A class of nerve fibers as defined by their nerve sheath arrangement. The AXONS of the unmyelinated nerve fibers are small in diameter and usually several are surrounded by a single MYELIN SHEATH. They conduct low-velocity impulses, and represent the majority of peripheral sensory and autonomic fibers, but are also found in the BRAIN and SPINAL CORD.

Type C fibers are peripheral unmyelinated nerve fibers in which several AXONS are surrounded by a single Schwann cell (SCHWANN CELLS). They constitute more than half of the peripheral sensory nerve fibers as well as all the postganglionic autonomic fibers.

Synonyms: Unmyelinated Nerve Fiber, C Fiber, C Fibers, Nerve Fiber, Unmyelinated, Nerve Fibers, Unmyelinated, Unmyelinated Nerve Fibers