21 - Trigeminal Nerve

Abstract

The motor root of the trigeminal nerve (CN V) nerve enters the mandibular division to supply the four muscles of mastication and the anterior belly of digastric, mylohyoid, tensor tympani, and tensor veli palatini. Automatic control is by the supratrigeminal nucleus, and voluntary control is from the motor cortex (mainly contralaterally). The trigeminal (gasserian) ganglion (contains unipolar cells) sends peripheral processes into all three divisions and provides sensory endings in the face, oronasal mucous membranes, teeth, meninges, and intracranial blood vessels. Central processes synapse in the pontine (principal sensory) and spinal nuclei. Peripheral processes proprioceptive to masticatory muscles and periodontal ligaments belong to the unipolar-celled mesencephalic nucleus. The main target of the central processes of these cells is the supratrigeminal nucleus, which is the masticatory generator. The pontine nucleus processes tactile information from the face and oronasal mucous membranes. The spinal nucleus receives nociceptive signals from the entire trigeminal sensory field, from the oropharynx via the glossopharyngeal, from the laryngopharynx and larynx via the vagus, and from the posterior rami of upper cervical nerves. The pontine and spinal nuclei project fibres into the reticular formation (serving arousal) and to the contralateral thalamus via the trigeminothalamic tract.