The sensorimotor integration of the muscles of the lower face depends on which two cranial nerves?

• A. Accessory and hypoglossal
• B. Trigeminal and facial
• C. Vagus and glossopharyngeal
• D. Phrenic and facial

Answer: (B)

Understanding how the lower face moves and feels together relies on two cranial nerves working in concert. The facial nerve provides the motor signals that actually move the muscles of facial expression in the lower face, shaping movements of the lips and lower cheek. For integration, the brain also needs sensory feedback from the face, which comes from the trigeminal nerve, supplying facial sensation and carrying proprioceptive information about facial muscles. This combination—motor output from the facial nerve plus sensory feedback from the trigeminal nerve—lets the brain coordinate precise, coordinated movements of the lower face. The other nerve pairs don’t provide this same combination of motor control for the lower face and sensory input from the face.