myeliniserer

Myeliniserer (myelination) is the process by which glial cells form a myelin sheath around axons in the vertebrate nervous system. The myelin sheath increases the electrical resistance and decreases membrane capacitance, enabling rapid saltatory conduction of action potentials and improved energy efficiency. In the central nervous system (CNS) myelin is produced by oligodendrocytes; in the peripheral nervous system (PNS) by Schwann cells.

Structure: Myelin consists of multiple membrane wraps rich in lipids (especially cholesterol and sphingolipids) and specific proteins (MBP, PLP in CNS; PMP22, P0 in PNS). The sheath is interrupted at nodes of Ranvier, where voltage-gated Na+ channels cluster, enabling saltatory conduction. Myelin thickness correlates with axon diameter and increases conduction velocity roughly proportional to diameter and myelin thickness.

Development: Myelination begins in prenatal development and continues postnatally, with regional and species variations. In humans, brain regions myelinate in a protracted sequence, from brainstem and spinal cord to cortex, continuing into adolescence and early adulthood. Activity and neuronal signaling can influence myelination patterns.

Clinical relevance: Disruption of myelin—through demyelinating diseases such as multiple sclerosis (CNS) and Guillain-Barré syndrome (PNS)—impairs signal conduction and can cause neurologic deficits. Remyelination can occur, mediated by progenitor cells, but often fails in chronic disease. Understanding myeliniserer is important for neurology and neurodevelopment research.