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CDS 4300 exam 2 > inner ear > Flashcards

inner ear Flashcards

1
Q

3 parts of the cochlea

A
  • scala vestiboli
  • scala media
  • scala tympani
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2
Q

labyrinth

A

within the bony walls of the cochlea, complex network of delicate membranes
-connecting pathways in the petrous portion of the temporal bone

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3
Q

transduction

A

converting acoustical-mechanical energy into electro-chemical energy

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4
Q

cochlear functions

A

-transduction and frequency analysis

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5
Q

frequency analysis

A

breaking sounds up into its component freqencies

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6
Q

vestibule

A
  • middle ear connects with the inner ear through the oval window
  • behind the oval window is the vestibule
  • leads to the hearing part of the ear, cochlea
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7
Q

general anatomy of inner ear

A
  • tube-shaped and separated into 3 sections by thin membranes
  • from the beginning of the cochlea at the base to the apex at the outer end, the tube curves several time around the modiolus
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8
Q

modiolus

A

bony center of the cochlea

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9
Q

scala

A

the cochlea is separated ito 3 portions or ….

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10
Q

reissner’s membrane

A

separates the scala vestibule from the scala media

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11
Q

scala vestibuli is filled with what kind of fluid?

A

perilymph

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12
Q

scala media is filled with what?

A

endolymph

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13
Q

what does the basilar membrane spirit?

A

scala media and scala tympani

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14
Q

what is the scala tympani filled with?

A

perilymph

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15
Q

helicotrema

A

small opening at the apical end of the cochlea

-forms connection b/w the scala tympani and scala vestibuli

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16
Q

stria vascularis

A

contributes to cochlear function, forms the lateral border of the scala media

  • recieves generous supply of blood and has high rate of metabolism
  • serves as a pump for the transporting K+ into endolymph, the cochlear fluid within the scala media
  • plays crucial role in producing energy used by other structures- outer hair cells
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17
Q

endocochlear potential

A

sizeable positive electrical charge within the scala media in comparison to the electrical state in other portions of the cochlea

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18
Q

basilar membrane

A

narrow at the base and wider at the apex

-each movement of the stapes footplate produces vibration of the BM that travels away from the footplate

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19
Q

base of the BM

A

narrow
stiffer
high frequencies

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20
Q

apex of the BM

A

wider
looser
lower frequencies

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21
Q

Traveling wave theory

A
  • Bekesy studied it on cadavers
    1. response always begins at the base
    2. amplitude grows as it travels apically
    3. reaches a peak at a point determined by frequency of the sound
    4. vibration then dies out rapidly
  • pressure difference across the basilar membrane
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22
Q

tonotopical organization

A

organization of the cochlea

-processing of sounds of diff freq at different locations along the membrane

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23
Q

perilymph concentrations

A

high concentrations of Na and low concentrations of K

  • very similar to cerebrospinal fluid
  • similar to the inside of the Organ of Corti
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24
Q

endolymph concentrations

A

high concentrations of K and low concentrations of Na

-significantly more positive than perilymph

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25
Q

cochlear fluids

A

the difference or gradient in ion composition and concentration of endolymph versus perilymph serves as an inner ear battery, supplying power for cochlear functions
-electrochemical potential difference in the cochlea is critical for powering the ongoing active processes within the cochlea

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26
Q

organ of corti

A

a complex of structures located on the BM
plays a critical role in hearing
rods and pilots form the main supporting framework and enclose the tunnel of Corti
-superior border= tectorial membrane
-contains cortilymph

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27
Q

inner hair cells

A

shaped like goblet or flask

  • contain nucleus toward the center and mitochondria scattered throughout the cell
  • stereocilia are in a single row and are not imbedded in the tectorial membrane
28
Q

outer hair cells

A

shaped like cylinder or tube
contains nucleus near the base
mitocondria are arranged along the walls
stereo cilia are imbedded in the tectorial membrane
-stereocilia are arranged in 3 or 4 rows

29
Q

movement of stereocilia

A

plays important role in converting mechanical energy from sound vibrations into chemical and electrical energy within hair cells

30
Q

outer hair cell motility

A

vibrations of the BM activates the OHC

  • movement of OHC is enhanced because the tops of tallest stereocilia are imbedded in tectorial membrane
  • when activated the OHC alternatively become longer and skinner and then shorter and fatter
  • rapid up and down movement
  • contributes to movement of the BM and normal hearing
31
Q

prestin

A

specialized motor protein

rapid elongation and shortening is the underlying reason for motility of the OHC

32
Q

otoacoustic emissions

A

what causes the cochlea’s sensitivity and freq tuning at low and moderate intensities

33
Q

recruitment

A

what happens in patients with sensory neural hearing loss

-rapid growth of loudness

34
Q

OHC difference

A

the energy supplied by the OHC motility helps overcome the loss of energy that occurs as the BM moves within the thick cochlear fluids
OHC motility improves our hearing sensitivity by 40-50 dB and contributes to our ability to distinguish freq

35
Q

IHC difference

A

additional energy in the cochlea associated with OHC motility adds to vibration of the BM and increases activation of the IHC
-we cannot hear with our OHC alone, IHC function is essential - sends the info to the brain

36
Q

efferent fibers

A

brain to the cochlea

37
Q

afferent fibers

A

cochlea to the brain

38
Q

VIII consists of….

A

type 1 and type 2 fibers

39
Q

type 1 fibers of VIII

A

large and myelinated
make up 95% of the nerve
innervate the IHCs

40
Q

type 2 fibers of the VIII

A

small myelinated and unmyelinated

innervate with the OHCs

41
Q

afferent neural pathways

A

carry info from the ear to the brain and in a rostal direction through the brain

  • 95% communicate directly with the IHCs
  • only 5% make connections with the OHCs
42
Q

efferent system auditory system

A

descending pathways

  • runs downward from the brain into the ear
  • final portion of this system consists of nerve fibers originating in the lowest region of the brain that travel downward through the internal auditory canal to the cochlea
43
Q

efferent innervation of the OHC

A

inhibitory

-reduces the afferent activity caused by hair cell stimulation

44
Q

crossed olivocochlear bundle

A

innervates the OHCs

45
Q

uncrossed olivocochlear bundle

A

innervates the IHCs

activation is controlled by the cortical activity and assists in detection of a signal within background noise

46
Q

what is hearing dependent on?

A

transmission of electrical activity from the inner hair cells to the auditory nerve
-hair cells communicate with nerve fibers through a synapse which is defined as a “point of contact:

47
Q

auditory neuropathy

A

disruption in the transmission of information from inner hair cells to and along nerve fibers results neural auditory dysfunction

48
Q

eighth cranial nerve

A

transmits auditory and vestibular info from the ear to the brain
-almost all fibers connect via synapse with the IHCs
10-20 afferent fibers synapse with a single hair cell
-enclosed in a narrow passageway in the temporal bone called the internal audiotory canal

49
Q

efferent auditory pathway

A

important for auditory function

-extends downward within the internal auditory canal from the lower region of the brain to cochlear hair cells

50
Q

internal auditory artery

A

blood supply to the cochlea after it branches off larger blood vessels near the brain
-important for auditory function

51
Q

auditory nerves

A

bipolar and consist of a cell body with 2 axons projecting from the cell body in opposite directions

52
Q

spiral ganglion

A

collection of auditory nerve cell bodies

53
Q

Rosenthal’s canal

A

passageway within the temporal bone that fibers travel medially into the modiolus

54
Q

habenulae perforata

A

nerve fibers exit through small openings in the osseous spiral lamina

55
Q

radial fibers

A

type 1 auditory nerve fibers

-innervate the IHCs

56
Q

characteristic frequency

A

activation is the greatest and the auditory nerve fiber is activated with the lowest sound intensity

57
Q

frequency selectivity

A

responsiveness of auditory neurons to sounds at specific frequencies and not for sounds at other frequencies

58
Q

coding of intensity

A

intensity of sound is partially represented as the number of spikes per second for nerve fibers
-firing rate increases only over a range of 20-50 dB of sound intensity

59
Q

structures of the auditory brainstem

A

cochlear nuclei
superior olivary complex
lateral lemniscus
inferior colliculus

60
Q

cerebellopontine angle

A

fibers from the right ear and the left ear enter into the brainstem at the junction of the medulla and the pons on each side of the brainstem

61
Q

peripheral portion

A

outer, middle and inner ear

62
Q

central portion

A

auditory nerve
brainstem
thalamus
auditory cortex

63
Q

auditory afferent nuclei

A 
8th nerve 
cochlear nucleus 
superior olivary complex 
lateral lemniscus 
inferior colliculus 
medial geniculate body 
auditory cortex
64
Q

efferent auditory system

A

begins in the auditory cortex and includes pathways within each of the major auditory centers for the afferent system
-may be related to disorders like tinnitus

65
Q

olivocochlear bundle

A

efferent fibers from the olivary complex in the brainstem that descend to the inner ear

66
Q

medial OCB fibers

A

lead directly to the outer hair cells

67
Q

lateral OCB fibers

A

indirect connections with inner hair cells

CDS 4300 exam 2 (4 decks)

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