19. Cranial Nerves

Question 1

Characteristics of the cranial nerves

Answer 1

12 pairs numbered anterior (rostral) to posterior (caudal)
Most originate from brainstem except first 2 pairs from prosencephalon
All innervate only structures in the head except for CN X vagus nerve
Functions are Sensory, motor, or both

Question 2

CN I- olfactory nerve

Answer 2

Function: smell (special sensory)
Pathway: cribriform plate of ethmoid bone
Neurons synapse in olfactory bulbs

Question 3

CN II- optic nerve

Answer 3

Function: vision (special sensory) (carries visual info from retina)
Pathway: optic canal
Optic chasm allows for some visual info to cross to opposite sides of the brain

Question 4

Extra-ocular eye muscles

Answer 4

6 extrinsic muscles (4 rectus and 2 oblique)
Control movements of the eye
Originate from tendinous ring in posterior orbit

Question 5

Types and movements of extrinsic eye muscles

Answer 5

Rectus muscles:
Superior rectus (up and in)
Inferior rectus (down and in)
Medial rectus (in/adduct)
Lateral rectus (out/abduct)
Oblique muscles:
Superior oblique (down and out)
Inferior oblique (up and out)

Question 6

Intrinsic muscles of the eye

Answer 6

Smooth muscle, controlled by autonomic NS
Include muscles of iris and ciliary muscle

Question 7

Function and types of muscles of iris

Answer 7

Controls amount of light passing into eye
Include sphincter pupillae muscle and dilator pupillae muscle

Question 8

Function of ciliary muscle

Answer 8

Controls shape of lens to focus on objects near or far

Question 9

CN III- oculomotor nerve

Answer 9

Functions:
Motor to superior rectus, medial rectus, inferior rectus, and inferior oblique
Parasympathetics to muscles of pupil and lens (constrict pupil and thicken lens)
Pathway: superior orbital fissure to orbit

Question 10

CN IV- trochlear nerve

Answer 10

Function: motor to superior oblique muscle (muscle that travels through trochlea)
Pathway: superior orbital fissure to orbit

Question 11

Divisions of CN V- trigeminal nerve

Answer 11

3 divisions
Ophthalmic division (V1)
Maxillary division (V2)
Mandibular division (V3)

Question 12

Function and pathway of opthalmic division (V1) of trigeminal nerve

Answer 12

Function: sensation from skin of face, cornea, paranasal sinuses
Pathway: superior orbital fissure

Question 13

Function and pathway of maxillary division (V2) of trigeminal nerve

Answer 13

Function: sensation from skin of face, upper teeth, paranasal sinuses
Pathway: foramen rotundum

Question 14

Function and pathway of mandibular division (V3) of trigeminal nerve

Answer 14

Function:
sensation from skin of face, lower teeth, tongue
Somatic motor to muscles of mastication
Pathway: foramen ovale

Question 15

CN VI- abducens nerve

Answer 15

Function: motor to lateral rectus muscle of eye (abducts eye)
Pathway: superior orbital fissure to orbit

Question 16

Types and innervation of salivary glands

Answer 16

3 types: parotid, submandibular, and sublingual
Innervated by cranial nerves

Question 17

CN VII- facial nerve

Answer 17

Function:
Somatic motor to muscles of facial expression
Visceral motor to submandibular & sublingual salivary glands
Visceral motor to lacrimal gland
Taste from tongue
Pathway: internal acoustic meatus

Question 18

CN VIII- vestibulocochlear nerve

Answer 18

Function: special sensory for hearing and balance
Pathway: internal acoustic meatus

Question 19

CN IX- glossopharyngeal nerve

Answer 19

Function:
Somatic motor to stylopharyngeus
Taste from posterior tongue
Sensation from posterior tongue
Visceral motor to parotid salivary gland
Pathway: jugular foramen

Question 20

Sensation from tongue

Answer 20

Posterior 1/3- general sensation and taste via glossopharyngeal nerve (CN IX)
Anterior 2/3- general sensation from mandibular division of trigeminal nerve (V3) and taste from facial nerve (CN VII)

Question 21

CN X- vagus nerve

Answer 21

Function:
Somatic motor to muscles of pharynx and larynx (swallowing and speaking)
Visceral motor to heart, bronchi, muscles of digestive tract
Sensation from larynx and pharynx
Pathway: jugular foramen

Question 22

CN XI- accessory nerve

Answer 22

Function: somatic motor to sternocleidomastoid and trapezius muscles
Pathway: jugular foramen

Question 23

CN XII- hypoglossal nerve

Answer 23

Function: somatic motor to muscles of the tongue
Pathway: hypoglossal canal