internodal segment internodal segment an internodal segment (or internode) is the portion of a nerve fiber between two nodes of ranvier. the neurolemma or primitive sheath is not interrupted at the nodes, but passes over them as a continuous membrane. internodal segmentdiagram of longitudinal sections of medullated nerve fibers.medullated nerve fibers stained with silver nitrate.detailspart ofaxon of nerve fibersystemnervous systemidentifierslatinsegmentum internodalethh2.00.06.2.03028 anatomical terms of microanatomy