cranial nerves (theory)

Question 1

how many cranial nerves are there?

Answer 1

there are 12 cranial nerve pairs

1. olfactory
2. optic
3. oculomotor
4. trochlear
5. trigeminal
6. abducens
7. facial
8. vestibulocochlear
9. glossopharyngeal
10. vagus
11. accessory
12. hypoglossal

Question 2

CN I

Answer 2

the olfactory nerve

1. helps with smell
2. ends at the olfactory bulbs

Question 3

olfactory nerve pathway

Answer 3

the olfactory nerve fibers (hair cells) of the nerve receive stimuli, this stimulates the olfactory nerve which runs down the olfactory tract

this eventually ends in the insula (olfactory cortex)

Question 4

CN II

Answer 4

the optic nerve

1. senses visual stimuli (purely sensory)
2. first goes to the diencephalon
3. then goes to the occipital lobe

recall that pretty much all sensory input goes through the thalamus

Question 5

what is the relay of the optic nerve in the thalamus (LGN)

Answer 5

lateral geniculate nucleus

Question 6

why are the eyes cup shaped?

Answer 6

they are cup shaped bc they contain nasal and temporal fibers

these fibers are named by their spatial position

the nasal fibers see lateral vision
the temporal fibers see medial vision

Question 7

what fibers of the retina cross?

Answer 7

the nasal fibers cross at the optic chiasm

Question 8

CN III

Answer 8

the oculomotor nerve

1. this controls the extra and intra-ocular eye muscles EXCEPT the lateral rectus and the superior oblique
2. ends at the extra-ocular eye muscles

Question 9

CN IV

Answer 9

trochlear nerve

1. supplies the superior oblique
2. ends at the superior oblique

Question 10

CN V

Answer 10

trigeminal nerve

1. supplies muscles of mastication
2. provides facial sensation along its 3 branches
3. the ophthalamic and maxillary branches end at the pons
4. mandibular branch ends at the mandibular muscles

Question 11

what are the 3 branches of the trigeminal nerve?

Answer 11

1. ophthalamic branch
2. maxillary branch
3. mandibular branch

Question 12

CN VI

Answer 12

abducens nerve

1. supplies the lateral rectus
2. ends at the lateral rectus

Question 13

CN VII

Answer 13

facial nerve

1. supplies the facial muscles
2. provides sensation for the face and taste

Question 14

where does the sensory part of the facial nerve end?

Answer 14

the pons

Question 15

where does the motor part of the facial nerve end? (think literally)

Answer 15

the face muscles

Question 16

CN VIII

Answer 16

vestibulocochlear nerve

1. purely sensory, it provides balance and hearing
2. ends at the pons

Question 17

CN IX

Answer 17

glossopharyngeal nerve

1. it provides sensation and motor control BUT it does NOT move the tongue
2. senses tongue pain
3. controls pharyngeal muscles for swallowing
4. also supplies the posterior 1/3 of the tongue

Question 18

where does the glossopharyngeal nerve (CN IX) end?

Answer 18

1. sensory info = medulla
2. visceral motor = parotid salivary gland
3. somatic motor = pharyngeal muscles

Question 19

carotid body, sinus and artery (prof’s notes)

Answer 19

the baroreceptors monitor the blood pressure and link with the glossopharyngeal and vagus nerve

Question 20

CN X

Answer 20

the vagus nerve

*the only cranial nerve to leave the head and neck

*also produces ACh

*the parasympathetic nerve

1. sensory info from the organs
2. sensory info to the organs

Question 21

where do the parts of the vagus nerve end?

Answer 21

1. sensory = autonomic centers of the medulla
2. somatic = muscles of the palate and pharynx
3. visceral motor = respiratory, cardio, digestive organs

Question 22

CN XI

Answer 22

accessory nerve

1. controls the sternocleidomastoid and trapezius
2. the external branch ends at the sternocleidomastoid and trapezius

Question 23

CN XII

Answer 23

hypoglossal nerve

1. controls tongue movement
2. ends at the tongue muscles

Question 24

mnemonic aid for the cranial nerves

Answer 24

oh –> olfactory
once –> optic
one –> oculomotor
takes –> trochlear
the –> trigeminal
anatomy –> abducens
final –> facial
very –> vestibulocochlear
good –> glossopharyngeal
vacations –> vagus
are –> accessory
heavenly –> hypoglossal

Question 25

what is the positioning of the accessory and hypoglossal nerves?

Answer 25

since the accessory nerve supplies muscles below the tongue, the accessory nerve sits below the hypoglossal nerve even though it is CN XI