Cranial Nerves

Question 1

Which cranial nerves are not true nerves?

Answer 1

CN 1 & 11

they are fiber tracts

Question 2

CN 1

Answer 2

olfactory (smell)

• odor –> sensory receptors –> detected by olfactory bulb –> travel through olfactory tract –> terminate in anterior perforated substance –> intimate connections with entorhinal cortex, amygdala, hippocampus, and other parts of the limbic system

Question 3

What parts of the brain are stimulated when you smell something?

Answer 3

• entorhinal cortex (memory, navigation, perception of time)
• amygdala (emotions; fear)
• hippocampus (memories)
• other parts of the limbic system

Question 4

anosmia

Answer 4

partial or full loss of smell
- colds, rhinitis, tumors

Question 5

hyperosmia

Answer 5

overwhelming sensitivity to smells
- hysterics, cocaine addicts

Question 6

parosmia

Answer 6

distorted sense of smell
- olfactory hallucinations, hysterics, seizures, schizophrenia, uncinate gyrus lesions

Question 7

cacosmia

Answer 7

unpleasant odors
- decomposition of tissue

Question 8

CN II

Answer 8

optic

• visual acuity, visual fields, fundi exam

Question 9

How does light get processed in the eyes?

Answer 9

eyeball focuses light –> stimulates retina –> signals transmitted via optic nerve, chiasm, and tract to lateral geniculate nucleus (thalamus) –> impulses travel via optic radiations –> termination in the primary visual cortex (calcarine)

Question 10

Lesion at the right optic nerve

Answer 10

anopsia of the right eye

• full right sided blindness

Question 11

Lesion at the optic chiasm

Answer 11

bitemporal hemianopia

• temporal fields affected –> can’t cross chiasm

Question 12

Lesion at right optic tract (lateral geniculate)

Answer 12

right homonymous hemianopia

• temporal retina of L eye + nasal visual field of R eye affected

Question 13

Name all 12 cranial nerves

Answer 13

I - Olfactory
II - Optic
III - Oculomotor
IV - Trochlear
V - Trigeminal
VI - Abducens
VII - Facial
VIII - Vestibulocochlear
IX - Glossopharyngeal
X - Vagus
XI - Accessory
XII - Hypoglossal

Question 14

Three branches of the trigeminal nerve

Answer 14

V1 = ophthalmic
V2 = maxillary
V3 = mandibular

Question 15

CN III

Answer 15

oculomotor

• pupil diameter/response, accommodation
• “all the rest are 3”
• injury - dilated pupil + ptosis (fixed and dilated)

Question 16

CN IV

Answer 16

trochlear

• SO4

Question 17

CN V

Answer 17

trigeminal

• masseter muscle
• corneal reflex

Question 18

CN VI

Answer 18

abducens

• LR6

Question 19

CN VII

Answer 19

facial

• asymmetry of the face
• CVA or Bell’s Palsy
• injury = facial droop, dry eyes, dry mouth

Question 20

Bell’s Palsy vs. CVA

Answer 20

Bell’s Palsy = unilateral facial paralysis
CVA = forehead can still wrinkle, the rest paralyzed

Question 21

CN VIII

Answer 21

auditory

• whisper test, Weber, Rinne
• 256 Hz tuning fork

Question 22

CN IX

Answer 22

glossopharyngeal

• voice, gag reflex, UVULA DEVIATION, sensory posterior 1/3 tongue, auditory tube, pharynx

Question 23

CN X

Answer 23

vagus

• termed “wanderer” because it is the LONGEST cranial nerve
• gag reflex, voice, uvula deviation, sensory/motor for larynx/pharynx
• palatoglossus (tongue control)

Question 24

CN XI

Answer 24

accessory

• muscles of larynx + pharynx
• muscles of traps + SCM
• shrug shoulders, push head laterally against hand

Question 25

CN XII

Answer 25

hypoglossal

• controls 3 of 4 tongue’s extrinsic muscles –> genioglossus, styloglossus, hyoglossus
• TONGUE DEVIATION, atrophy, fasiculations

Question 26

For all the cranial nerves, which are sensory, motor, or both?

Answer 26

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Question 27

What tests can you perform to test CN II?

Answer 27

Visual acuity, visual fields, fundoscopic exam

Question 28

What tests can you perform to test CN III?

Answer 28

Pupillary reaction, diameter, and accommodation