NEURO LEC 8: 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 option 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)
what muscles does the oculomotor nerve control?
4 extraocular muscles
levator palpebrae (elevates eyelids)
parasympathetic fibers of the oculomotor nerve are responsible for what?
ciliary nerve causes pupillary light reflex
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
adducts and depresses eye
if someone has issues with CN IV, what might their symptoms be?
double vision
difficulty reading or descending stairs
head tile to opposite side
what is the only cranial nerve that exits from the dorsum of the brainstem?
trochlear
what muscles does trigeminal innervate? what side would the jaw deviate to when closing if there was a lesion on the R?
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
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
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 in order to close both eyes
Trigeminal ganglion
spinal Trigeminal nucleus
reticular formation
Facial Nerves
aka when something is in one eye both eyes will blink
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
What muscle does CN VI innervate?
lateral rectus m
try to list the motor, parasympathetic, somatic sensory and special sensory of the facial nerve
motor - eyes, lips, stapedius of ear
parasympathetic - salivary, lacrimal and nasal glands
somatic sensory - tongue, pharynx, skin near ear canal
special - anterior 2/3 tongue to solitary
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
The superior colliculus is for _____ whereas the inferior colliculus is for _____
Vision
Hearing
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)
PAW
CONDUCTIVE DEAFNESS
transmission of vibrations is prevented in the outer or middle ear (lots of ear wax)
sensorineural deafness
damage of receptor cells or the cochlear nerve (less common)
where is the cell bodies (vestibular ganglion) of the vestibular nerve?
internal auditory canal
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
afferent gag reflex
where is the info from the glossopharyngeal processed
in nucleus in medulla and upper cervical SC
What cranial nerve controls peristalsis inside the esophagus
vagus nerve
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
True or false: Sensorineural deafness is less common than conductive deafness
True
What is dysarthria?
Poor control of speech muscles
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
which CNs are parts of CNS?
1 AND 2
internerons - PNS or CNS?
CNS
What is epineurium
Fiberous sheath surrounding entire nerve
What is perineurium
Connective tissue wrapping around the fascicle of axons
a peripheral nerve contains several fascicles
What is endoneurium
connective tissue surrounding each axon in a fascicle
Why is movement essential for nerve health?
movement promotes BF through the nerve and flow of the axoplasm through the axons
axoplasm - transports chemicals b/w axons and cell bodies, regulates cell’s fxn
What happens to axoplasm when we are stationary?
it thickens and becomes more resistant to flow
A alpha fibers are the ____ (speed) and send what info?
What fiber is the slowest?
a alpha do muscle spindles and GTO, FASTEST (proprioception and motor?)
C fibers that do pain are the slowest
somatic sensory special:
visceral sensory special:
hearing, equilibrium and vision
taste and smell (think internal)
if disc is impinging on spinal nerve, C6-C7 disc impinging on __ would be stated
C7
where are spinal nerves formed? what space
intervertebral foramen
How would symptoms be different if you had a lesion on C6 spinal nerve root vs the median nerve?
with the root lesion, you would just have weakness bc other nerve roots contribute to the plexus
the peripheral nerve lesion would cause complete loss to the muscle beign innervated
each muscle limb receives its nerve supply from > 1 spinal nerve
damage to 1 spinal segment or root can/cannot completely paralyze any limb muscle
CANNOT
lumbar plexus carries efferent to muscles of
carries afferent sensory from what regions
motor - anterior pelvis, anterior medial thigh
afferent - skin of ant pelvis, medial and anterior thigh and medial lower leg
Lumbar plexus is nerve roots _ - __
Sacral is __ to __
L1-L4
L5-S4
sacral plexus efferent and afferent locations
efferent to posterior pelvis and posterior thigh and post lower leg and foot
afferent to skin of same areas
polyneuropathy
distal, symmetric distribution
glove and stocking, diabetes?
multiple mononeuropathy
multifocal random, asymmetric involvment of indiv. nn
Traumatic myelinopathy is mono/poly, is due to ___ and can have a ____ recovery
an example would be
mononeuropathy
repeated mechanical pressure that can occlude BF and damage myelin
full recovery
carpal tunnel
traumatic axonopathy is mono/poly, is when the ___ is damaged but the ___ is intact, meaning the nerve can ____
examples would be
mononeuropathy
axon
shwann cells/myelin
regrow at 1mm/day
crush injuries or closed fracture
Severance of a nerve has ___ prognosis
poor
polyneuropathy is ____ involvement of sensory, motor, and autonomic fibers and progresses from ___ to ____
symmetric
distal to proximal (stocking and glove)
what is meant that polyneuropathy is “length dependent”
longer fibers are attacked first
first symptoms of polyneuropathy tend to be
sensory loss/dysfunction
small fibers first - pain, temp, numbness, dysthesias
What is Guilain Barre Syndrome (acute inflammatory demyelinating polyradiculoneuropathy)
inflammatory demyelinating syndrome that typically occurs after viral infection causing more motor than sensory problems, distal to proximal
can affect respiratory muscles - need ventilator
good prognosis
PNS dysfinction muscle tone is
CNS dysfunction muscle tone is
PNS - hypotonia
CNS - hypertonia
Muscle atrophy is ___ with PNS dysfxn and ___ with CNS dysfxn
rapid for PNS
slow for CNS
PNS dysfxn:
NCV is
DTRs are
CNS dysfxn:
NCV is
DTRs are
PNS
NCV is decreased
DTRs are decreased/absent
CNS
NCV is normal
DTRs are increased or normal
