Cranial Nerves - function & testing, nuclei location

Question 1

Olfactory

Answer 1

CN I - sensory

FUNCTION: smell

Question 2

Optic

Answer 2

CN II - sensory

FUNCTION: vision, sensory portion of pupillary reflex

Question 3

Oculomotor

Answer 3

CN III - motor

FUNCTION: move eyes up, down, medially, raise eyelid, constrict pupil & adjust lens shape (ciliary muscles)

(aka pupillary reflex - motor portion, convergence & accomodation)

KNOW FOR PNS - innervates ciliary muscles & pupil

Question 4

Trochlear

Answer 4

CN IV - motor

FUNCTION: move eye medially & down

Question 5

Trigeminal

Answer 5

CN V - both

FUNCTION: facial sensation, chewing (masseter muscle & jaw movements), sensation from TMJ

Question 6

Abducens

Answer 6

CN VI - motor

FUNCTION: abduct eye

Question 7

Facial

Answer 7

CN VII - both

FUNCTION: muscles of facial expression, closes eyes, tears (lacrimal gland), salivation (salivary gland) & taste

FOR PNS - innervates lacrimal & salivary gland

Question 8

Vestibulocochlear

Answer 8

CN VII - sensory

FUNCTION; sensation of head position relative to gravity (vestibular system), & hearing

Question 9

Glossopharyngeal

Answer 9

CN IX - both

FUNCTION: swallowing (muscles of pharynx), salivation, & taste

FOR PNS - know innervates salivary gland
–> sensory part (afferent limb) of gag reflex

Question 10

Vagus

Answer 10

CN X - both

FUNCTION: autonomic regulation of viscera, swallowing, gag reflex, speech & taste
–> motor portion (efferent limb) of gag reflex

PNS innervation of viscera including - heart, trachea, stomach, liver, pancreas, kidney small intestine

(basically everything except ext genitalia, colon & bladder - S3/4 complex)

Question 11

Accessory

Answer 11

CN XI - motor

FUNCTION: elevate shoulders & turn head (trap & STM)

Question 12

Hypoglossal

Answer 12

CN XII - motor

FUNCTION: move tongue

Question 13

Taste - which CN’s are involved?

Answer 13

Facial (VII), Hypoglossal (IX), & vagus (X)

Question 14

Preganglionic cell bodies of CN involved in PNS

Answer 14

Oculomotor (III), facial (VII), Hypoglossal (IX) & vagus (X)

Question 15

Superior medulla - CN Nuclei

Answer 15

CN X (solitary, nucleus ambiguus & dorsal motor)

CN XII (hypoglossal nucleus)

Question 16

Inferior midbrain - CN Nuclei

Answer 16

CN IV (nucleus of trochlear nerve - ONLY nerve to exit brainstem POSTERIORLY)

Question 17

Superior midbrain - CN Nuclei

Answer 17

CN III (oculomotor nucleus)

Question 18

Inferior Pons - CN Nuclei

Answer 18

CN VI (abducens nuclei)

CN VII (facial nuclei - wraps around CN VI nuclei)

CN VIII (vestibular & chochlear nuclei)

Question 19

Superior Pons - CN Nuclei

Answer 19

CN V (trigeminal sensory & motor nuclei)

Question 20

Inferior medulla - CN Nuclei

Answer 20

none of importance!

Question 21

Corticobulbar tract

• what does it do
• where does it start
• which CN’s

Answer 21

controls the MOTOR portion of the CN’s

• starts in motor areas of the cortex & projects to CN nuclei in the brainstem which
• facilitates LMN’s innervating muscles of head and neck

All project bilaterally EXCEPT: CN V, VII and XII (nerves that control muscles of the lower face)

–> they are controlled by CONTRALATERAL corticobulbar tracts

Question 22

Lesion of LMN of CN vs. Lesion of Corticobulbar tract

Answer 22

Lesion of LMN: loss of motor input to upper AND lower portion of the face on the SAME side of the lesion
i.e. cant smile or close eyes

Lesion of corticobulbar tract: loss of LOWER portion of CONTRALATERAL face
- i.e. cant smile on opposite side of the face

Question 23

Pupillary Reflex - sensory & motor portion

Answer 23

the sensory portion (afferent limb) of the pupillary reflex is detected by CN II (optic)

the motor portion (efferent limb), actual constriction or dilation of the pupil is performed by CN III (oculomotor)

Question 24

Eye accomodation

• which CN
• what happens

Answer 24

CN III (oculomotor)

Near object - pupil constricts
Far object - pupil dilates