Neuroanatomy lecture 6: Cranial nerves continued

Question 1

GSE (general somatic efferent):

Answer 1

motor fibers to skeletal muscle (voluntary)

Question 2

GSA (general somatic afferent):

Answer 2

fibers that carry general sensation (touch, pressure, pain, proprioception, temp, tickle and vibration)

Question 3

GVE (General visceral efferent):

Answer 3

motor fibers to smooth muscle, glands, and viscera (involuntary)

Question 4

GVA (general visceral afferent):

Answer 4

fibers that carry visceral sensation

Question 5

BE/SVE (brachial efferent/special visceral efferent):

Answer 5

motor fibers to skeletal, voluntary muscles that developed from brachial (pharyngeal) arches

Question 6

SVA (special visceral afferent):

Answer 6

taste & smell

Question 7

SSA (special somatic afferent):

Answer 7

vision, hearing, & balance

Question 8

parasympathetic GVE fibers reside only in:

Answer 8

CN III: oculomotor
-ciliary ganglion

CN VII: facial
-pterygopalatine & submandibular ganglion

CN IX: glossopharyngeal
-otic ganglion

CN X: vagus
-various ganglia near visceral organs

Question 9

Branchial motor (BE/SVE) fibers reside only in nerves associated with ___________ ___________ arches.

Answer 9

pharyngeal (branchial)

Question 10

CN V: trigeminal nerve:

Answer 10

major sensory pathway for the face

pathway:
-begins at pons and travels superiorly/anteriorly towards face
-splits into three terminal divisions as trigeminal ganglion in middle cranial fossa
V1 = Opthalmic
V2 = maxillary
V3 = Mandibular

Each terminal branch exits the skull via a different foramen and innervates a different region of the face.

Question 11

Trigeminal ganglion:

Question 12

V1 =>

Answer 12

Opthalmic

GSA modality

-upper face

Question 13

V2 =>

Answer 13

Maxillary

GSA Modality

-Mid face

Question 14

V3 =>

Answer 14

Mandibular

GSA modality
-Lower face

BE/SVE modality
-Arch 1
-Muscles of mastication

Question 15

Spinal nucleus of the trigeminal nerve:

Answer 15

pain, temp & light touch

Question 16

Chief or principle nucleus or main sensory nucleus:

Answer 16

discriminative sensation and light touch as well as conscious proprioception

Question 17

Mesencephalic nucleus:

Answer 17

proprioception

Question 18

V1 opthalmic pathway:

Answer 18

passes through the cavernous sinus, exits via superior orbital fissure & has many additional branches from there.

Foramina: superior orbital fissure

Function: GSA modality
general sensory to:
-forehead
-anterior scalp
-upper eyelid
-tip of the nose
-anterior nasal cavity
-frontal and ethmoidal sinuses
-dura mater of anterior cranial fossa

Testing CN V1:
1) testing sensation of forehead
2) CN V1: corneal reflex

Question 19

V2 maxillary pathway:

Answer 19

passes through the cavernous sinus, exits skull via foramen rotundum to innervate face

Foramina: Rotundum

Function: GSA Modality
general sensory to:
-the sides of the nose
-lower eyelids
-upper lip
-posterior nasal cavity
-teeth of the upper jaw
-maxillary sinus
-nasopharynx
-palate
-dura of the middle cranial fossa

Testing V2:
1) testing sensation of the lateral nose, cheek and upper jaw

Question 20

V3 mandibular pathway:

Answer 20

not associated with cavernous sinus, exits skull via foramen ovale to innervate lower face

Foramina: Ovale

Function: GSA modality
general sensory to:
-lower lip
-chin
-lower face & cheek
-anterior external ear
-teeth of mandible
-mucous membranes of cheek
-anterior 2/3 of tongue
-dura in the middle cranial fossa

Question 21

CN V extensively innervates the _________________

Answer 21

dura mater

-headache due to referring pain from some pathological conditions in the head region

Question 22

V3 mandibular BE/SVE modality:

Answer 22

foramina: Ovale

Function:
-Arch 1
-Voluntary motor control to muscles of mastication:
-temporalis
-masseter
-medial pterygoid
-lateral pterygoid

Question 23

Tensor tympani muscle:

Answer 23

innervated: mandibular branch of CN V

Connects to: auditory tube in malleus handle

Increases tension in the tympanic membrane and protects it from excessive vibration in response to loud sounds.

The muscle is contracted primarily to dampen the noise produced by chewing.

Question 24

Trigeminal neuralgia:

Answer 24

sensation of pain elicited w/o presence of noxious stimuli

-often develops w/o any cause
-Intermittent attacks of severe, sharp, stabbing pain “electric shock”
-Most often affects CN V2 & V3
(affects the GSA code only*)
(no motor deficits)

-unilateral distribution
-Seen m/c distribution

Aggravated by:
-exposure to cold
-chewing
-brushing teeth
-talking
-touching face

Question 25

Fiber types of the facial nerve:

Answer 25

1) BE/SVE: axons to muscle of fascial expression (arch II) 2) SVA: axons (taste) from the anterior 2/3rds of the tongue 3) GVE: axons to the submandibular, sublingual and lacrimal glands 4) GSA: axons for the "patch" of skin behind the ear Foramina: internal acoustic meatus & stylomastoid

Question 26

CN VII: Facial Nerve pathway:

Answer 26

Originates from the pons and first exits skull through the internal acoustic (auditory) meatus winding through the petrous portion of the temporal bone (facial canal) Infection in the middle/inner ear can impact CN VII Which temporal bone, nerve gives off several intracranial branches remaining nerve will exit the cranial base via the stylomastoid foramen Foramina: internal acoustic meatus & stylomastoid foramen Once nerve exits skull: it gives rise to 6 extracranial branches

Question 27

Intracranial branches of CN VII:

Answer 27

chorda tympani carries GVE and SVA: -branches off main nerve in the facial canal (inside skull) SVA=special visceral afferent -carrying taste perception from the anterior 2/3rds of the tongue GVE= general visceral efferent -secretomotor of the submandibular and sublingual glands via submandibular ganglion = saliva production Greater petrosal nerve carries GVE -exits the petrous portion of the temporal bone where parasympathetic axons synapse in the pterygopalatine ganglion GVE = general visceral efferent -secretomotor to lacrimal gland of eye (tear production)

Question 28

The primary gustatory region of the cortex is found in:

Answer 28

The insula 1) 1st order neuron 2) 2nd order neuron 3) 3rd order neuron

Question 29

GVE component of CN VII:

Answer 29

Question 30

Extracranial branches of CN VII:

Answer 30

BE/SVE modality= voluntary motor control to muscles of facial expression 5 branches: -temporal -zygomatic -buccal -mandibular -cervical GSA modality = GAS to skin behind the ear -posterior auricular branch

Question 31

The stapedius attaches to the _________and helps dampen the sounds:

Answer 31

stapes -protects from the intense/loud sounds and dampens endogenous sounds such as chewing, talking, and swallowing

Question 32

Bell's palsy:

Answer 32

results from trauma to the facial nerve, such a viral meningitis infection. A wide variety of symptoms can manifest, including: weakness, twitching, or paralysis of facial muscles, including droopy eyelid and corner of the mouth. These symptoms would result from damage of the SVE portion of the facial nerve. Dry eye or mouth: result from damage from the GVE component of the nerve Impairment of taste: damage to the SVA component of the nerve

Question 33

Corneal reflex:

Answer 33

blinking an eye protects eyes from foreign bodies -sensory arc: CN V1 (touch to surface of cornea) -motor arc: CN VII (orbicularis oculi) Bilateral regardless of input side. Test: cotton gauze touched to the cornea of R eye should result in blink/closure of both eyes Clinical significance: -cotton gauze to L eye and only R blinks: sensory signal worked but L motor didn't work -Cotton gauze to L eye, and no eyes blink: sensory input didn't work

Question 34

CN VIII: vestibulocochlear nerve pathway:

Answer 34

two separate nerves that travel together: -begins at base of pons and exits cranium via internal acoustic meatus. Terminates as separate nerves in inner ear. Foramina: Internal acoustic meatus Function: special somatic afferent (SSA) for two senses: -Hearing (cochlear) -Balance & equilibrium (vestibular)

Question 35

CN IX: glossopharangeal nerve pathway:

Answer 35

-nerve emerges from the brainstem in the lateral medulla and exits the posterior cranial fossa through the juguular foramina -Majority if nerve remains extracranial to innervate structures of face and throat Foramina: jugular foramen Function: (5 modalities) 1) BE/SVE: voluntary motor -axons innervate stylopharyngeus (swallowing muscle) 2) SVA: special visceral afferent -carry taste perception from the posterior 1/3 of the tongue 3) GVE: general visceral efferent -innervate the parotid gland via otic ganglion (secretomotor function) 4) GVA: general visceral afferent -from carotid body (visceral sensation from carotid body for chemoreception-maintaining BP) 5) GSA: general somatic afferent -sensory from skin posterior to the ear, posterior 1/3 of tongue, and the afferent part of the gag reflex

Question 36

CN X: vagus nerve pathway:

Answer 36

nerve emerges from the brainstem in the lateral medulla and exits the posterior cranial fossa through the jugular foramen. Foramina: Jugular foramen Function: (5 modalities) 1) BE/SVE (voluntary motor): -innervate the majority of the muscles of the pharynx, larynx, and soft palate (moving food towards esophagus during swallowing) 2) SVA (special visceral afferent): -axons from skin posterior to ear, dura in posterior cranial fossa, mucous membranes of pharynx & larynx 3) GVE (general visceral efferent): -axons from thoracic and abdominal viscera & aortic body chemoreceptors: blood content baroreceptors: blood pressure 4) GVA (general visceral afferent): -axons (taste) from the root of tongue and epiglottis region 5) GSA (general somatic afferent): -thoracic and abdominal viscera up to left colic flexure. Synapse is in or around target organ.

Question 37

Vagus nerve injury:

Answer 37

Recurrent laryngeal nerve branch: BE/SVE: branchial efferent/special visceral efferent: -nerve supplies muscles of the larynx/voice box -travels posterior to thyroid Common causes of injury: -Tumor or after surgical intervention of the thyroid -Bronchial carcinoma -Aortic arch aneurysm Patient presentation includes: -Hoarse voice -Vocal changes (dysphonia) -Difficulty producing speech

Question 38

Vagus nerve GVE parasympathetic outflow:

Answer 38

Question 39

The gag reflex is initiated by stroking the back of the throat and is mediated by:

Answer 39

the vagus nerve

Question 40

Gag reflex:

Answer 40

help prevent choking sensory arc: CN IX (touch base of throat) Sensory arc: CN X (motor response to pharynx) Bilateral regardless of input side Test: touch one side of the oropharynx should result in contraction of soft palate muscles of both sides (sometimes this can be elicited by just asking patient to say "ahhhh") Clinical significance: -CN X motor problems: uvula will deviate to the intact side (away from side of injury) -CN IX sensory problem: NO response (soft palate muscles do not contract at all) -Protective response that prevents oral contents from entering the throat except as part of normal swallowing

Question 41

CN XI: spinal accessory pathway:

Answer 41

nerve begins at medulla and exits cranium via jugular foramen Foramina: jugular foramen Function: voluntary motor to sternocleidomastoid and trapezius muscles SCM -contralateral rotation of head Traps- shoulder "raises" (general somatic efferent)

Question 42

CN XII: hypoglossal nerve pathway:

Answer 42

nerve begins at medulla and exits cranium via hypoglossal canal Foramina: hypoglossal canal Function: voluntary motor to muscles of the tongue (general somatic efferent (GSE))

Question 43

The cortex normally sends bilateral innervation to cranial nerve motor nuclei. The one exception is innervation of the ___________________ which is contralateral.

Answer 43

genioglossus muscle

Question 44

CN XII: hypoglossal nerve injury:

Answer 44

Common causes of injury: -fairly rare -posterior neck dissection -fracture of atlanto-occipital joint Patient presentation includes: -Tongue deviated to same side as injury due to atrophy of muscles -"lick your wounds" presentation -Dysphagia (difficulty swallowing) -Slurred speech -Fasciculation on the tongue "bag of worms" appearance Testing CN XII: "stick out your tongue"