<prompt> Fibres most sensitive to local anesthesia areABCNone  <response>: Group C nerve fibers are one of three classes of nerve fiber in the central nervous system CNS and peripheral nervous system PNS. The C group fibers are unmyelinated and have a small diameter and low conduction velocity, whereas Groups A and B are myelinated. Group C fibers include postganglionic fibers in the autonomic nervous system ANS, and nerve fibers at the dorsal roots IV fiber. These fibers carry sensory information C fibers and A-d are sensitive to local anesthesia Ref guyton and hall textbook of medical physiology Edition 12 pg 701 Group C nerve fiber C fiber not labeled, but substantia gelatinosa of Rolando is Rexed lamina II, labeled at upper left. 