Cranial Nerves Continued Flashcards
GSE
General Somatic Efferent: motor fibers to skeletal musculature (VOLUNTARY)
GSA
General Somatic Efferent: motor fibers to skeletal musculature (VOLUNTARY)
GVE
General Visceral Efferent: motor fibers to smooth muscle, glands, and viscera (INVOLUNTARY)
GVA
General Visceral Afferent: fibers that carry visceral sensation
BE/SVE
Branchial Efferent/Special Visceral Efferent: motor fibers to skeletal, voluntary muscles that developed from branchial (pharyngeal) arches
SVA
Special Visceral Afferent: taste & smell
SSA
Special Somatic Afferent: vision, hearing & balance
Parasympathetic GVE fibers reside ONLY in what nerves? And what are their associated ganglion?
CN III: Oculomotor
CN VII: Facial
CN IX: Glossopharyngeal
CN X: Vagus
CN III = Ciliary Ganglion
CN VII = Pterygopalatine & Submandibular Ganglion
CN IX = Otic Ganglion
CN X = Various ganglia near visceral organs
Branchial Motor (BE/SVE) fibers reside ONLY in nerves associated with what? What are they?
(see chart on slide 7)
pharyngeal (branchial) arches
I –> CN V3 (mastication)
II –> CN VII (facial expression)
III –> CN IX (?)
IV –> CN X (pharyngeal constrictors- swallowing to move bolus to esophagus)
VI –> CN X (larynx muscles - voice box)
CN V - trigeminal nerve pathway:
Pathway:
Begins at pons and travels superiorly/anteriorly towards face
Splits into three terminal divisions at “trigeminal ganglion” in middle cranial fossa
V1 = Ophthalmic (upper face)
V2 = Maxillary (mid face)
V3 = Mandibular (lower face)
Each terminal branch exits the skull via a different foramen and innervates a different region of the face
BE/SVE Modality
Arch 1
Muscles of mastication
What are the 3 Trigeminal Sensory Nuclei and what are their actions?
1.) Spinal nucleus of the trigeminal nerve: Pain the Tem & light touch.
2.) Chief or principal nucleus or main sensory nucleus: discriminative sensation and light touch as well as conscious proprioception.
3.) Mesencephalic nucleus: proprioception
CN V1= Ophthalmic pathway
Pathway: Ophthalmic division 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 & ethmoidal sinuses
dura mater of anterior cranial fossa
How do you test CN V1?
Test sensation of forehead
CN V1 – corneal reflex
V2 = maxillary pathway:
Pathway: 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
What is the function of CN V2?
Test sensation of lateral nose, cheek and upper jaw
CN V3 = mandibular pathway (lower face):
Pathway: 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
CN V extensively innervates __________ mater. Causing what?
dura mater
Headache due to referring pain from some pathological conditions in the head region!
V3 = mandibular pathway (arch 1 and mastication)
Foramina: Ovale
Function: BE/SVE Modality
Arch 1
Voluntary motor control to muscles of mastication
Temporalis
Masseter
Medial pterygoid
Lateral pterygoid
Collectively these muscles open/close the mandible for chewing action
What muscle contracts primarily to dampen the noise produced by chewing? Of CN V?
tensor tympani muscle
The tensor tympani muscle, innervated by the mandibular branch of CN V, connects the auditory tube to the malleus handle. It increases the tension in the tympanic membrane, thus protecting it from excessive vibration in response to loud sounds.
What is trigeminal neuralgia?
Neuralgia: sensation of pain elicited without presence of noxious stimuli
Often develops without any cause
Intermittent attacks of severe, sharp, stabbing pain “electric shock”
Most often affects CN V2 and V3
Affects GSA code only*
No motor deficits
Unilateral distribution
Seen m/c in females (50+)
Aggravated by:
Exposure to cold
Chewing
Brushing teeth
Talking
Touching face
Treatment usually involves medications which block incoming pain signals into CNS
VII = Facial nerve
Fiber types? Foramina?
FIBER TYPES OF FACIAL NERVE:
(BE/SVE, SVA, GVE, GSA)
1.) BE/SVE axons to muscles of facial 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 AND Stylomastoid
What is the pathway of CN VII Facial Nerve?
Pathway:
Facial nerve 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
Within temporal bone, nerve gives off several intracranial branches
Remaining nerve will exit the cranial base via the stylomastoid foramen.
Foramina: Internal Acoustic Meatus AND Stylomastoid Foramen
Once nerve exits skull – it gives rise to 6 extracranial branches
What are the intracranial branches of the facial nerve VII?
Intracranial branches:
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)
The primary gustatory region of the cortex is found where?
the insula
What are the extracranial branches of CN VII?
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
What attaches to the stapes and helps to dampen sounds (i.e. protects from intense/loud sounds and dampens endogenous sounds such as chewing, talking, and swallowing)? CN VII
the stapedius (SVE component)
What condition results from trauma to the facial nerve, such as a viral meningitisinfection. With symptoms including:
1.) Weakness, twitching, or paralysis of facial muscles, including drooping of the eyelid and corner of the mouth. Damage to what portion of the facial nerve would these symptoms result from?
2.) Dry eye or mouth. Damage to what portion of the facial nerve would these symptoms result from?
3.) Impairment of taste. Damage to what portion of the facial nerve would these symptoms result from?
Bell’s Palsy
SVE portion
GVE component
SVA component
Corneal reflex does what? Motor arc? Sensory arc? Desired response? Test? Clinical significance?
Corneal Reflex = protects eyes from foreign bodies
Sensory arc: CN V1 (touch to surface of cornea)
Motor arc: CN VII (orbicularis oculi)
Desired response = BILATERAL regardless of input side!
TEST: Cotton gauze touched to cornea of R eye should result in blink/closure of BOTH eyes
Clinical significance?
Cotton gauze touched to L eye, only R eye blinks means sensory signal worked, but L motor did not work
Cotton gauze touched to L eye, and no eyes blink means sensory input did not work
Review slide 39 chart
What is the pathway for CN VIII = vestibulocochlear Nerve
Two separate nerves that travel together
Pathway:
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)
What is the pathway for CN IX = Glossopharyngeal Nerve?
Pathway:
Nerve emerges from the brainstem in the lateral medulla and exits the posterior cranial fossa through the jugular foramen.
Majority of nerve remains extracranial to innervate structures of face and throat
Foramina: Jugular foramen
Function:
Glossopharyngeal has five (5) modalities
BE/SVE – voluntary motor
SVA – special visceral afferent
GVE – general visceral efferent
GVA – general visceral afferent
GSA – general somatic afferent
What are the fiber types of the glossopharyngeal nerve (CN IX)?
BE/SVE axons innervate stylopharyngeus (swallowing muscle)
SVA axons carry taste perception from the posterior 1/3 of the tongue
GVE axons innervate the parotid gland via otic ganglion (secretomotor function)
GVA axons from the carotid body (visceral sensation from carotid body for chemoreception – maintaining BP)
GSA axons - sensory from skin posterior to the ear, posterior 1/3 of tongue, and the afferent part of the gag reflex
Pathway for CN X - Vagus Nerve?
Pathway:
Nerve emerges from the brainstem in the lateral medulla and exits the posterior cranial fossa through the jugular foramen.
Foramina: Jugular foramen
Function:
Vagus nerve has five (5) modalities
BE/SVE – voluntary motor
SVA – special visceral afferent
GVE – general visceral efferent
GVA – general visceral afferent
GSA – general somatic afferent
What are the fiber types of the vagus nerve (CN X)?
(1) BE/SVE axons innervate the majority of the muscles of the pharynx, larynx and soft palate (moving food towards esophagus during swallowing)
(2) GSA axons from skin posterior to ear, dura in posterior cranial fossa, mucous membranes of pharynx & larynx
(3) GVA axons from thoracic & abdominal viscera & aortic body
Chemoreceptors – blood content
Baroreceptors – blood pressure
(4) SVA axons (taste) from the root of tongue and epiglottis region
(5) GVE axons (parasympathetic) to thoracic and abdominal viscera up to left colic flexure. Synapse is in or around target organ.
Vagus Nerve injury
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
What reflex is initiated in response to stroking the back of the throat and is mediated by the vagus nerve?
The gag reflex
Gag Reflex = helps prevent choking
Sensory arc: CN IX (touch to base of throat)
Motor arc: CN X (motor response of pharynx)
Desired response = 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 problem = 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
What is the pathway for spinal accessory nerve CN XI?
Pathway: 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 (GSE)
What is the pathway of the hypoglossal nerve? (CN XII)
Pathway: 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)
What is the exception to the usual bilateral innervation that the cortex sends?
genioglossus muscle (contralateral)
Common injury of the hypoglossal nerve CN XII? How do you test for it?
Pathway: 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)
Testing CN XII= “Stick out your tongue”
