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AUDE 5160 > auditory vestibular system - central auditory nervous system > Flashcards

auditory vestibular system - central auditory nervous system Flashcards

1
Q

what does the middle ear serve as

A

impedance matcher
-remember the area difference between TM and stapes footplate, lever action and buckling of TM

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2
Q

what stimulates the organ of corti

A

traveling wave

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3
Q

is the ear canal the same length at the floor and ceiling

A

no, the floor is longer

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4
Q

how many layers of tissue is the TM

A

technically 4 layers
-continuous of skin from canal, radial fiber mesoderm, concentric circular fiber mesoderm, and continuous with mucous membrane of middle ear

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5
Q

how many row’s are there of each hair cell’s within the organ of corti

A

single row of inner, multiple of outer

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6
Q

how do the hair cells get stimulated

A

by the sterocilia getting stimulated

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7
Q

structures of the CANS

A

8CSLIMA
-from CN 8 to the cortex

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8
Q

what structures are part of the 8CSLIMA

A

cranial nerve 8, cochlear nucleus, superior olivary complex, lateral lemniscus, inferior colliculus, medial geniculate nucleus, A1 (primary auditory cortex)

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9
Q

CN 8

A

goes into brainstem
-enters at cerebellopontine angle (CPA)
-starting point of the CANS

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10
Q

cochlear nucleus (CN)

A

first station for processing auditory information in the brainstem
-monaural or ipsilateral at this level
-gets information from CN8 and begins processing

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11
Q

3 division of the cochlear nucleus

A

anterior ventral cochlear nucleus (AVCN), posterior ventral cochlear nucleus (PVCN), and dorsal cochlear nucleus (DCN)

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12
Q

what division is superior?

A

dorsal cochlear nucleus

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13
Q

3 fibers going off the CN divisions

A

ventral acoustic stria (down), intermediate stria (middle), dorsal stria (top)
-DIVe down (for direction)

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14
Q

direction of the ventral acoustic stria

A

from AVCN to join with the contralateral SOC and LL nucleus

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15
Q

direction of the intermediate stria

A

from PVCN to contralateral SOC

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16
Q

direction of the dorsal stria

A

from DCN to contralateral SOC

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17
Q

what does the cochlear nucleus do in terms of the cochlea?

A

preserves frequency mapping (tonotopic organization)

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18
Q

how are frequencies arranged within the cochlear nucleus

A

low are ventrolateral, high are dorsomedial

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19
Q

superior olivary complex (SOC)

A

gets information from the stria’s
-first level of the CANS to receive binaural input
-localization

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20
Q

2 divisions of the superior olivary complex

A

lateral and medial

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21
Q

lateral superior olive

A

received and processes high frequency information, localization of sounds based on interaural intensity differences
-high frequency and intensity

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22
Q

how does the lateral superior olive receive input

A

from ipsilateral AVCN and contralaterally from the AVCN and PVCN

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23
Q

how does the lateral superior olive have impacted time integrity

A

due to an extra synapse at the nucleus of trapezoid body

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24
Q

medial superior olive

A

receives and processes predominantly low frequencies, localization of sounds based on temporal cues
-low frequency and timing

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25
Q

how does the medial superior olive receive input

A

directly from the CN of both sides

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26
Q

lateral lemniscus (LL)

A

lateral bundle of axons
-from CN to IC
-tonotopicity
-commisure of probst

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27
Q

commisure of probst

A

connection across midline between both of the nuclei of lateral lemniscus

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28
Q

2 nuclei of the lateral lemniscus

A

ventral nucleus (VNLL) and dorsal nucleus (DNLL)

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29
Q

reticular formation

A

center core of the brainstem
-LL adds redundancy when it goes through here

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30
Q

inferior colliculus (IC)

A

obligatory relay station of the ascending auditory pathway (it has to stop here)
-largest of the brainstem nuclei

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31
Q

what are the inferior colliculus visible as

A

rounded humps

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32
Q

how does the inferior colliculus receive input

A

from contralateral IC

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33
Q

two major nuclei in each IC

A

central nucleus (core) and pericentral nucleus (belt)

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34
Q

what information does the central nucleus (core) carry

A

purely auditory fibers

35
Q

what information does the pericentral nucleus (belt) carry

A

somatosensory (sensations from the body) and auditory fibers

36
Q

brachium of the inferior colliculus

A

large tract projecting ipsilateral to the medial geniculate body in the thalamus
-fibers going into the thalamus from the inferior colliculus

37
Q

medial geniculate body (MGB)

A

group of nucleus in the thalamus
-last station in CANS prior to areas in the cortex
-gudden’s commissure
-leaves through auditory radiations

38
Q

3 divisions of the MGB

A

ventral, dorsal, and medial

39
Q

ventral MGB

A

responsive primarily to acoustic stimulus
-transmits directly to A1

40
Q

dorsal MGB

A

response to somatosensory and acoustic information
-projects to association areas of A1

41
Q

medial MGB

A

responsive to somatosensory and acoustic stimulation
-multisensory arousal system

42
Q

internal capsule

A

within the thalamus and is where items pass through
-all fibers are coming up into the thalamus and are trying to pass though
-all fibers gets packed tightly here
-corona radiate are where axons leave and radiate around the crown

43
Q

gudden’s commissure

A

connects the two thamalus geniculate bodies

44
Q

A1

A

primary auditory cortex

45
Q

why do auditory systems have built in redundancies

A

information comes up and crosses over in multiple places so if there was a lesions in one areas, there would still be the potential to continue getting to the cortex
-so many ipsilateral and contralateral pathways/commissures that it is bound to get to the cortex in one way or another

46
Q

how do redundancies impact audiologic testing

A

it makes our testing harder because the redundancy of the ear causes pure tones and word recognition to get through easier, which means there has to be an increase of difficulty in our testing

47
Q

vestibular schwannoma (acoustic neuromas)

A

a tumor formed from myelin of the superior and inferior vestibular nerves
-tumor can sit and be impactful of CN 7/8
-vascular supply can be impacted as well as nerve functions based on what nerves are impacted

48
Q

what is used during an MRI to find a vestibular schwannoma

A

an enhancement agent
-makes the tumor light up so we can tell where it is

49
Q

blood supply to the AVS

A

labyrinthine artery branches from AICA or the basilar artery

50
Q

labyrinthine artery

A

divides into common cochlear artery and anterior vestibular artery

51
Q

pathway of the common cochlear artery

A

comes from the labyrinthine artery to the common cochlear artery to both the posterior vestibular artery and the main cochlear artery
-posterior vestibular artery goes to PS
-main cochlear artery goes to the cochlea

52
Q

pathway of the anterior vestibular artery

A

comes from the labyrinthine artery to the anterior vestibular artery and goes to LSU

53
Q

LSU on top PS

A

lateral ampullary nerve, superior ampulalry nerve, utricle nerve, posterior ampullary nerve, and saccule nerve
-where artery goes to

54
Q

temporal bone fractures facts

A

this bone is a tough pyramid shaped bone but can fracture with force
-can be bilateral
-3:1 ratio male to female
-longitudinal, transverse, and oblique

55
Q

longitudinal fracture

A

parallels the long axis of the petrous portion of the bone
-from lateral to medial (long way)
-tears in skin of canal and TM
-CHL due to middle ear/ossicular disruption

56
Q

transverse fracture

A

perpendicular down through the petrous portion
-vertical direction
-SNHL
-TM could show blood in it

57
Q

oblique fracture

A

mixed, but most similar to longitudinal fracture

58
Q

new classification of temporal bone fractures

A

otic capsule sparing, otic capsule disrupting
-otic capsule refers to the bony labyrinth of the inner ear

59
Q

otic capsule sparing

A

more outer and middle ear involvement
-temporoparietal blow, FN paralysis, CHL or mixed, CSF leak not likley

60
Q

otic capsule disrupting

A

damage to labyrinth, IAC, or other internal aspect
-occipital blow, FN paralysis, SNHL, CSF leak more likely

61
Q

battle sign with temporal bone fracture

A

bruising behind the ear
-good sign of a fracture
-post auricle bruising

62
Q

diagnosis of temporal bone fracture

A

-look at reflexes and facial nerve function
-inspection of ear and temporal bone
-bloody otorrhea (ear drainage) and hemotympanum (blood or bruise within TM) are common)
-CT or high resolution CT scan
-check for vertigo, dizziness, and presences of nystagmus

63
Q

treatment of temporal bone fracture

A

surgery, decompression, corticosteroids, bed rest and not straining
-will treat HL and remaining balance issues later

64
Q

extradural hematoma

A

blood or bruising that is outside the dura (between dura and bone)
-looks more like the shape of a lemon due to the dura being forced away from the bone

65
Q

subdural hematoma

A

blood or bruising that is lower than the dura (subarachnoid where CSF is)
-looks more like a banana as it is making the space wider and following the curve of the bone

66
Q

transduction in the hair cells

A

sterocilia move as a whole bundle, special tip links stretches and deflection occurs towards the tallest sterocilia, opens the channels, endolymphy flows inward and depolarizes the cell, causes voltage gated calcium channels to open, triggers release of NT on the CN 8 ending

67
Q

hair cells with their sterocilia are ______________

A

specialized mechanoreceptors

68
Q

inner hair cells

A

main sensory receptor
-receives around 90-95% of CN 8 fibers
-1 IHC synapses to many neurons CN 8 fibers (diverges)

69
Q

outer hair cells

A

amplifiers
-receives only around 5-10% of innervation from afferents
-many OHC synapses to one neurons of CN 8 fibers (convergent)

70
Q

unipolar neuron

A

one cell body and one part coming off of it

71
Q

bipolar neuron

A

one cell body and two parts coming off of it
-piece coming off each side
-CN 8 is this type

72
Q

multipolar

A

multiple dendrites, an axon, and various branches

73
Q

pseudo-unipolar

A

mix between unipolar and bipolar in a way
-dendrite side and axon side
-splitting and going in two places

74
Q

CN 8 firing

A

when stimulated by sufficient NT, AP is generated, sodium influx to depolarize based on opening of voltage gated ion channels, followed by potassium outflux to repolarize

75
Q

AP key factors

A

voltage gated ion channels, all or non depolarization, self propagating, moves forward only, jumps from node to node

76
Q

summary of encoding by CN 8 (how does it encode frequency and intensity?)

A

frequency : tonotopic organization and phase locking
intensity : rate of firing of AP, how many fibers are firing, which fibers are firing

77
Q

description of rate of firing

A

AP’s are all or none, so therefore there are no small or large AP signals. this leads to intensity being encoded by a soft sound equalling a slower AP firing rate and a louder sound having a faster AP firing rate

78
Q

description of which fibers are firing

A

each fiber fires for a certain range as not every fiber can fire for 0-120 dB

78
Q

description of how many fibers are firing

A

the louder a sound is leads to the stimulation of more BM so more hair cells will get stimulated and a larger bunch of nerves will fire

79
Q

where within CANS does tonotopic organization occur

A

superior olivary complex, lateral lemniscus, inferior colliculus, medial geniculate body, A1

80
Q

what CANS pathway is dominant?

A

contralateral is more dominant

81
Q

what are the auditory ganglia?

A

spiral ganglia

82
Q

what are the vestibular ganglia?

A

scarpa’s ganglia

83
Q

how does a sound get to the cortex

A

-acoustic energy meets pinna meets ear canal as resonator
-turns into a mechanical vibration in ME with impedance matching
-pushes on oval window which sends hydraulic wave through cochlea with pressure release in round window
-receptor potential : sterocilia will be sheared, short to tall will excite causing potassium to rush in to depolarize, calcium flows in and triggers NT to dump out
-action potential : opens voltage gated ion channels, sodium rushes in to depolarize spot on nerve, potassiums channels open and cell will reset itself
-CANS pathway will occur upon stimulation of CN 8
-8CSLIMA

AUDE 5160 (23 decks)

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