TRIGEMINAL MOTOR FUNCTIONS

A. Structures Innervated

1. Muscles of mastication (extrafusal fibers), via the mandibular branch

2. Intrafusal fibers of muscles of mastication (mandibular branch) and extraoccular eye muscles (ophthalmic branch)

3. Other: tensor tympani (hearing sensitivity); tensor veli palatini (open Eustachian tube); mylohyoid, digastric (swallowing)

B. Pathway

1. Cell bodies: motor nucleus of c.n. V

2. Input

a. descending fibers involved in voluntary and involuntary motor control
b. afferent fibers from mastication muscle spindle proprioceptors via the mesencephalic nucleus

C. Reflexes

1. Jaw jerk reflex: stretch of jaw closing muscles causes reflex contraction of muscles that were stretched (myotatic reflex) -- contributes to tone and posture

2. Jaw flexion reflex: noxious oral cavity stimuli inhibit jaw closing muscles and facilitate contraction of jaw opening muscles (protective)