Which cranial nerve is primarily associated with jaw clenching?

• A. Oculomotor nerve (CN III)
• B. Trochlear nerve (CN IV)
• C. Trigeminal nerve (CN V)
• D. Vagus nerve (CN X)

Answer: (C)

Jaw clenching is a motor action carried out by the muscles of mastication—the masseter, temporalis, and the pterygoids. These muscles receive their motor supply from the trigeminal nerve, specifically its mandibular division, which contains the motor neurons that drive jaw closure. The trigeminal nerve is also responsible for jaw proprioception via its sensory pathways, helping regulate bite force and jaw position.

The other nerves listed don’t control these muscles: the oculomotor and trochlear nerves govern eye movements, not the jaw, while the vagus nerve controls most pharyngeal, laryngeal, and autonomic functions rather than the muscles used to bite or clench.