onvermyeliniseerde

Onvermyeliniseerde refers to nerve fibers that lack a myelin sheath. Myelin is a fatty insulating layer that surrounds the axons of many neurons, acting similarly to the insulation on an electrical wire. This sheath is produced by glial cells, specifically oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. The presence of myelin is crucial for rapid transmission of nerve impulses through a process called saltatory conduction, where the impulse "jumps" between gaps in the myelin called nodes of Ranvier.

Nerve fibers that are onvermyeliniseerde, therefore, conduct nerve impulses much more slowly than myelinated fibers. These unmyelinated axons are typically smaller in diameter than myelinated ones and are often involved in transmitting slower, more diffuse signals. Examples include C fibers, which carry pain, temperature, and itch sensations, as well as autonomic nervous system postganglionic fibers. While less efficient for rapid signal transmission, the lack of myelin allows for more flexibility and potentially denser packing of axons in certain neural pathways. Conditions affecting the production or maintenance of myelin, such as demyelinating diseases, can lead to significant neurological dysfunction due to the impaired conduction of nerve signals. The term is derived from Dutch, meaning "unmyelinated."