What is Which of the following nerves serves as an afferent in mediation of corneal reflex? and explain in detail?
Ans. c (Nasociliary nerve) (Ref. BDC Vol. 3. - 4th/ pg. 117-8)CORNEAL REFLEX# In the corneal reflex, both eyes normally blink upon touching either cornea.# If neither eye blinks on touching the right cornea and both eyes blink on touching the left cornea, cranial nerve CN5 is likely to be affected.# Corneal reflex involves the reflex activation of the ophthalmic division of the sensory component of cranial nerve V in response to touching of the cornea and the motor division of the facial nerve, which produces the motor component (i.e., the blinking response). The sensory component of cranial nerve V is classified as a general somatic afferent fiber and the somatic motor component of cranial nerve VII is classified as a special visceral efferent fiber.Cranial nerve reflexAfferentEfferentCornealV1 ophthalmic (nasociliary branch)VII (temporal branch: orbicularis oculi)LacrimationV1VIIJaw jerkV3(sensory--muscle spindle from masseter)V3 (motor--masseter)PupillaryIIIIIGagIXIX, XThe Ophthalmic Nerve I first division of the trigeminal1It is a sensory nerve that supplies branches to the cornea, ciliary body, and iris; to the lacrimal gland and conjunctiva; to the part of the mucous membrane of the nasal cavity; and to the skin of the eyelids, eyebrow, forehead, and nose. It is the smallest of the three divisions of the trigeminal, and just before entering the orbit, through the superior orbital fissure, it divides into three branches -# Lacrimal# Frontal, and# Nasociliary.SENSORY INNERVATIONNasociliary Nerve# The nasociliary nerve passes above and medial to eye before giving off following branches to the nose and eye:(1) Branches to ciliary ganglion(2) Anterior ethmoidal(3) Posterior ethmoidal(4) Infratrochlear(5) 2-3 long ciliary nerves# The nasal component is made of the ethmoidal and nasal nerves that carry sensation from the roof of the nasal cavity, the skin of the nose, and the sphenoid and ethmoid sinuses.# The ciliary component is made of the long and short ciliary nerves that carry sensation from the eye and cornea.Lacrimal Nerve# The Lacrimal Nerve is the smallest of the three branches of the ophthalmic.# The lacrimal nerve passes above and lateral to the eye.# It carries sensation from the lateral part of the upper eyelid.Frontal Nerve# The frontal nerve passes over the eye and divides into(1) Supratrochlear and(2) Supraorbital nerves.# The supraorbital nerve exits the orbit through the supraorbital notch (foramen) and carries sensation from the skin of the forehead that lies lateral to the area served by the supratrochlear nerve.# The supraorbital nerve also carries sensation from the frontal sinuses.