Myeliniseerde

Myeliniseerde refers to nerve fibers or axons that are enclosed by a myelin sheath. Myelin is a lipid-rich layer produced by glial cells, which insulate and protect the axon. In the central nervous system (CNS), oligodendrocytes extend processes to several nearby axons; in the peripheral nervous system (PNS), Schwann cells wrap around a single axon segment.

The myelin sheath serves as an electrical insulator, increasing membrane resistance and reducing membrane capacitance. This arrangement enables saltatory conduction, where electrical impulses jump from one node of Ranvier to the next, greatly speeding up signal transmission and improving energy efficiency.

Myelination begins during prenatal development and continues after birth, with a region- and species-specific sequence. In humans, myelination proceeds in waves across neural tracts and can extend into adolescence, reflecting the maturation of neural circuits and higher cognitive functions.

Damage or loss of myelin disrupts signal transmission, leading to a range of neurological symptoms. Demyelinating diseases include multiple sclerosis and other inflammatory or autoimmune conditions affecting the CNS, as well as Guillain-Barré syndrome and related disorders impacting the PNS. Genetic leukodystrophies alter myelin formation or maintenance and can cause progressive neurological decline.

Notes: The term emphasizes the presence of a myelin sheath around axons. Not all fibers are myelinated; unmyelinated fibers conduct more slowly but can still transmit impulses. Nodes of Ranvier are gaps in myelin that facilitate rapid conduction.