Ranvier

Ranvier most commonly refers to Louis-Antoine Ranvier, a 19th-century French anatomist and histologist (1830–1906) who described gaps in the myelin sheath of peripheral nerve fibers. The term is also used for the gaps themselves, known as nodes of Ranvier, which are regular interruptions in the myelin sheath along a myelinated axon.

Nodes of Ranvier are short, regularly spaced gaps in the myelin sheath between adjacent glial segments. They expose the axonal membrane to the extracellular environment. In the peripheral nervous system these gaps lie between Schwann cell segments; in the central nervous system they occur between myelin produced by oligodendrocytes. Typical node length is on the order of about one micrometer.

The nodes are rich in voltage-gated sodium channels and other nodal proteins. They serve as sites for action potential regeneration, enabling saltatory conduction in which the electrical signal is effectively helped along from node to node. Myelin insulation increases membrane resistance and reduces capacitance, allowing rapid signal transmission with fewer ionic exchanges. The precise arrangement of nodes, paranodes, and internodes influences conduction velocity and signal fidelity.

Louis-Antoine Ranvier’s observations contributed to the understanding of fast nerve signaling and the functional importance of myelination. The concept remains central in neurophysiology and is relevant to studies of demyelinating diseases and nerve repair, where nodal structure and function are affected.