Mod 4: Lecture 2: Overview of Cranial Nerves

Question 1

Brain Stem

Answer 1

• Midbrain
• Pons
• Medulla

Question 2

Mnemonic for the 12 pairs of Cranial Nerves

Answer 2

• Oh Once One Takes The Anatomy Final, Very Good Vacations Are Heavenly.

Question 3

Cranial Nerves: I - IV

Answer 3

I. Olfactory
II. Optic
III. Oculomotor
IV. Trochlear

Question 4

Cranial Nerves: V - VIII

Answer 4

V. Trigeminal
VI. Abducens
VII. Facial
VIII. Vestibulocochlear

Question 5

Cranial Nerves: IX - XII

Answer 5

IX. Glossopharyngeal
X. Vagus
XI. (Spinal) Accessory
XII. Hypoglossal

Question 6

Cranial Nerves Originating in the Diencephalon-Brainstem (Can’t read slide, see video)

Answer 6

I. Olfactory

II. Optic

Question 7

Cranial Nerves Originating in the Midbrain

Answer 7

III. Oculomotor

IV. Trochlear

Question 8

Cranial Nerves Originating in the Pons

Answer 8

V. Trigeminal
VI. Abducens
VII. Facial
VIII. Vestibulocochlear

Question 9

Cranial Nerves Originating in the Medulla

Answer 9

IX. Glossopharyngeal
X. Vagus
XI. Accessory
XIII. Hypoglossal

Question 10

Cranial Nerves are part of the __1__ nervous system and pass through the skull via __2__ or __3__.

Answer 10

1. peripheral
2. foramina
3. fissures

Question 11

Cranial Nerve Classification

Answer 11

• Sensory: vision, smell, touch
• Motor: somatic and visceral
• Both

Question 12

CN I. Olfactory Nerve

Answer 12

• sensory
• olfactory bulb is on the cribriform plate
• fibers of olfactory nerves extend down into the nasal passages by the nasal conchae

Question 13

CN II: Optic

Answer 13

• sensory
• info from the right and left visual field goes to both eyes and both optic nerves
• at the optic chiasma, the right and left optic nerves cross
• — info from the right visual field from both eyes goes to the left brain
• — same for info from the left visual field

Question 14

III. Occulomotor

Answer 14

• motor
• innervates the elevator of the upper eyelid
• — levator palpebrae superioris
• innervates 4 of 6 muscles responsible for movement of the eyeball
• — rectus superior, rectus inferior, rectus medial and inferior oblique
• — does not innervate the superior oblique or the rectus lateral
• parasympathetic motor fibers to the sphincter muscle of the iris
• — pupil constriction

Question 15

Isolated movements of the eyeball

Answer 15

• elevation
• depression
• adduction: toward midline/nose
• abduction: away from midline
• internal/medial rotation
• — intorsion
• — 12 o’clock position moves clockwise (toward nose)

Question 16

Direction of pull and action of the extraocular eye muscles if they were to contract in isolation….

1. Superior rectus
2. Inferior Rectus
3. Medial Rectus
4. Lateral Rectus

Answer 16

1. • Pulls upward
     - elevation
     - — you look up
2. • pulls downward
     - depression
     - — you look down
3. • pulls inward to the nose
     - adduction
     - — when both do it, you go cross eyed
4. • pulls outward, to the lateral side, away from the body
     - abduction
     - — you glance sideways

Question 17

Eye Muscles: Superior Oblique

1. Attachments
2. Action
3. Innervation

Answer 17

1. • posterior and superior to the horizontal axis
2. • rotate clockwise, from the top to the nose
     - intorsion (internal/medial rotation)
     - depression
     - — you roll your eyes
     - — bc of attachment, it lifts up the back of the globe, therefore the rest turns down (depresses)
3. IV. Trochlear

Question 18

Eye Muscles: Inferior Oblique

1. Attachments
2. Action
3. Innervation

Answer 18

1. • posterior and inferior to the horizontal axis
2. • rotate counterclockwise, from the bottom to the nose
     - extorsion (external/lateral rotation)
     - elevation
     - — you roll your eyes
     - — bc of attachment, it pulls down the back of the globe, and therefore pushes the rest or the eye up (elevates)
3. III. Occulomotor

Question 19

Innervation of the lateral rectus

Answer 19

• CN VI. Abducens

- all other rectuses are CN III. Occulomotor

Question 20

Pupillary Light Reflex

Answer 20

• automatic constriction of pupils upon exposure to bright light
• light entering the eye travels along the optic nerve to the midbrain to cause pupillary constriction
• — through the visceral motor and short component of the occulomotor

Question 21

Occulomotor Palsy

Answer 21

• ptosis, pupil dilation

- see video

Question 22

Abducens Lesion

Answer 22

• adjacent nerve injury
• abducens goes to the lateral rectus
• — abducens stops working, eye (pupil/iris) falls to one side instead of being in the middle
• see video

Question 23

IV. Trochlear

VI. Abducens

Answer 23

IV. - motor
- superior oblique of the eye
VI. - motor
- lateral rectus of the eye

Question 24

V. Trigeminal

Answer 24

• mixed
• V1. Ophthalmic: above eyes
• V2. Maxillary: upper lip and cheek
• V3. Mandibular:
• — motor to muscles of mastication
• — sensory branches to lower jaw and side of face in front of ears

Question 25

VII. Facial

Answer 25

- mixed - Motor - --- supply to muscles of facial expression - --- autonomic innervation to glands of the head - Sensory - --- taste to anterior 2/3 of tongue - 6 branches

Question 26

6 branches of the Facial Nerve (CN VII)

Answer 26

1. Temporal 2. Zygomatic 3. Buccal 4. Mandibular 5. Cervical 6. Post Auricula

Question 27

Bell's Palsy

Answer 27

- VII. Facial nerve - facial paralysis resulting from damage to the facial nerve - cause is often unknown - --- may be related to trauma or infection - symptoms may begin suddenly and reach their peak within 48 hours - symptoms range in severity from mild weakness to total paralysis - --- weakness in muscles of facial expression (upper and lower) - most people recover in 2 weeks to 6 months

Question 28

VIII. Vestibulocochlear

Answer 28

- sensory - goes from medulla to the cochlea and vestibular apparatus in the internal ear - carried afferent fibers for hearing and balance

Question 29

IX. Glossopharyngeal

Answer 29

- mixed - motor - --- stylopharygeus muscle of pharynx - --- parasympathetic: to parotid gland - salivation - sensory - --- taste from posterior 1/3 of tongue - --- chemo and baroreceptors for cardiovascular regulation

Question 30

X. Vagus

Answer 30

- mixed - motor - --- to remaining pharyngeal muscles and laryngeal muscles - --- parasympathetic: heart, lungs, and digestive tract - sensory - --- afferent from chemo and baroreceptors of afferent arch - --- sensation from pharynx, larynx, trachea, and thoracic and abdominal viscera

Question 31

XI. (Spinal) Accessory

Answer 31

- motor - has spinal and cranial roots - axons leave the cranium to innervate the trapezius and sternocleidomastoid muscles

Question 32

Clinical Correlation: accessory nerve injury

Answer 32

- weakness in the fibers of the trapezius can be caused by compression of the accessory

Question 33

XII. Hypoglossal

Answer 33

- motor | - to muscles of the tongue

Question 34

Clinical correlation: hypoglossal injury

Answer 34

- hypoglossal nerve function is tested by asking the patient to protrude her tongue - if the hypoglossal nerve is injured, the tongue deviates toward the side of the lesion - --- toward the weak side