Talk about myelinated nerve fibers

They are mono-axonal, that is to say constituted by a single myelinated axon, associated with a sequence of Schwann cells. Each Schwann cell extends over a segment of the nerve fiber called internode, which is the space between 2 neighboring Ranvier constrictions (or nodes). The constrictions of Ranvier thus represent the separation between a Schwann cell and its myelin on the one hand, and the neighboring Schwann cell and its myelin on the other hand. In optic microscopy, the myelin sheath has the shape of a tube interrupted, at regular intervals, by the nodes of Ranvier. A single Schwann cell provides formation and covers with myelin each internode.