Neuro: Cranial Nerves Flashcards
How many cranial nerves come from the midbrain?
2
CN 3 and 4
How many cranial nerves come from the pons?
4
CN 5, 6, 7, 8
How many cranial nerves come from the medulla?
4
CN 9, 10, 11, 12
Why are cranial nerve 1 and 2 susceptible to MS disease
They are innervated by oligodendricytes instead of schwann cells due to location (they don’t leave the CNS)
What is the only sensory nerve that reaches the cortex WITHOUT going through the thalamus
olfactory
define anosmia
loss of smell
remember much information related to taste is olfactory in origin
Where does the optic nerve cross?
The optic chiasm
Note: the optic tract is between the chiasm and the brain
if a lesion occurs on a R optial nerve, what will the visual field look like?
right eye blind
if a lesion occurs at the optic chiasm, how is the visual field impacted?
loss of lateral visual fields on both eyes
the lateral fields (temporal) cross over at chiasm
If a lesion occurs on the R optic tract, how is the visual field impacted?
loss of left visual field on both eyes
the L temporal crosses over to R side and R nasal will stay ipsilateral, forming the tract together
What nerve is responsible for pupil constriction AND orienting head and eyes (Saccadic, reflex neck movement)
Oculomotor CNIII
if your optic nerve is intact, but your oculomotor nerve is impaired, will you see pupillary constriction?
no
oculomotor causes the constriction
if your R optic nerve is impaired, and you shine light into the right eye will you see constriction? what happens if you shine it in the L eye?
R eye = neither eye constricts (cant sense the light and send to brain)
L = both eyes constrict bc L eye still able to sense and send info to brain, allowing oculomotor to constrict both
The olfactory nerve exits from what foramen?
Cribiform plate
The optic nerve exits from what foramen
Optic canal
The occulomotor nerve exits what foramen
superior orbital fissue
The trochlear nerve exits what foramen?
Superior orbital fissure
The opthamalic branch of the trigeminal nerve exits from what foramen
superior oribital fissure
The maxillary branch of the trigeminal nerve exits from what foramen
foramen rotundum
the mandibular branch of the trigeminal nerve exits from what foramen
foramen ovale
The abducens nerve exits from what foramen?
superior orbital fissure
The facial nerve exits from what foramen?
auditory canal (Stylomastiod foramen)
The vestibulocochlear nerve exits from what foramen?
auditory canal (stylomastoid)
Glossopharyngeal nerve exits what foramen?
Jugular foramen
The vagus nerve exits through what foramen?
Jugular foramen
The spinal accessory nerve EXITS through what foramen?
Jugular Foramen
The spinal accessory nerve ENTERS the skull through what foramen?
Foramen magnum
The hypoglossal nerve exits the skull from what foramen?
hypoglossal canal
Damage to the R optic tract after the optic chiasm will cause….
L sided homonymous hemianopsia (Blind in the left visual field of both eyes)
Damage to an optic nerve between the optic chasm and the eyeball will cause…
Ipsilateral blindness (full blindness of the eye on that side in both visual fields)
Explain optic nerve pathway
- Photosensitive cells in retina
- optic nerve –> optic chiasm –> optic tract –> thalamus (lateral geniculate nucleus) –> primary visual cortex in occipital lobe
Optic nerve reflex: midbrain
-pupil constriction
-orienting head and eyes
(saccadic eye movement- superior colliculus, CN 3 and CN 4)
-reflex neck movement: tectospinal tract from superior colliculus nerve
Pupillary light reflex involves which cranial nerves?
optic (afferent) and oculomotor (efferent)
Explain pupillary light reflex
Dilation: SNS
Constriction: PNS
when light is shined into 1 eye there is normally direct constriction in same eye and consensual constriction in other.
complete interruption of optic nerve causes?
loss of pupillary light reflex and blindness
what muscles does the oculomotor nerve control?
4 extraocular muscles
-superior, inferior, medial rectus muscle
-inferior oblique (ER, up, abducts)
levator palpebrae superioris (elevates eyelids)
parasympathetic fibers of the oculomotor nerve are responsible for what?
ciliary nerve causes pupillary light reflex
PNS fibers of oculomotor cause what to accomodation reflex?
-pupil constriction
-curvature of lens increase more convex
-eye converges (B medial rectus)
external strabismus is
CN III issue
ipsilateral eye fixed in abduction
ipsilateral ptosis is
CN III issue
paralysis of upper eyelid
diplopia is
CN III issue
double vision
Ipsilateral pupil fully dilated is called
mydriasis
What nerve innervates the “superior oblique muscle” of the eye
Trochlear nerve; rotates eye toward nose (internal)
adducts and depresses eye
if someone has issues with CN IV, what might their symptoms be?
ipsilateral eye cannot look down
double vision
difficulty reading or descending stairs
head tilt to opposite side to compensate
what muscles does trigeminal innervate? what side would the jaw deviate to when closing if there was a lesion on the R?
innervates: massester, temporalis, medial/lateral pterygoids
deviate to the R because pterygoids do contralateral deviation, so if the right ones are weak, they couldn’t push to left and counter it
Do trigeminal nerve motor fibers cross?
no so fibers innervate muscles ipsilaterally
The orbicularis oculi does what action, and what is its innervation?
Closes eyes
-Facial nerve
describe the corneal blink reflex
trigeminal nerve
triggered by tactile stimulation of cornea –> consensual eyeblink response
The consensual blink response is activated by _______ (1st order neuron) and sent to the _______ (2nd order neuron) and passed through interneurons in the ________ to both ________ nerves to B orbicularis oculi to blink both eyes
Trigeminal ganglion
spinal Trigeminal nucleus
reticular formation
Facial Nerves
problem with a facial nerve will cause numbness of the ___ side of the face and mouth
same
trigeminal neuralgia
sharp shooting facial pain neuropathic pain set off by stimulation not normally painful
NO sensory loss
CN V clinical implications
numbness to same side of face and inside mouth
-jaw closure can still occur due to sufficient strength of opposite side, but jaw will deviate to weaker side due to unbalanced action of internal pterygoid of strong side
What muscle does CN VI innervate?
lateral rectus m (abducts)
what is the only muscle that moves eye laterally?
CN VI
What does damage to CN VI cause?
double vision
try to list the motor, parasympathetic, somatic sensory and special sensory of the facial nerve
motor fibers with cell bodies in facial nerve nucleus - eyes, lips, stapedius of ear
parasympathetic fibers of superior salivatory nerve - salivary but not parotid, lacrimal and nasal glands
somatic sensory fibers of trigeminal spinal nerve - tongue, pharynx, skin near ear canal
special - anterior 2/3 tongue to solitary
signals to/from CN VII have nuclei where?
pons, medulla, and upper SC
Cranial nerves are ____ motor neuron (PNS/CNS)
what condition does this mimic? how is it different than a stroke
cranial - lower, PNS
bells palsy (CN VII)
a stroke affects CNS, which affects UMNL, affecting the lower half of the face, not the whole half
What does the vestibular branch transmit info?
head position and movement
What kind of info does cochlear branch transmit?
hearing
The superior colliculus is for _____ whereas the inferior colliculus is for _____
Vision
Hearing
What does the vestibular apparatus contain?
utricle
saccule
3 semicircular canals
What is the fluid called inside of the vestibular apparatus?
Endolymph
What is the fluid called that separates the bony structures from the membranous labyrinth of the vestibular system?
Perilymph
Head movement causes movement of ____ which moves embedded hair cells to fire the vestibular branch of CN VIII
endolymph
Movement of the endolymph inside of the semicircular canals detects…
Rotational acceleration/deceleration
the utricle and saccule respond to head position relative to
gravity and linear acceleration/deceleration
What causes the depolarization of the cochlear nerve endings
Vibration of endolymph is detected by hair cells which depolarize and send signal to cochlear nerve endings to activate them
what three structures does the cochlear nuclei send information to?
reticular formation, inferior colliculus and medial geniculate body (thalamic relay station to primary auditory cortex)
RIM
what three cortical areas process auditory
primary auditory cortex
auditory association cortex (memories)
wenickes area
(language comprehension)
PAW
what happens with loss of hearing in one ear?
interferes with ability to locate sounds. normally timing of input from each ear is compared with location of sounds in space
CONDUCTIVE DEAFNESS
transmission of vibrations is prevented in the outer or middle ear (lots of ear wax or otitis media)
sensorineural deafness
damage of receptor cells or the cochlear nerve (less common)
Causes: internal acoustic trauma, ototoxic drugs, Menieres disease, acoustic neuroma
where is the cell bodies (vestibular ganglion) of the vestibular nerve?
internal auditory canal
Where does Vestibular branch transmit info from and to?
transmits info from hair cells of SCC, utricle, saccule to
1.vestibular nuclei in medulla and pons
2.flocculonodular lobe in CE
where are cell bodies of vestibular branch?
in vestibular ganglion within internal auditory meatus
vestibular system is considered CNS or PNS?
both; peripheral part= peripheral vestibular n and vestibular apparatus
Clinical implications of VIII?
vertigo, dizziness, nystagmus, ataxia, N/V
what does glossopharyngeal do? its a mixed nerve…
motor fibers - stylopharyngeus (swallowing)
parasympathetic fibers - salivary gland and carotid body and sinus
somatosensory - soft palate, pharynx, post tounge
gag reflex
Glossopharyngeal nerve motor fibers sent to?
stylopharngeus muscle used for swallowing
PNS fibers of VN IX sent to?
parotid salivary glands and carotid body/sinus (O2 and BP)
somatosensory fibers of CN IX sent to?
soft palate, pharynx, around ar, posterior 1/3 tongue
where is the info from the glossopharyngeal processed
in nucleus in medulla and upper cervical SC
what does CN IX contribute to afferent limb of?
gag and swallowing reflex
clinical implications of CN IX
-decreased salivation, some taste
-decreased or absent gag reflex or swallowing reflex
What cranial nerve controls peristalsis inside the esophagus
vagus nerve
Explain vagus nerve somatic motor to muscles, PNS fibers, general visceral sensory fibers
- somatic motor to muscle of larynx, pharynx, and palatoglossus
2.PNS motor fibers to decrease HR, constrict bronchi, increase digestion
3.general visceral sensory fibers from tongue to intestine
Vagus efferent or afferent part of gag and swallowing?
efferent
where are the cell bodies of vagus visceral afferents and PNS efferents?
- visceral afferents: inferior nucleus of vagus outside of brainstem
2.PNS efferents: nucleus ambiguous and dorsal motor nucleus of vagus in medulla
clinical implication of vagus?
unilateral lesion causes hoarseness and swallowing difficulties, poor digestion. uvula deviates contralaterally
What nerve handles the lips closing when you put food in your mouth?
Facial nerve
What nerve closes the larynx when you swallow?
Vagus
What nerve triggers the swallowing reflex (afferent)?
Glossopharyngeal
Where are the cell bodies of the spinal accessory nerve found?
Ventral horn of C1-C4
What nerve decreases HR, Constricts Bronchi, and increases digestion?
Vagus nerve
What nerve controls the efferent part of the gag reflex?
Vagus
Conductive deafness
Transmission of vibrations prevented in the outer or middle ear
What is Sensorineural deafness?
Damage to receptor cells or the cochlear nerve
damage to spinal accessory nerve causes?
weakness when turning head to side opposite of lesion and downward rotation of scapula
what does hypoglossal nerve innervate?
all intrinsic tongue muscle and 3/4 extrinsic tongue muscles
cell bodies of hypoglossal nerve are where?
nucleus of medulla
What cranial nerve involved in swallowing?
CN V,VII,IX,X
What nerves involved in speaking?
CN V,VII,X
True or false: Sensorineural deafness is less common than conductive deafness
True
What is dysarthria?
Poor control of speech muscles
-only vocal speech affected
can be CN or CNS related
Note: they still understand language
Damage to what nerve can cause dysarthria?
Hypoglossal
True or false: The dorsal root ganglion is a part of the CNS
False, it is part of the PNS
White matter tract vs column
Tract- bundle of axons with common destinaton
Column- Several tracts
Where are the cell bodies of efferent neurons found?
Ventral horn
Where are the cell bodies of afferent neurons found?
Dorsal root ganglion
What is epineurium
Fiberous sheath surrounding entire nerve
What is perineurium
Connective tissue wrapping around fascile of axons
What is endoneurium
connective tissue surrounding axon
LMN lesion of hypoglossal?
flaccid/paralysis/ atrophy of ipsilateral tongue muscle
UMN lesion of hypoglossal?
inactivity of contralateral tongue muscle so tongue deviates to side opposite of lesion
