Myeliinöityminen

Myeliinöityminen is the process by which nerve fibers, or axons, become coated with a fatty insulating sheath called myelin. This process is crucial for the proper functioning of the nervous system. Myelin is produced by specialized glial cells: oligodendrocytes in the central nervous system (brain and spinal cord) and Schwann cells in the peripheral nervous system (nerves outside the brain and spinal cord).

The myelin sheath is not continuous along the axon. It is formed in segments, separated by small gaps known as nodes of Ranvier. This segmented structure is essential for efficient nerve impulse transmission. Myelin acts as an electrical insulator, preventing the leakage of electrical current from the axon.

In myelinated axons, the nerve impulse jumps from one node of Ranvier to the next in a process called saltatory conduction. This significantly speeds up the transmission of signals compared to unmyelinated axons, where the impulse must travel along the entire length of the axon. This increased speed is vital for rapid reflexes, complex motor control, and efficient sensory processing.

Myeliinöityminen begins during fetal development and continues into adolescence and early adulthood. The degree of myelination influences cognitive abilities and motor skills. Disruptions or damage to the myelin sheath, a condition known as demyelination, can lead to severe neurological disorders such as multiple sclerosis, where nerve signal transmission is impaired, causing a range of symptoms including weakness, numbness, and coordination problems.