Lab 3 (ƒ5) - Somatosensory, Viscerosensory and Spinocerebellar Pathways
Spinal Trigeminal Pathway
The spinal trigeminal pathway,
the cranial homologue of the spinothalamic pathway, mediates crude touch, pain and temperature from the face. Somatosensory information from the face and dura travels via four cranial nerves: the trigeminal (V) nerve, facial (VII) nerve, glossopharyngeal (IX) nerve and the vagus (X) nerve. Recall that some afferent fibers in the facial, glossopharyngeal and vagus nerves carry somatosensory information from the ear (pinna, external auditory meatus, tympanic membrane, and middle ear cavity) and posterior dura. The central processes of the 1° afferent neurons carrying information about simple touch, pain and temperature from the face and dura enter the spinal trigeminal tract and terminate on 2° afferents in the spinal trigeminal nucleus. Most of the 2° afferent axons from the spinal trigeminal nucleus decussate and form the contralateral ventral trigeminothalamic tract (also called the ventral trigeminal lemniscus). The 2° afferent fibers ascend in the ventral trigeminothalamic tract to the thalamus where they terminate on 3° afferents in the ventral posteromedial nucleus (VPM) or intralaminar nuclei of the thalamus. The axons of these 3° afferents ascend in the posterior limb of the internal capsule and terminate in the postcentral gyrus of the parietal lobe (VPM neurons only) or in more diffuse areas of the cerebral cortex (intralaminar nucleus neurons).