Nodes of Ranvier
gaps in the myelin sheath
The nodes of Ranvier are gaps in the myelin sheath surrounding axons in nervous tissue. These unmyelinated regions are approximately 1 micrometer wide and serve to facilitate the propagation of action potentials along the axon.
At the nodes of Ranvier, the axonal membrane is exposed to extracellular fluid, allowing for the exchange of ions necessary for the depolarization and repolarization of the membrane. In myelinated axons, the myelin sheath insulates the underlying axon, preventing ion exchange and slowing the spread of the action potential. However, at the nodes of Ranvier, the action potential can be efficiently regenerated, as the ion channels necessary for depolarization are concentrated at these locations.
Therefore, the nodes of Ranvier play an important role in maintaining the speed and efficiency of nerve impulse transmission. Without these regular interruptions in the myelin sheath, conduction velocity of nerve impulses would be significantly slowed down, resulting in impaired nervous system function.
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