Sensory innervation of the face

• Supplied by branches of CN V (trigeminal nerve)

CN V1 (ophthalmic nerve)

• Upper eyelid
• Cornea
• Conjunctiva

CN V2 (maxillary nerve)

• Skin of the lower eyelid
• Skin over the maxilla

CN V3 (mandibular nerve)

• Skin over mandible and TMJ, except over angle of mandible

Corneal (blink) reflex

• Involuntary blinking of the eyelids elicited by stimulation of the cornea
• Protective function - protects the eyes from foreign bodies and bright lights
• Sensory (afferent) limb:
  • Action potentials conducted from cornea via CN V1 branches
  • To trigenimal ganglion, then along CN V to pons
• Central CNS connections between CN V and CN VII
• Motor (efferent) limb:
  • Action potentials conducted via CN VII to eyelid part of orbicularis oculi

Autonomic reflexes of the eye

• Sympathetic - eyes open wider to get more light into eyes, may help focus on far objects, emotional lacrimation
• Parasympathetic - get less light into into eyes (to protect the retina from bright light or when asleep), focus on near objects, reflex lacrimation (to wash away stimulant foreign body and clean the cornea)

Wide eye opening of fight or flight

• Levator palpebrae superioris contains skeletal muscle (voluntary - CN III) plus smooth muscle (Mueller's muscle) (involuntary - sympathetic innervation)

• Postsynaptic sympathetic fibres travel via:
  • Superior cervical sympathetic ganglion
  • Internal carotid nerve
  • Internal carotid plexus
  • Axons carried on ophthalmic artery and on its branches to orbital structures

Pupillary constriction and dilation

Pupillary constriction