lecture 17: CN VIII Flashcards
what are the three semicircular canals
anterior
posterior
lateral
which semicircular canal is in the horizontal plaen
lateral
what is the name of the enlargement at the end of each semicircular canal
ampullae
what are the 3 bones of ear
malleus
incus
stapes
which 5 aspects make up the vestibular system of the eat
lateral, anterior, posterior semi circualr canalas
utricle and saccule
what is the connection to the nasopharynx in the inner ear called
auditory tube (pharyngotympanic)
what is the auditory part of the inner ear called
cochlea
true or false, there are two vestibular ganglion/branches of the vestibular n
true
which semicircular canal is closest to outer ear
lateral
what makes up the vestibular apparatus
semicircular canals
otolith organs
what are the otolith organs
utricle and saccule
the ampulla contains cristae, what are they
sensory receptors
what do we use to sense where our head is in space and how it is movign
vestibular apparatus
the vestibular apparatus sits where in the skull
in the petrous part of the temporal bone
rotational acceleration of the head is detected by what
semicircular cancels (maximally activated by a particular plane)
rotational acceleration of the head in the sagittal plane is detected by what
anterior canal
rotational acceleration of the head in the horizontal plane is detected by what
lateral canal
rotational acceleration of the head in the frontal plane plane is detected by what
posterior cancel
linear acceleration and head tilt is dectected by
utricle and suckle
horizontal linear acceleration and head tilt is dectected by
utricle
vertical linear acceleration and head tilt is dectected by
saccule
jumping is detected by the utricle or saccule
saccule
walking is detected by the
utricel
nodding yes is detected by which canal
anterior canal
saying no is detected by which canal
lateral
enlargement (ampulla) in each semicircular canal contains modified BLANK cells
hair cells
what are the modified hair cells of in the ampulla
stereociliea and kinocilium
the modified hair cell projections of the ampulla are embedded in what
a gelatinous done
what is the purpose of having the the modified hair cell projections of the ampulla embedded in gelatinous dome
dome ensures they are firing in the same direction depending on the movement
what is the cupula
gelatinous done in which the sterocilia and kinocilium of the ampulla are embedded
movement of endolymph deforms the cupula true or false
true
movement of endolymph TOWARDS kinocilium means activation or inhibition
activation
movement of endolymph AWAY FROM kinocilium means activation or inhibition
inhibition
in which direction does the endolymph in the semicircular canals move with respect to movement of head
opposite (due to inertia)
what is the equivalent of the cupula in the otolith organs
macula
explain how movement is detected by semicircular canals
rotational acceleration of the head in one direction is detected by semicircular canals
the endolymph within the activated canal moves in direction opposite to head movement
endolymph movement will deform cupula (if toward kinocilium=activation)
what are the names of the carbonate crystals of the otolith organs
statoconia
explain how movement is detected by otolith organs
linear acceleration of the head and head tilt in one direction is detected by otolith organs
the statoconia/crystals move with gravity during movement
this movement distorts the gelatinous matrix (containing specialized hair cells)
distorts hair cells which sends signals through the nerve
primary sensory neurons of vestibular division of CN VIII synapse with hair cells where
in ampullae and maculae
true or false, the specialized hair cells in the ampullae and macula are considered to be primary sensory neurons
false,
primary sensory neurons of vestibular division of CN VIII synapse with hair cells
where are the cell bodies of primary sensory neurons of the vestibular ganglion located
in vestibular ganglion
the vestibular n joints which n to form the CN VIII
cochlear
the vestibulocochlear n enters the skull through where
)
internal acoustic meatus
the CN VIII enters the brainstem where
pontomedullary junction lateral to CN VII (cerebellopontine angle)
where do primary neurons of the vestibular division synapse with secondary neurons
in vestibular nuclei (special sensory)
the vestibular and cochlear nuclei are located at what level in brainstem
caudal pons (level of CN VI)and rostral medulla
what are the 4 divisions of the vestibular nuclear compex
superior
medial
lateral
inferior
where is the vestibular nuclear complex located (specific)
dorsolateral aspect of boundary between pons and medulla (floor of 4th ventricle)
vestibular nuclei is what type of nuclei
special sensory
what are the 4 areas of projection from the vestibular nuclei
1) MLF (control of eye movements)
2) cortex via thalamus (concious sense of position and movement)
3) cerebellum via inferior cerebellar peduncle (balance and coordination)
4) descending fibres (vestibulospinal pathways (adjust joint position and muscle tone)
explain the function of the projection to the MLF from the vestibular nuclei
1) MLF (control of eye movements)
=eyes stay fixated while head and body moves
explain the function of the projection to the cortex via the thalamus from the vestibular nuclei
2) cortex via thalamus (concious sense of position and movement)
explain the function of the projection to the cerebellum via inferior cerebellar peduncle from the vestibular nuclei
balance and coordination (vestibulocerebellar pathway)
explain the function of the projection to the descendinng fibers (vestibulospinal bathways) from the vestibular nuclei
(adjust joint position and muscle tone)
what is the purpose of the vestibuloocular reflex
rapid adjustment of eye movement with respect to head movement to keep gaze fixed on a target
what is the stimulus of the vestibuloocular reflex
a right or left horizontal rotation
explain the stimulus of the vestibuloocular reflex
eg: right horizontal rotation (sensed by hair cells in ampulla of lateral semicircular canal)
if you do right horizontal rotation, it is sensed by hair cells in ampulla of BLANK semicircular canal)
lateral
explain the afferent limb of vestibuloocular reflex
sensory signals travel via vestibular component of CN VIII to the vestibular nuclei
in the afferent limb of the vestibuloccular reflex, the sensory signals travel via what to the vestibular nuclei
via the vestibular component of CN VIII to the vestibular nuclei
in the afferent limb of the vestibuloccular reflex, the sensory signals travel via the vestibular component of CN VIII to what nuclei
vestibular nuclei
the vestibular nuclei is a branchial motor, visceral sensory or special sensory nuclei
special sensory
what is the function of the interneuron projecting from the vestibular nuclei to the contralateral abducens nucleus in the vestibuloocualr reflex
to connect the vestibular system into the horizontal gaze coordination
after the primary sensory neurons synapse in vestibular nuclei in vestibule occular reflex, thhe interneuron projects to what nucleus
abducens (contraletal)
after the primary sensory neurons synapse in vestibular nuclei in vestibule occular reflex, thhe interneuron projects to the abducens nucleus contralateral or ipsilateral
contralateral
explain the efferent limb of the vestibuloocualr reflex
a) abducens nucleus sends motor signals to lateral rectus ipsilateral
b) internuclear neurons project to the contralateral oculomotor nucleus via the MLF = sends motor signals to the medial rectus
what is the response oft he vestibulooccular reflex
eyes will track in the opposite direction
according to the vestibulocoualr reflex, if you do right horizontal rotation, the eyes will track in what direciton
opposite (ie. left direction)
if the vestibuloocualr reflex is trigged by left horizontal rotation of the head, which extraoccular muscle will be activated i the right eye
lateral rectus
if the vestibuloocualr reflex is trigged by left horizontal rotation of the head, which extraoccular muscle will be activated i the left eye
medial rectus
what are the two ways to test vestibuloocular reflex in comatose patients
oculocephalic reflex
caloric reflex
explain oculocepehalic reflex
eyelids open and head turned
=postive response = eyes will move opposite to direction of head rotation (reflex in tact)
=negative response = eyes will move in same direction as head rotation (reflex not intact)
explain a positive response according to the oculocephralic relfex
postive response = eyes will move opposite to direction of head rotation (reflex in tact)
explain a negative response according to the oculocephralic relfex
eyes will move in same direction as head rotation (reflex not intact)
explain the caloric reflex with cold water
irrigate lateral semicircular canal (because of horizontal direction)
=endolymph will move inferiorly, decreases the firing rate (mimics head turning contraltaealy), eyes move to ipsialtearl side (towards irrigated ear)
explain the caloric reflex with warm water
irrigate lateral semicircular canal (because of horizontal direction)
=endolymph will move superiorly, increases the firing rate (mimics head turning ipsilateral), eyes move to contralateral side (away from irrigated ear)
true or false, in a negative response to cold irrigation, the eyes will turn towards irrigated ear
false, a negative response the eyes would remain straight
true or false: the vestibular part of the inner ear is responsible for auditory
false, the cochlea is
explain the transition from sound wave to pressure waves (ie from tympanic membrane to scala vestibule)
sound wave comes and hits tympanic membrane
this vibration moves the malleus, incus and stapes
stapes pushes on the membrane of oval window which causes pressure waves in perilyphm of scale vestibule
explain the function of the stapes in terms of sound conduction
stapes pushes on the membrane of oval window which causes pressure waves in perilyphm of scale vestibule
what does the pressure waves in the peryiymph of scale vestibuli and tympani cause distortion of
causes distortion of cochlear duct (filled with endolymph) and basilar membrane on which the spiral organ rests
=stimulates hair cells (localization according to frequency)
cochlear duct contacts endolymph or perilymn
endo
spiral organ contains specialized hair cells who’s cell bodies are in what ganglion
spiral ganglion
explain the tonotopic arrangement of the basilar membrane
highest frequency at the base of basilar membrane (near oval window)
lowest frequency at the apex of basilar membrane
highest frequency of sounds disrupt what portion of the basilar membrane
at the base of basilar membrane (near oval window)
lowest frequency of sounds disrupt what portion of the basilar membrane at the apex of basilar membrane
at the apex of basilar membrane
true or false: highest frequency sounds disrupt the apex of basilar membrane
false, the base
true or false, all vestibular information coming from vestibular division of CN VIII has to go to cortex
false, there are 3 other projections (to MLF, to cerebellum and to descending fibers)
primary neurons of the cochlear division of CN VIII have sensory receptors where
hair cells near the basilar membrane (sit in spiral organ)
where are the cell bodies of primary neurons of the cochlear division of CN VIII
in spiral ganglion
the central processes of the primary neurons of the cochlear division of CN VIII project to what
ipsilateral cochlear nucleus
true or false: the central processes of the primary neurons of the cochlear division of CN VIII project to contralateral cochlear nucleus
false, ipsilateral
true or false: audition is a 4 neuron pathway
true
cochlear nucleis is located in what general region of the brainstem
caudal pons/rostral medulla (pontomedullar junction)
secondary neurons of the cochlear division of CN VIII project to what
bilateral inferior colliculi (mostly contralateral)
secondary neurons of the cochlear division of CN VIII project to ipsilateral or contractual inferior collic
bilateral (but mostly contralateral)
cell bodies of secondary neurons of the cochlear division of CN VIII are located where (what ganglion)
cochlear
the decussation going from the ipsilateral cochlear nuclei to the contralateral inferior colliculi in the cochlear pathway is called what
acoustic stria
which neuron i the cochlear division pathway decussates
secondary (in acoustic stria)
cell bodies of tertiary neurons of the cochlear division of CN VIII are located where
inferior colliculus
cell bodies of quaternery neurons of the cochlear division of CN VIII are located where
thalamus (MGN)
after synapse between secondary and tertiary neurons, the tertiary neurons of the cochlear division of CN VIII send information where
to ipsilateral medial geniculate nucleis
after synapse between secondary and tertiary neurons, the tertiary neurons of the cochlear division of CN VIII send information to ipsilateral or contralateral medial geniculate nucleis
ipsialtrals
superior or inferior colliculi is important for audition
inferior
what thalamic nucleus is important for the cochlear pathway of audition
medial geniculate nucleus
after synapse in thalamus, the quaternary neurons of the cochlear division of CN VIII project to where
primary auditory cortex (superior and transverse temporal gyri)
where is the auditory cortex primary
in the temporal lobe (transverse and superior temporal gyri)
true or false, in the cochlear division of CN VIII, information must pass through the corona radiate and internal capsule
false, does not need to pass there because we are saying below the lateral fissure (location of the primary auditory cortex)
what are the two structures organized in a tonotopic manner
basilar membrane of cochlear and auditory cortex
what is the tonotopic arrangement of the primary auditory cortex
high frequency = more medial (closest to insula)
low frequency = more lateral
in tonotopic arrangement of the primary auditory cortex, high frequency sounds are where
more medial (closest to insula)
in tonotopic arrangement of the primary auditory cortex, low frequency sounds are where
lateral
true or false: the cochlear nucleus is a special sensory
true
conductive hearing loss involves what parts of ear
outer and or middle
(ex: issue with tympanic membrane or ossicles)
conductive hearing loss causes
ear infection, excess earwax, ruptured ear drum, ossicle issue)
conductive hearing loss is alsways permanent
false, can be transcient
true or false: neural hearing loss involves difficulty actually conducting the sound waves into the cohclear
false, thats conductive
neural hearing los involves what part of the era
inner ear (esp sterociliea)
is neural hearing loss transient or permanent
permanent but treatable
what are the causes of neural hearing loss
hereditary factors, head injury, excessively loud sounds, infection
what are the two tests to differentiate between conductive and neural hearing loss
rinne test and weber test
rinne test is used to test what
checking conduction (if it is gonna be neural or conductive)
weber test is used to test what
localization (whether the right or left ear is affected)
in normal individuals, you should be able to hear the sound of tuning fork thru air or bone longer
air (2 times longer)
in neural hearing loss, sound conduction in air is longer than bone or shorter
longer
in normal hearing, sound conduction in air is longer than bone or shorter
longer
in condition hearing loss, sound conduction in air is longer than bone or shorter
bone
during the weber test, if a person has no hearing loss, where will the hear the tuning fork best
midline
during the weber test, if a person has neural hearing loss, where will the hear the tuning fork best
normal ear (sound localizes to good ear)
during the weber test, if a person has conductive hearing loss, where will the hear the tuning fork best
affected ear (sound will localize to affected ear (going thru bone))
be able to explain rinne and weber test
explain why sound conduction is better in bone than air for people with conductive hearing loss
sound wave is bypassing problematic parts of outer and middle ear)
individual does rhine test and finds out he has conductive hearing loss, during weber, which ear will they ear it louder on and what does that mean
will hear it louder on affected ear (conductive hearing loss in ear that is louder)
individual does rhine test and finds out he has neural hearing loss, during weber, which ear will they ear it louder on and what does that mean
will hear it louder in normal ear (neural hearing loss in opposite ear)
what is an acoustic neuroma
benign slow progressing tumour of glial cells that myelinated the vestibular division of CN VIII (rare cases also affect cochlear)
the acoustic neuroma expands into what
the cerebellar pontine angle
the acoustic neuroma expands into the cerebellar pontine angle, compressing what nerves in the visinity
Cn VIII
CN VII
CN Vw
what are the expected deficits of an acoustic neuroma pressing on CN V
loss of somatosensation to dermatomes of face V1,2,3
loss of motor innervation to muscles of mastication (ipsilaterally)
what are the expected deficits of an acoustic neuroma pressing on CN VII
loss of sensation from skin of external ipsilateral ear, taste from anterior 2.3 of tongue, loss of motor innervation to muscles of facial expression (whole ipsilateral face) and loss of lacrimation and reduced saliva
what are the expected deficits of an acoustic neuroma pressing on CN VIII
loss of balance and loss of vestibulocular reflex in one direction (ipsilateral to lesion)
problems with balance and hearing (if affects cochlear division)
what is the associated foramen of the vestibulocochlear n
internal acoustic meatus
true or false
