Nervous System: Cranial Nerves

Question 1

CN I 
(name, function)

Answer 1

Olfactory nerve

• sensory: smell
• olfactory bulb/ tract (primary olfactory cortex)
• only sensory to bypass thalamus into temporal lobe

Question 2

CN I (damage/ disease)

Answer 2

Olfactory nerve

• hyposmia (reduced smell)
• anosmia (no smell)

Question 3

CN II (name, function)

Answer 3

Optic nerve

• sensory: vision
• optic tract > thalamus > calcarine sulcus (primary visual cortex)
• inverted + reversed – brain reverts image

Question 4

CN II (damage)

Answer 4

Optic nerve

- visual field effects (dependent on which axons are compromised)

Question 5

CN III (name, function)

Answer 5

Oculomotor nerve

• motor: extra-ocular > moves eye within orbit, elevates upper lid
• PS: pupillary constriction, change shape of lens (ciliary ganglion, mm.)

Question 6

CN III (damage/ disease)

Answer 6

Oculomotor nerve

• pupillary dilation (no PS)
• ophthalmoplegia (weakened/ paralyzed eye movements)

Question 7

CN IV (name, function)

Answer 7

Trochlear nerve

• motor: superior oblique –> moves eyeball (abducts, depresses, internally rotates)
• smallest cranial nerve
• only CN to come from posterior of brainstem

Question 8

CN IV (damage)

Answer 8

• isolated damage = uncommon (well protected, lies along dura mater)

Question 9

CN V (general/ branch names - individual functions)

Answer 9

Trigeminal nerve (main sensory for face; PS uses to tract)

i) OPHTHALMIC nerve
- supraorbital nn.
- ciliary ganglion (PS to eye)
- sensory: eye[ball], nasal cavity, forehead
ii) MAXILLARY nerve
- infraorbital nn
- sensory: nasal cavity (clogging=pain), upper maxillary, cheek bone
iii) MANDIBULAR nerve
- lingual nn, mental nn,
- S: ant. 2/3 tongue, mandible, proprioception of mastication
- M: muscles of mastication

Question 10

CN V (disease)

Answer 10

Trigeminal nerve

- trigeminal neuralgia (Tic Douloureux) –> mainly V2/V3 –> extremely painful