Nerve Fibers, Unmyelinated

**Definition:** 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.

**Tree numbers:** - A08.675.542.756 - A11.671.501.756