ABSTRACT
The craniofacial region is richly supplied with sensory fibers that innervate the temporo mandibular joint, periodontal region, oral mucosa, tongue muscles, and craniomandibular muscles. The sensory input depends predominantly on the type of ending of the sensory fiber, which responds to specific stimuli and then transduces that stimulus into an electrical signal generated as an action potential that proceeds along the sensory fiber to the central nervous system. Sensory fibers vary in size with a wide range of sizes represented in fibers with a myelin sheath, and the smallest sensory fibers having no myelin sheath. The largest myeli nated sensory fibers have receptors that respond to changes in length, as in the muscle spindles of the jaw-closing muscles, or to changes in tension. The medium size sensory fibers are excited by delicate touch or pressure and divide into those that respond to a constant stimulus to accurately indicate the length of time a stimulus remains and to those receptors which are only excited when the stimulus is initially placed or removed. The smallest myelinated fibers respond to changes in temperature of the immediate tissue around them and also to tissue damage in which specific chemicals excite these small myelinated fibers and the subject perceives pain. The unmyelinated fibers are the smallest of all the sensory fibers and include some that respond to changes in temperature, a few that respond to mechanical stimuli, and many which respond to chemicals that induce the sensation of pain.
