Cranial nerve reflexes

Question 1

Pupillary light reflex

Answer 1

1. Shine bright light in one eye
2. Optic nerve CN II
3. Synapse with pretectal neurons in pretectal area
4. Synapse with CN III in Edinger-Westphal nuclei
5. CN III parasympathetic neurons to ciliary ganglion
6. Postganglionic neurons innervate constrictor pupillae

Question 2

Corneal blink reflex

Answer 2

1. Foreign particle on the eye
2. Opthalmic division of Trigeminal nerve CN V
3. Synapse in spinal and chief sensory nuclei
4. Interneurons synapse bilaterally with facial nerve CN VII in facial nucleus
5. Facial nerve innervates orbicularis oculi

Question 3

Accommodation reflex

Answer 3

1. CN II afferents to bilateral LGN
2. Primary visual cortex
3. Visual association area
4. Pretectal area
5. Synapses with CN III in Oculomotor and Edinger-Westphal nuclei
6. CN III somatic fibres innervate medial rectus
7. CN III parasympathetic fibres innervate ciliary muscle and constrictor pupillae

Question 4

Vestibulo-ocular reflex

Answer 4

1. Movement of the head
2. Vestibular apparatus detects head movement
3. Vestibular nerve CN VIII
4. Ipsilateral vestibular nerve
5. Projects to contralateral abducens nucleus
6. Projects to ipsilateral CN VI to lateral rectus and contralateral oculomotor nucleus via MLF
7. CN III to medial rectus