myelinisation

Myelinisation is the biological process in which myelin sheaths are produced around the axons of neurons, increasing the speed and efficiency of electrical signal transmission along nerve fibers. In the central nervous system, oligodendrocytes extend their processes to enwrap multiple axons, forming concentric layers of lipid-rich myelin. In the peripheral nervous system, Schwann cells myelinate a single axon each, with each cell creating many turns of the myelin membrane. The myelin layers are built from phospholipids and proteins such as myelin basic protein and proteolipid protein, creating a compact insulating membrane separated from the axonal surface by a thin space known as the periaxonal region.

Myelinisation begins in embryonic development and continues through infancy and adolescence. In humans, essential myelin formation begins roughly in the second trimester, is largely established by birth for major pathways, and peaks during adolescence as part of brain maturation. Proper myelination is critical for rapid saltatory conduction, allowing action potentials to jump between node of Ranvier gaps. Disruptions in myelinisation can lead to neurological disorders such as multiple sclerosis, Charcot–Marie–Tooth disease, and dyslexia, highlighting its importance for normal nervous system function.

The process is regulated by a complex interplay of transcription factors, growth factors, and cell–cell interactions. Advances in imaging and molecular biology are increasingly revealing the timing, regional specificity, and mechanisms of myelinisation, offering insights for therapeutic strategies in demyelinating conditions.