High-Yield Neuroanatomy 5e

88 Chapter 10
Motor cortex
UMN
Superior cerebellar peduncle
4th ventricle
Chief sensory nucleus
CN V motor
Motor nucleus CN V
Pons
Medial lemniscus
Corticospinal tract
Lateral pterygoid
LMN
Condyloid process
Figure 10-1 Function and innervation of the lateral pterygoid muscles (LPMs). The LPM receives its innervation from
the trigeminal motor nucleus found in the rostral pons. Bilateral innervation of the LPMs results in protrusion of the mandible
in the midline. The LPMs also depress the mandible. Denervation of one LPM results in deviation of the mandible to
the ipsilateral or weak side. The trigeminal motor nucleus receives bilateral corticonuclear input. CN, cranial nerve; LMN,
lower motor neuron; UMN, upper motor neuron.
III Trigeminothalamic Pathways (Figure 10-2)
A. The anterior trigeminothalamic tract mediates pain and temperature sensation from the face and
oral cavity.
1. First-order neurons are located in the trigeminal (gasserian) ganglion. They give rise to axons
that descend in the spinal tract of trigeminal nerve and synapse with second-order neurons in the
spinal nucleus of trigeminal nerve.
2. Second-order neurons are located in the spinal trigeminal nucleus. They give rise to decussating
axons that terminate in the contralateral ventral posteromedial (VPM) nucleus of the thalamus.
3. Third-order neurons are located in the VPM nucleus of the thalamus. They project through the
posterior limb of the internal capsule to the face area of the somatosensory cortex (Brodmann areas
3, 1, and 2).
B. The posterior trigeminothalamic tract mediates tactile discrimination and pressure sensation from
the face and oral cavity. It receives input from Meissner and Pacinian corpuscles.