Myeliiniseinämä

Myeliiniseinämä refers to the myelin sheath that surrounds nerve fibers, also known as axons, in the vertebrate nervous system. This sheath is a fatty insulating layer that is crucial for the efficient transmission of nerve impulses. It is formed by specialized glial cells: Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system. These cells wrap their cell membranes around the axon multiple times, creating a multi-layered structure that significantly increases the speed at which electrical signals travel along the neuron.

The myelin sheath is not continuous. It is interrupted at regular intervals by gaps called nodes of Ranvier. These nodes are essential for saltatory conduction, a process where the nerve impulse "jumps" from one node to the next, rather than propagating continuously along the axon. This jumping mechanism dramatically speeds up signal transmission and conserves energy. The presence and integrity of the myelin sheath are vital for normal neurological function. Damage to the myelin sheath, a condition known as demyelination, can lead to a variety of neurological disorders, such as multiple sclerosis, where nerve signal transmission is severely impaired. The term "myeliiniseinämä" emphasizes the structural, wall-like nature of this protective and conductive layer around the axon.