The cranial nerve nuclei schematically represented; dorsal view. Motor nuclei in red; sensory in blue. (Trigeminal nerve nuclei are at "V".)
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The sensory trigeminal nerve nucleus is the largest of the cranial nerve nuclei, and extends through the whole of the brainstem, midbrain to medulla.
The nucleus is divided into three parts, from rostral to caudal (top to bottom in humans), the mesencephalic nucleus, the chief sensory or pontine nucleus, and the spinal nucleus. There is also a distinct motor nucleus that is medial to the chief sensory nucleus.
The mesencephalic nucleus is involved with proprioception, that is, the feeling of position of the muscles. Unlike many nuclei within the CNS, the mesencephalic nucleus contains no synapses. Instead, neurons of this nucleus are pseudounipolar cells receiving proprioceptive information from the jaw, and sending projections to the motor trigeminal nucleus to mediate monosynaptic jaw reflexes. (NeuroNames[hier-550])
The chief sensory nucleus receives information about discriminative sensation and light touch as well as conscious proprioception of the jaw. (NeuroNames[hier-552])
