Head: Cranial Nerves I-V

Question 1

Cranial nerves

Answer 1

• 12 in number (Roman numerals)
• Originate from brainstem
• Supply function primarily to the head/neck

Question 2

Cranial nerve nucleis originate

Answer 2

• From brainstem

Question 3

All cranial nerves originate from brainstem EXCEPT

Answer 3

• CN I, II, XI

Question 4

CN supplying function primarily to the head/neck

Answer 4

• CN X, vagus

- Leaves the head/neck region

Question 5

Cranial nerves exit the cranial cavity through

Answer 5

• Skull foramina

Question 6

CN sensory ganglia function

Answer 6

• Visceral/reflexive
• Somatic sensation
• Special sensory

Question 7

CN motor function

Answer 7

• Somatic
• Visceral (parasympathetic)
• Pre and postsynaptic
• Parasympathetic ganglia

Question 8

Sensory only CNs

Answer 8

• I, II, and VIII

Question 9

CN involved with motor

Answer 9

• III, IV, V, VI, VII, IX, X, XI, XII

Question 10

CN involved with sensory

Answer 10

• I, II, V, VII, VIII, IX, X

Question 11

CN involved with both sensory and motor

Answer 11

• V, VII, IX, X

Question 12

CN with parasympathetic function

Answer 12

• III, VII, IX, X

Question 13

Cranial nerve I

Answer 13

• Olfactory nerve

Question 14

Olfactory nerve (CN I)

Answer 14

• Collection of nerves
• Pass through olfactory foramina in the cribriform plate
• Enter cerebellum directly

Question 15

Olfactory nerve (CN I) function

Answer 15

• Special sensory

- Smell (taste)

Question 16

Clinical importance of olfactory nerve (CN I)

Answer 16

• Fracture of cribriform plate
• Trauma
• Anosmia: loss of smell
• CSF leakage (CSF rhinorrhea)

Question 17

Cranial nerve II

Answer 17

• Optic nerve

Question 18

Optic nerve (CN II)

Answer 18

• Extensions of the forebrain
• Surrounded by meninges and CSF
• Passes through optic canal
• Forms optic chiasm
• Central retinal artery travels within (branch of ophthalmic)

Question 19

Optic nerve (CN II) function

Answer 19

• Vision

Question 20

Clinical importance of optic nerve (CN II)

Answer 20

• Can be affected by demyelinating disorders

- Injury can cause visual field defects (neuroanatomy topic)

Question 21

Cranial nerve III

Answer 21

• Occulomotor nerve

Question 22

Occulomotor nerve (CN III)

Answer 22

• Arises from midbrain
• Passes through cavernous sinus
• Enters orbit through superior orbital fissure
• Contains parasympathetic to intrinsic eye muscles

Question 23

Occulomotor nerve (CN III) innervates

Answer 23

• 4/6 extraocular muscles

- Levator palpebrae

Question 24

Occulomotor nerve (CN III) divides into

Answer 24

• Superior division

- Inferior division

Question 25

Superior division of occulomotor nerve (CN III)

Answer 25

- Superior rectus muscle | - Levator palpebrae superioris muscle

Question 26

Inferior division of occulomotor nerve (CN III)

Answer 26

- Inferior and medial recti muscles - Inferior oblique - Presynaptic parasympathetics --> ciliary ganglion

Question 27

Injury to occulomotor nerve (CN III)

Answer 27

- Loss of certain eye movements - Down and out pupil - Ptosis - Dilated pupil - Loss of pupillary light response (parasympathetics)

Question 28

Loss of pupillary light response (parasympathetics) from occulomotor nerve (CN III) injury results in

Answer 28

- Constriction of pupil in response to light

Question 29

Trochlear nerve (CN IV)

Answer 29

- Exits midbrain dorsally - Longest intracranial course - Passes through cavernous sinus lateral wall - Exits cranium through superior orbital fissure

Question 30

Trochlear nerve (CN IV) function

Answer 30

- Innervates superior oblique muscle | - Depresses, abducts, intorts eye

Question 31

Cranial nerve IV

Answer 31

- Trochlear nerve

Question 32

Clinical importance of Trochlear nerve (CN IV)

Answer 32

- Damaged in head injuries - Loss of depression when affected eye is adducted - Head tilt

Question 33

Cranial nerve V

Answer 33

- Trigeminal nerve

Question 34

Trigeminal nerve (CN V)

Answer 34

- Multiple brainstem nuclei - Exits pons - Sensory root - Motor roots

Question 35

Sensory root of Trigeminal nerve (CN V)

Answer 35

- Trigeminal ganglion

Question 36

3 divisions of Trigeminal nerve (CN V)

Answer 36

- Ophthalmic (V1) - Maxillary (V2) - Mandibular (V3)

Question 37

Ophthalmic division of Trigeminal nerve (CN V) passes through

Answer 37

- Superior orbital fissure

Question 38

Maxillary division of Trigeminal nerve (CN V) passes through

Answer 38

- Foramen rotundum

Question 39

Mandibular division of Trigeminal nerve (CN V) passes through

Answer 39

- Foramen ovale

Question 40

Ophthalmic nerve (V1) is

Answer 40

- Purely sensory

Question 41

Ophthalmic nerve (V1) innervates

Answer 41

- Portion of the dura mater - Forehead, anterior scalp - Dorsum of nose - Anterior/superior nasal cavity - Sinuses except for maxillary - Cornea

Question 42

Ophthalmic nerve (V1) innervation to cornea

Answer 42

- Afferent limb of corneal reflex | - Efferent is facial nerve

Question 43

Maxillary nerve (V2) is

Answer 43

- Purely sensory

Question 44

Maxillary nerve (V2) innervates

Answer 44

- Dura mater - Posterior/inferior nasal cavity - Maxillary sinus - Palate - Superior oral vestibule - Maxillary teeth - External lateral nose, lower eye lid - Skin over upper jaw/lip

Question 45

Mandibular nerve (V3) is

Answer 45

- Both sensory and motor

Question 46

Sensory innervation of Mandibular nerve (V3)

Answer 46

- Sensation anterior 2/3 tongue - Floor of oral cavity/vestibule - Mandibular teeth - Skin of lower lip, chin, cheek, temporal region, anterior ear - External acoustic meatus and tympanic membrane

Question 47

Motor innervation of Mandibular nerve (V3)

Answer 47

- Muscles of mastication - Tensor veli palatine - Tensor tympani - Mylohyoid - Anterior belly of digastric

Question 48

Lesion to Trigeminal nerve (symptoms depend on location of injury) may cause

Answer 48

- Loss of ipsilateral corneal reflex and jaw jerk reflex - Loss of ipsilateral face sensation - Muscle of mastication weakness - Jaw deviates to involved side when opened