SchwannZellHülle

SchwannZellHülle refers to the myelin sheath formed by Schwann cells in the peripheral nervous system. Schwann cells are a type of glial cell that ensheath the axons of neurons. In unmyelinated axons, a single Schwann cell envelops multiple axons loosely. However, in myelinated axons, a single Schwann cell wraps itself around a segment of a single axon, forming a multilayered insulating sheath known as the myelin sheath. This wrapping process involves the Schwann cell's cytoplasm and plasma membrane spiraling around the axon.

The myelin sheath is crucial for rapid nerve impulse conduction. Its lipid-rich composition acts as an electrical insulator, preventing the leakage of ions across the axonal membrane. This insulation forces the action potential to "jump" between unmyelinated gaps in the sheath called nodes of Ranvier. This saltatory conduction significantly increases the speed at which nerve signals travel compared to unmyelinated axons.

The SchwannZellHülle is not a continuous structure. It is segmented along the axon, with each segment produced by a different Schwann cell. The gaps between these segments are the nodes of Ranvier, which are essential for saltatory conduction. In cases of peripheral nerve damage, Schwann cells play a vital role in nerve regeneration. They clear debris from the damaged axon and then form a "Büngner band" that guides the regenerating axon sprout. This regenerative capacity is a key feature of the peripheral nervous system.