Final answer:
The GSA fibers of the trigeminal nerve transmit sensory information from the face and enter the brain stem at the pons level. The chief nucleus in the pons processes light touch, while the spinal trigeminal nucleus in the medulla processes pain and temperature sensations.
Step-by-step explanation:
The GSA fibers (General Somatic Afferent fibers) of the trigeminal nerve are primarily responsible for transmitting sensory information from the face to the brain. These fibers are part of the trigeminal system, which can be thought of as the equivalent of the ascending spinal cord systems of the dorsal column and the spinothalamic pathways. Sensory discrimination is an important function of the GSA fibers of the trigeminal nerve, which is tested by using a cotton-tipped applicator to deliver a touch stimulus (relayed by the chief nucleus in the pons) or a painful stimulus (relayed by the spinal trigeminal nucleus in the medulla).The chief nucleus in the pons processes information about light touch and proprioceptive information, whereas the spinal trigeminal nucleus in the medulla processes information about crude touch, pain, and temperature. Thus, the GSA fibers associated with the trigeminal nerve transmit sensory information to synapses across multiple nuclei in the brain stem, specifically entering the brain stem at the level of the pons but ultimately synapsing in areas including the pons and the medulla.