Cranial Nerves Flashcards
From First Lecture of CNs
Describe the fxn of olfactory n.
smell
Describe the connection of olfactory n. to the brain.
enters anterior frontal lobe via cribiform plate of ethmoid bone
Describe the fxn of optic n.
vision
Describe the connection of optic n. to the brain
originates in retina, to diencephalon, to optic chiasm/optic tract
Describe the fxn of oculomotor n.
moves eye up, down, medially
raises upper eyelid
constricts pupil
adjusts shape of lens
Describe the connection of oculomotor n. to the brain
midbrain
Describe the fxn of trochlear n.
moves eye medially and down
Describe the connection of trochlear n.. to the brain
midbrain below inferior colliculi
Describe the fxn of trigeminal n.
facial sensation, chewing, sensation from TMJ joint
Describe the connection of trigeminal n.. to the brain
pons
Describe the fxn of abducens n.
abducts eye
Describe the connection ofabducens n. to the brain
pontomedullary jxn
Describe the fxn of facial n.
facial expression, closes eye, tears, salivation, taste (anterior 2/3 of tongue)
Describe the connection of facial n.. to the brain
pontomedullary jxn
Describe the fxn of vestibulocochlear n.
sensation of head position relative to gravity and head movement; hearing
Describe the connection of vestibulocochlear n. to the brain
pontomedullary jxn; exits posterior cranial fossa via internal acoustic meatus
Describe the fxn of glossopharnygeal n.
swallowing, salivation, taste (posterior 1/3 of tongue)
Describe the connection of glossopharnygeal n. to the brain
medulla; postolivary sulcus
Describe the fxn of vagus n.
regulates viscera, swallowing, speech, taste
Describe the connection of vagus n. to the brain
medulla; postolivary sulcus
Describe the fxn of accessory n.
elevates shoulders, turns head
Describe the connection of accessory n. to the brain
SC and medulla; postolivary sulcus
Describe the fxn of hypoglossal n.
moves tongue
Describe the connection of hypoglossal n. to the brain
medulla; preolivary sulcus
Which CN’s are bipolar ganglion cells?
I, II, VIII (special sensory nerves)
Which nerve is part of CNS?
CN II
Which neurons can undergo mitosis?
Olfactory (CNI)
Which CN has central fibers that run a few mm in length and connect extensively with limbic system?
Olfactory (CNI) - smells can evoke memory, emotions
How is Olfactory (CNI) tested?
familiar odors
What typically causes lesions of Olfactory (CNI)?
facial fractures
Test visual fields for which nerve lesion?
CN II
Some fibers from each optic nerve cross at which strucutre?
optic chiasm
Where are motor and sensory nuclei of trigeminal n. located?
rostral pons
What are the 3 divisions of CN V?
V1: ophthalmic
V2: maxillary
V3: mandibular
How does V1: ophthalmic exit middle cranial fossa?
to orbit through superior orbital fissure
How does V2: maxillary exit middle cranial fossa?
to deep face through foramen rotundum
How does v3: mandibular exit middle cranial fossa?
to deep face through foramen oval
V3 provides innervation to
MOTOR mastication (masseter, temporalis, medial/lateral pterygoids
CN V supplies sensation to which areas?
face and part of head
ID the condition characterized by brief periods of intense nerve pain with unknown etiology.
tic douloureux = trigeminal neuralgia
tic douloureux = trigeminal neuralgia treatment?
can usually be treated pharmacologically or surgically (nerve root cut to remove all sensation to area).
Describe the corneal blink reflex
touch cornea (V1) with cotton, normal response is eye blink
What does orneal blink reflex test?
CN V and CN VII
Describe the jaw jerk reflex
analogous to DTR; tap jaw with reflex hammer
normal response is minimal/absent; reflexive response is contraction to close the jaw
If UMN Lesion, how would pt respond to jaw jerk reflex?
reflexive response is contraction to close the jaw; loss of inhibition of reflex
Loss of sensation in face and head, loss of corneal blink reflex, loss of muscle of mastication with which CN lesion?
CN V
usually one division implicated, unless cortical stroke affects all 3
Where is the facial n. nucleus located?
caudal pons
Which CN’s have parasympathetic innervation?
III, VII, IX, X
Which nerve innervates submandibular, sublingual, and lacrimal glands?
CN VII Facial N.
parasympathetic innervation to glands
What is Bell’s Palsy?
LMN lesion which results in paralysis of muscles of facial expressions (etiology unknown)
What is primary sign of Bell’s Palsy?
can’t close the eyes- loss of corneal blink reflex
Also, loss of taste to anterior 2/3 of tongue
What are the two divisions of CN VIII?
vestibular and cochlear
Where are vestibular nuclei located?
lateral recess of 4th ventricle in caudal pons and rostral medulla
Where does the VIII nerve end? (bony landmark)
ends in petrous portion of temporal bone where it divides into vestibular and cochlear divisions
What is the fxn of vestibular system?
regulates posture/equilibrium responses; coordinates eye movement with head movement
What are the features of the peripheral vestibular apparatus?
posterior, lateral, anterior semicircular canals; utricle, saccule
What is the fxn of the peripheral vestibular apparatus?
detect movement of the head in space and the force of gravity (can detect movement in any direction because of diverse orientations)
What fills the canals and the utricle and saccule?
endolymph
Describe the basic mechanism of AP generation in peripheral vestibular apparatus.
movement sets endolymph in motion, causes hair to “bend”, causes vestibular nerve endings to depolarize
What are 4 outcomes due to lesion of vestibular division?
loss of equilibrium
nystagmus
vertigo
nausea
What is nystagmus?
rhythmic beating of the eyes
What is one test for lesion of vestibular division?
caloric test (water irrigation at various temps to ID nystagmus presence); No nystagmus indicates lesion
How do sound waves travel from air to cochlea?
waves through air vibrate tympanic membrane, transfer to malleolus, incus, stapes, oval window, cochlea.
Describe the cochlea
fluid filled structure which contains organ of corti
Describe organ of corti and AP generation
surrounded by endolymph; responds to vibrations as hair cells in the organ of corti to bend and depolarizes afferent fibers of cochlear division of CN VIII
Lesions of cochlear division can cause 2 issues
tinnitus
deafness
What kind of dearness is decreased hearing due to nerve damage?
nerve deafness
What kind of deafness is caused by middle ear problems?
conduction deafness (sound waves are not conducted through air)
Describe Rinne’s test
tuning fork held against mastoid until no longer heard (tests NERVE) then placed in front of ear (tests CONDUCTION)
What is a normal response to Rinne’s test?
air conduction better than bone so pt should still hear the tuning fork when it is placed in front of ear
With air conduction deafness, how does Rinne’s test present?
can hear sound only through direct vibration of bone to stimulate nerve
Describe Weber’s test
tuning fork held over vertex of skull
What is a normal response to Weber’s test?
heard equally in both ears
What is abnormal response to Weber’s test?
conduction deafness: louder in AFFECTED ear
nerve deafness: louder in UNAFFECTED ear
Where is glossopharyngeal nucleus located?
rostral medulla
Lesion of CN IX presents as loss of (2):
gag reflex (loss of afferent limb of reflex) taste on posterior 1/3 of tongue
Vagus nucleus is located where?
in rostral medulla enar dorsal motor nucleus of vagus
Vagus exits posterior cranial fossa via
jugular foramen
Vagus has __ sensory ganglia located just outside of skull, glossopharyngeal has ___. (#s)
vagus - 2
glossopharyngeal - 1
Which nerve has taste afferents on epiglottis?
vagus!
Bilateral lesions of vagus nerve are usually ______.
fatal vagus has extensive central connections with respiratory and cardiovascular centers
Unilateral lesions of vagus nerve result in?
pharyngeal muscle weakness resulting in dysarthria (speech) and dysphagia (difficulty swallowing)
Which nerve(s) are tested with gag reflex test?
CN IX glossopharyngeal and X vagus
Loss of gag reflex indicates loss of _______ limb.
efferent
How can you test vagus?
speech, swallowing, uvula sideways movement, gag
How do you test accessory n?
Traps and SCM; weakness in ipsilateral muscles may indicate lesion
Cervical component/spinal portion of accessory nerve consists of which levels?
C2-C5/6
Cranial root of accessory n. innervation and final branching?
innervates some muscles of pharynx and eventually travels with vagus nerve
Where is the hypoglossal nucleus located?
rostral medulla
What innervates skeletal muscles of the tongue?
hypoglossal n.
Unilateral lesion of hypoglossal n.?
inability to protrude tongue in midline, tongue deviates to IPSILATERAL side as lesion
Bilateral lesion of hypoglossal n.?
dysphagia (difficulty swallowing) and difficulty eating
How do you test hypoglossal n.?
swallowing eval and tongue motion
Occulomotor n. is associated with which area of the brain?
Midbrain
What part of NS passes through tentorial notch and is vulnerable to compression against edge of notch with increased intracerebral pressures?
midbrain
Nerves that are pure MOTOR have nuclei that are located where?
medially!
