In the jaw jerk (masseteric) reflex, both the afferent and efferent limbs are carried by the same nerve. Which nucleus houses the cell bodies of the primary sensory neurons responsible for the afferent limb?

• A Spinal trigeminal nucleus
• B Main (chief) sensory nucleus of the trigeminal nerve
• C Mesencephalic nucleus of the trigeminal nerve ✓
• D Motor nucleus of the trigeminal nerve

Explanation

Muscle spindles in the masticatory muscles send proprioceptive fibres through the mandibular division to cell bodies in the mesencephalic nucleus, a unique arrangement because these are first order sensory neurons located within the CNS rather than in a peripheral ganglion. These neurons project directly to the trigeminal motor nucleus, forming a monosynaptic reflex. The main sensory nucleus handles discriminative touch of the face, and the spinal nucleus handles pain and temperature.

Reference: Snell's Clinical Neuroanatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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