Ranvierszakaszok

Ranvierszakaszok, also known as nodes of Ranvier, are periodic gaps in the myelin sheath that covers axons of nerve cells. These gaps are essential for the rapid conduction of nerve impulses through a process called saltatory conduction. The myelin sheath, produced by glial cells (oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system), acts as an electrical insulator. However, this insulation is not continuous along the axon.

The unmyelinated gaps, the nodes of Ranvier, expose the axon membrane to the extracellular fluid. This exposure allows for the influx of sodium ions, which depolarizes the membrane and triggers an action potential. Instead of propagating continuously along the entire axon, the action potential "jumps" from one node to the next. This leaping mechanism significantly increases the speed of nerve impulse transmission compared to continuous conduction in unmyelinated axons. The number and size of nodes of Ranvier can vary depending on the type and diameter of the axon. Diseases that damage the myelin sheath, such as multiple sclerosis, can disrupt saltatory conduction and lead to neurological deficits.