication and are linked to various neurological conditions.

Clinical relevance includes demyelinating diseases such as multiple sclerosis, which affects CNS myelin, and Guillain-Barré syndrome or CIDP, which involve PNS myelin. Genetic leukodystrophies reflect inherited defects in myelin formation or maintenance, illustrating the critical role of myelinating processes in nervous system function.