2. Introduction to Cranial Nerves
Terms
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- List 3 functions of cranial nerves:
-
1. To provide motor/sense innervation to head/neck
2. To innervate special sense organs
3. To carry ANS fibers - What are the 3 sensory modalities of cranial nerves?
-
1. Special sense
2. Somatic sense
3. Visceral sense - What information is obtained by special sensory nerves?
-
-Smell (CN I)
-Vision (CN II)
-Taste (CNs VII, IX, X)
-Hearing/Balance (CN VIII) - What info is obtained by somatic sensory nerves?
- Proprioception, pain, temp, vibration, touch, from the skin and body wall.
- What info is obtained by visceral sensation?
- Info re: glands and organs in thoracic/abdominal/pelvic cavities
- What is visceral motor innervation responsible for?
- Innervation of cardiac muscle, smooth muscle, and glands.
- What is branchial motor innervation responsible for?
- Innervation of muscles derived from branchial arches
- What 4 types of muscles are branchially derived?
-
-Mastication
-Face expression
-Pharynx
-Larynx - What is somatic motor innervation responsible for?
- Innervation of skeletal muscles from myotomes
- What muscles in the head are considered somatic?
-
Extraocular
Tongue - What nerves are purely special sensory?
-
I - olfactory
II - optic
VIII - acoustic
CAPOLO in reverse - What nerves are purely somatic motor?
-
IV - Trochlear
VI - Abducens
XII - Hypoglossal
HAT - What cranial nerves are special sensory?
- One, Two, and 7-10
- What cranial nerves are somatic sensory?
-
5, 7, 9, 10
the store and one more - What cranial nerves are visceral sensory?
- 9 and 10
- What cranial nerves are visceral motor?
- 3, 7, 9, 10
- What cranial nerves are branchial motor?
-
5, 7, 9, 10, 11
the store and two more - What cranial nerves are somatic motor?
- 3, 4, 6, 12
- Purely sensory cranial nerves:
- 1, 2, 8
-
CN 1 - Olfactory:
-Function
-Neuron cell body locations
-Skull passage
-Injury
-Possible cause of injury -
Function = smell
NCB = olfactory epithelium
Skull hole = cribiform plate
Injury = anosmia
Cause = fracture of crib plate -
CN II - optic
-Function
-Neuron cell body locations
-Skull passage
-Injury
-Possible cause of injury -
-Function = vision
NCB = back of retina
-Skull passage = optic canal
-Injury = anopsias
-Cause = eyeball trauma -
CN VIII - Vestibulocochlear
-Function
-Neuron cell body locations
-Skull passage
-Injury
-Possible cause of injury -
Function = hearing and balance
NCB = Cochlea (spiral ganglion) and Semicircular canals (vestibular ganglion)
Skull hole = internal acoustic meatus
Injury: hearing impaired or loss, tinnitus, vertigo
Cause: tumor - Purely MOTOR nerves:
- 3, 4, 6, 11, 12
-
CN III - Oculomotor
-Function
-Neuron cell body locations
-Skull passage -
Function = eye movement
NCB: upper midbrain oculomotor nucleus
Hole: superior orbital fissure - What is the route of the oculomotor nerve (4 points)
-
1. Emerges near median plane at midbrain/pons junction
2. Passes between posterior cerebral & superior cerebellar arteries
3. Passes through cavernous sinus & Superior orbital fissure
4. Passes within common tendinous ring of rectus muscles - What 5 muscles does CN III innervate?
-
1. Levator palpebrae
2. Superior rectus
3. Inferior rectus
4. Medial rectus
5. Inferior oblique - What are 3 types of CN 3 injuries?
-
1. Ptosis
2. Lateral stabismus
3. Diplopia - what is ptosis?
- When the eyelid droops due to paralysis of levator palpebrae
- What is lateral strabismus?
- When the eye turns down and laterally due to unopposed action of superior oblique and lateral rectus
- What is diplopia?
- double vision due to lateral strabismus
- What are 2 possible causes of oculomotor nerve injuries?
-
1. Cavernous sinus injury
2. Aneurysms of posterior cerebral or superior cerebellar arteries. -
CN IV - Trochlear
-Function
-Neuron cell body locations
-Skull passage
-Structure innervated -
Function: eye movement
NCB: lower midbrain trochlear nucleus
Skull hole: superior orbital fissure
Innervates Superior oblique m - Descrie the route of the trochlear (CN IV) nerve (3 points):
-
1. Emerges from dorsal midbrain
2. Passes thru cavernous sinus and superior orbital fissure
3. Passes outside common tendinous ring from which rectus muscles originate - What is special about the trochlear nerve route?
- It is the only cranial nerve to emerge from the dorsal aspect of the brain.
- How is the eye impaired when CN IV is injured?
- Unable to look down when eye is adducted -> results in diplopia
- What is a possible cause of CN IV injury?
- Cavernous sinus injury
-
CN VI - Abducent
-Function
-Neuron cell body locations
-Skull passage
-Innervated structure -
Function = eye movement
NCB = pons abducent bodies
Skull hole = sup. orbital fiss.
Innervates lateral rectus m. - Describe the route of CN VI (3 points):
-
1. Emerges near median plane at junction of pons/medulla
2. Passes thru cavernous sinus and superior orbital fissure
3. Passes within common tendinous ring from which rectus muscles originate - 2 types of abducent nerve injuries:
-
Medial strabismus
Diplopia - What is medial strabismus?
- Eye turns medially due to unopposed action of medial rectus m.
- What is diplopia again?
- double vision due to medial strabismus
- What are 2 possible causes of abducent nerve injuries?
-
1. Cavernous sinus injury
2. Fracture of skull base -
CN XI - Spinal accessory
-Function
-Neuron cell body locations
-Skull passage
-Injury
-Possible cause of injury -
Function: head/neck movement
NCB: spinal cord - anterior horn of cervical region - How on earth does the spinal accessory nerve enter the skull?
- Through foramen magnum; then it exits through the jugular foramen; how weird...
- hello
- hello
- what does cN XI innervate?
-
-Trapezius
-Sternocleidomastoid - what are 2 types of injuries to the spinal accessory nerve?
-
1. Weak turning head to opposite side
2. Weak shugging shoulders - What could cause injury to CN XI?
- Well a neck laceration; like what if you got into a knife fight, that could do it.. what else?
- So CN XI emerges from the spinal cord; what might be confused with its roots?
- CN X (vagus) also arises from cranial roots, but these are medulla roots; only CN XI arises from spinal cord roots, and it doesn't arise from the medulla at all.
-
CN XII - Hypoglossal:
-Function
-Neuron cell body locations
-Skull passage
-Injury
-Possible cause of injury -
Function = swallow/suck/chew/
stick tongue out.
NCB: medulla - hypoglossal nucleus
Skull hole: hypoglossal canal
Innervates: all tongue muscles iexcept one extrinsic
Injury: unilateral lesion
Cause: neck laceration - What is the route of the hypoglossal nerve? (2 points)
-
1. Emerge from side of medulla (anterior to olives..)
2. pass through hypoglossal canal; curve forward near mandibular angle to "ansa cervicalis" to enter tongue. - What extrinsic tongue muscle does the hypoglossal n NOT innervate? What does innerv. it?
- Palatoglossus - CN X
- What results from a unilateral lesion of the hypoglossal nerve?
- Protruded tongue deviates to one side.
- 3 divisions of CN V:
-
-Ophthalmic
-Maxillary
-Mandibular - What kind fo nerve is each division of CN V?
-
Opthalmic = purely sensory
Maxillary = purely sensory
Mandibular = mixed motor/sensory -
Opthalmic CN V1:
-Function
-NCB location
-Skull hole
-Injury
-Cause of injury -
Function: senssory from skin of forehead, scalp, nasal mucous membranes.
NCB: trigeminal ganglion
Skull hole: Sup orb fissure
Injury: Anesthesia
Cause: inflammation -
Maxillary - CN V2
-Function
-NCB location
-Skull hole
-Injury
-Cause of injury -
Function: Sensory from skin of upper lip, cheek prominence, palate, maxillary sinus.
NCB: Trigeminal ganglion
Skull hole: Forament rotundum
Injury: Anesthesia and Trigeminal neuralgia
Cause: inflammation - What is trigeminal neuralgia, and another name for it?
- Intermittent excruciating pain; aka Tic douloureux
-
Mandibular - CN V3; SENSORY
-Function
-NCB location
-Skull hole
-Injury
-Cause of injury -
Function: sensory from skin of lower jaw, ant 2/3 tongue
NCB: trigeminal ganglion
Skull hole: foramen ovale
Injury: Anesthesia/Trigeminal neuralgia
Cause: inflammation -
Mandibular - CN V3; MOTOR
-Function
-NCB location
-Skull hole
-Injury
-Cause of injury -
Function: branchial motor - swallowing and chewing
NCB: pons - motor nucleus of V
Skull hole: Foramen ovale
Injury: difficulty chewing
Cause: inflammation - 8 muscles innervated by CN V3 - MOTOR:
-
-Temporalis
-Medial/Lateral Pterygoids
-Masseter
-Tensor veli palatini
-Tensor tympani
-Mylohyoid
-Digastric (anterior belly) - What cranial nerves have both sensory and motor functions?
-
V, VII, IX, X
5, 7, 9, 10 (store + 1 more) - The facial nerve has 3 modalities of functions; what are they?
-
-Somatic sensory
-Special sensory
-Branchial motor -
-What is the specific somatic sensory function of CN VII?
-What is its specific special sensory function?
-What is its motor function? -
Somatic sense: skin behind ear, external acoustic meatus, tympanic membrane.
Special sense: taste from anterior 2/3 tongue & palate.
Motor: facial expression -
What is the location of CN VII's
-Sensory NCBs?
-Motor NCBs? -
Sensory = geniculate ganglion
Motor = pons - Through what specific BONE does CN VII enter/exit the skull, and at what parts?
-
TEMPORAL BONE:
Entrance: internal acoustic meatus
Exit: stylomastoid foramen - What will injury to CN VII's somatic sensory component result in?
- Anesthesia
- What will injury to CN VII's SPECIAL sensory component result in?
- Loss of taste sensation in the tongue's anterior 2/3rds.
- What could cause injury to the special sense component of CN VII?
- Injury to the chorda tympani n.
- What are the 5 terminal branches of the facial motor nerve?
-
-Temporal
-Zygomatic
-Buccal
-Mandibular
-Cervical - What 4 structures are innervated by CN VII?
-
-Facial expression muscles
-Stapedius
-Stylohyoid
-Digastric (posterior belly) -
What innervates the digastric
-Anterior belly?
-Posterior belly? -
Ant = V3 - mandibular n.
Post = CN VII - What are the muscles of facial expression?
-
-Orbicularis oculi/oris
-Platysma
-Buccinator
-Frontalis
-Occipitalis - What does an injury to the CN VII result in, and what could cause it?
- Bell's palsy - caused by injury in region of parotid gland.
- What are 4 symptoms of bell's palsy?
-
1. Facial muscle paralysis
2. Inability to close eyes (paralyzed orbicularis oculi)
3. Angle of mouth droops
4. Inability to wrinkle forehead - What type of lesion of CN VII will cause inability to wrinkle forehead, and why?
- Only PERIPHERAL - b/c frontalis is bilaterally innervated.
- Glossopharyngeal CN IX has four functional modalities; what are they?
-
1. Somatic sensory
2. Visceral sensory
3. Special sensory
4. Branchial motor - CN IX - somatic sensory from 7 places:
-
PSTPAMM
-Posterior 1/3rd tongue
-Tonsils
-Soft palate
-Pharynx
-Auditory tube
-Middle ear
-Mastoid air cells -
Where are CN IX's NCBs
-for sensory components?
-for motor components? -
Sensory: Superior ganglion of IX
Motor: nucleus ambiguus in medulla - What path does the glossopharyngeal n. take to get out of the brain?
- Runs along the temporal bone and occipital bone to exit via the jugular foramen.
- What will injury to CN IX do to its somatic sensory abilities?
- Cause dysphagia (difficulty swallowing) and/or dysarthria (speech difficulty)
- What is a possible cause of injury to the glossopharyngeal nerve?
- Neck laceration
- What is the 2 functions of CN IX's visceral sensory ability?
-
1. Detectn of O2 tension in the carotid BODY via chemoreceptors
2. Detectn of blood pressure in carotid SINUS via baroreceptors - How will injury to visceral sensation of glossopharygneal n. manifest?
- As changes in blood pressure
- What is the special sensory function of CN IX?
- Taste from the posterior 1/3rd of tongue.
- What is the branchial motor function of CN IX?
- Phonation - elevation of the pharynx.
- What muscle does CN IX specifically innervate?
- Stylopharyngeus
- What will injury to the motor function of CN IX result in?
- Dysphagia (difficulty swallowing) and/or dysarthria
- CN X - the Vagus nerve - has 4 functional modalities; they are?
-
1. Somatic sensory
2. Visceral sensory
3. Special sensory
4. Branchial motor - From where does CN X receive somatic sensation? (6 places)
- PLEETME: Pharynx, larynx, external ear, external auditory canal, tympanic membrane, and meningies in posterior cranial fossa.
- Where are the somatic sensory NCB's of CN X located?
- In the superior ganglion of CN X
- Where are the special sensory NCB's of CN X located?
- Inferior ganglion of CN X
- Where are the visceral sensory NCB's of CN X located?
- Inferior ganglion of CN X
- Through what bones/hole does the vagus nerve pass thru/exit the skull?
-
-Temporal/occipital bones
-Jugular foramen - What special sensory function does CN X have?
- Taste from the epiglottis
- What are the 3 visceral sensory functions of CN X?
-
1. Sensation in muscles/mucous membranes in pharynx/larynx and thoracid/abdominal viscera
2. Chemoreceptors in AORTIC BODY adjacent to aortic arch
3. Stretch receptors in aortic arch walls - What is the branchial motor functino of CN X?
- Speech
- Where are the motor NCBs of CN X located?
- In the nucleus ambiguus of the medulla
- What branchial muscles are innervated by CN X? (6)
-
-Soft palate skeletal muscles - EXCEPT 2!!
-Pharyngeal constrictor mm
-Levator palati
-Salpingopharyngeus
-Palatopharyngeus
-Palatoglossus - What are the 2 EXCEPTIONS to soft palate muscles innervated by CN X? What are they innervated by?
-
Stylopharyngeus - CN IX
Tensor veli palatini - CN V3 - What are 3 results of injury to the branchial component of the vagus nerve?
-
1. Sagging soft palate
2. Difficulty coughing, swallowing, clearing throat, etc
3. Dysphagia - What does the autonomic nervous system innervate?
-
-Smooth muscle
-Cardiac muscle
-Glands - What are the divisions of ANS?
-
-Sympathetic
-Parasympathetic - What is the format of the ANS?
-
1. Preganglionic NCBs in a brain nucleus OR sp. cd. gray matter.
2. Preganglionic fibers travel WITH CRANIAL NERVES.
3. Preganglionic fibers SYNPSE on postganglnic fiber's cell body in a peripheral ganglion.
4. Postganglnc fibers travel with CRANIAL NERVES
5. Postgnglnc fibers innervate target organs, they respond. - What cranial nerves have autonomic function?
-
3, 7, 9, 10
CN III - oculomotor
CN VII - facial
CN IX - Glossopharyngeal
CN X - Vagus -
CN III:
-Preganglionic NCB location
-Route
-Postganglionic NCB location
-Route
-Target -
Pre NCB: Edinger westphal nuceus in upper midbrain
Pre Route: with CN III
Post NCB: Ciliary ganglion (V1)
Post route: w/ short ciliary n
Target: Sphincter pupillae and Cilary muscles - Loss of CN III autonomic function results in:
-
1. Myodiasis - unopposed dilation of pupils
2. Inability to read up close - CN VII has what 2 autonomic functions?
-
-Lacrimal innervation
-Salivatory innervation -
CN VII - lacrimal:
-Preganglionic NCB location
-Route
-Postganglionic NCB location
-Route
-Target -
Pre NCB: superior salivatory nucleus in pons
Route: thru nervous intermedius and geniculate ganglion (both CN VII); via Greater petrosal n. to Nerve of Pterygoid canal
Post NCB: Pterygopalatine ganglion (attchd to V2)
Post route: Via zygomaticotemporal n (v2) and lacrimal nerve (v1)
Target: Lacrimal gland and mucosa of nasal cavity, nasopharynx, and palate. - What will injury to CN VII lacrimal function result in?
- Dry corneas
-
CN VII - salivary
-Preganglionic NCB location
-Route
-Postganglionic NCB location
-Route
-Target -
Pre NCB: superior salivatory nucleus
-Pre Route: thru nervous intermedius and geniculate ganglion (both VII); via Chorda tympani to join Lingual n. (v3)
-Post NCB: Submandibular ganglion (attached to v3)
-Post route: already there
-Target: submandibular and sublingual glands - Injury to salivary function of CN VII results in:
- failure to salivate at those glands.
-
CN IX
-Preganglionic NCB location
-Route
-Postganglionic NCB location
-Route
-Target -
Pre NCB: inferior salivatory nucleus
Route: exit brain w/ CN IX fibers, pass thru tympanic n and lesser petrosal n.
Post NCB: otic ganglion (attchd to V3)
Post route: runs w/ auriculotemporal n (of V3)
Target: parotid gland - Injury to salivary function of CN IX results in:
- failure to salivate at parotid gland.
-
CN X
-Preganglionic NCB location
-Route
-Postganglionic NCB location
-Route
-Target -
Pre NCB: Dorsal motor nucleus of CN X in medulla
Route: run with CN X
Post NCB: autonomic ganglia near or w/in target organ walls
Target smooth muscle and glands of GI tract, pulmonary, and cardiovascular systems - Purely sensory nerves: (3)
-
1, 2, 8
Olfactory
Optic
Vestibulocochlear - Sensory + motor nerves: (4)
-
5, 7, 9, 10
Trigeminal
Facial
Glossopharyngeal
Vagus - Purely motor nerves: (5)
-
3, 4, 6, 11, 12
Oculomotor
Trochlear
Abducent
Spinal accessory
Hypoglossal - Nerves associated w/ Special Senses: (6)
-
1, 2, 7, 8, 9, 10
I = olfactory = smell
II = optic = vision
VII = facial = taste (ant 2/3)
VIII = vestibulocochlear = balance and hearing
IX = glossopharyngeal = taste (post 1/3)
X = vagus = taste (epiglottis) - Cranial nerves passing thru cavernous sinus:
- 3, 4, 5 (1/2), 6
- Cranial nerves innervating extraocular muscles:
- 3, 4, 6
- Cranial nerves carrying preganglionic parasympathetic fibers:
-
3 (sphincter pupillae and ciliary muscles)
7 (lacrimal, submandibular and sublingual glands)
9 (parotid)
10 (smooth muscle of thorax and abdominal viscera) - Cranial nerves to which parasympathetic ganglia are attached:
-
V1 = ophthalmic - ciliary ganglion
V2 = maxillary - pterygopalatine ganglion
V3 = mandibular - otic and submandibular ganglia - Which cranial nerves pass thru the ethmoid bone?
- only one; olfactory CN I
- Which cranial nerves pass thru the sphenoid bone?
- 2,3,4,5,6
- Which nerves pass thru what holes in the sphenoid bone?
-
2 = optic canal
3, 4, V1, 6 = sup orb fissure
V2 = foramen rotundum
V3 = foramen ovale - Which cranial nerves pass thru the Temporal bone?
- 7, 8, 9, 10, 11
- Which nerves pass thru what holes in the temporal bone?
-
7 & 8 = internal acoustic meatus
9-11 = jugular foramen
11 = also thru foramen magnum - Which cranial nerves pass thru the occipital bone?
- only one; hypoglossal CN XII passes thru hypoglossal canal.