Where are the nuclei of the trigeminal nerve (CN V) located?

• A. In the CNS & in ganglia outside the CNS
• B. In the CNS only
• C. In the ganglia outside the CNS only
• D. In the spinal cord

Answer: (A)

Nerves of CN V are organized with centers in the brainstem and peripheral cell bodies outside the CNS. The nuclei that process CN V functions reside in the brainstem (the CNS): the motor nucleus in the pons controls the muscles of mastication, and the sensory nuclei (principal sensory in the pons, spinal trigeminal extending caudally, and the mesencephalic nucleus for proprioception) receive and relay sensory information. The cell bodies of the first-order sensory neurons, however, sit in the trigeminal (semilunar) ganglion, a peripheral ganglion outside the CNS. From there, central processes enter the brainstem to synapse on those nuclei, while motor fibers originate from the motor nucleus within the brainstem. So CN V has nuclei in the CNS and sensory neuron cell bodies in ganglia outside the CNS, which is why this answer is the best fit.