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ANAT + PHYS (9610) > UNIT 7: Inner Ear > Flashcards

UNIT 7: Inner Ear Flashcards

1
Q

the inner ear is comprised of

A

the organs of hearing and equilibrium

structurally linked

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2
Q

organs of hearing and equilibrium are innervated by

A

vestibulocochlear nerv CN VIII

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3
Q

systems of hearing and equilibrium consist of

A

osseous labyrinth and membranous labyrinth

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4
Q

osseous labyrinth includes

A

semicircular canals, vestibule, cochlea

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5
Q

membranous labyrinth consists of

A

semicircular ducts, utricle, saccule, cochlear duct

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6
Q

the human balance sys is comprised of

A

vestibular sys
vision
proprioception

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7
Q

CN VIII - vestibulocochlear has 2 components

A

vestibular and auditory

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8
Q

describe the osseous labyrinth… fluid?… how many parts?

A

series of continuous spaces surrounded by bone

spaces are fluid filled - fluid is perilymph

has 3 parts

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9
Q

3 parts of osseous labyrinth

A

semicircular canals (vestibular sys)
vestibule (vestibular sys)
cochlea (auditory sys)

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10
Q

semicircular canals are 3 canals that for the …. names of the canals are…. each SCC is approx …

A

posterior portion of the osseous labyrinth

anterior, posterior, and lateral

2/3 of a complete circle

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11
Q

each SCC has a dilated portion called an _____, SCCs enclose the ________ of the _______ labyrinth

A

ampulla

semicircular ducts

membranous labyrinth

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12
Q

Vestibule is the

A

middle dilated portion of the osseous labyrinth

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13
Q

______ and _____ of the middle ear are located on the vestibule

A

fenestra vestibuli
fenestra cochleae

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14
Q

vestibular aqueduct passes…

A

passes posterioinferiorly from the vestibule and opens on the posterior surface of the pertous bone

transmits endoymphatic duct and sac

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15
Q

what does the vestibule house

A

the utricle and saccule of the membranous labyrinth

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16
Q

cochlea is a ____ tube w approx ____ turns, its wide basal turn forms the _____

A

helical
2 3/4 turns
promontory

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17
Q

the cochlea lies on its side in the ____, with its apex pointing _____

A

petrous bone
anterolaterally

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18
Q

the cochlea encloses the

A

cochlear duct of the membranous labyrinth

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19
Q

cochlea has a bony core called the _____, what passes thru this structure?

A

modiolus

cochlear portion of CN VIII and spiral ganglia pass thru it

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20
Q

shelves of bone project laterally from the modiolus called the

A

osseous spiral laminae

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21
Q

spiral laminae partially divide the cavity of the cochlea into 2 portions…

A

scala vestibuli anteriorly and scala tympani posteriorly

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22
Q

at the apex of the cochlea, scala vestibulu and scala tympani communicate via a small opening called

A

helicotrema

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23
Q

division of the cochlea is completed by the

A

cochlear duct (scala media) of the membranous labyrinth

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24
Q

scala vestibuli begins at

A

fenestra vestibuli (oval window), which is occupied by the footplate of the stapes

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25
Q

scala tympani ends at

A

the fenestra cochleae (round window), which is closed by a secondary tympanic membrane

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26
Q

both scala vestibuli and tympani are filled w

A

perilymph

aka osseous labyrinth

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27
Q

perilymph is

A

an extracellular fluid, similar in composition to plasma or cerebrospinal fluid

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28
Q

the membranous labyrinth is…

A

a series of connected ducts and sacs housed w/i and protected by the osseous labyrinth

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29
Q

membranous labyrinth is comprised of

A

semicircular ducts
utricle
saccule
cochlear duct/scala media

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30
Q

ducts and sacs in the membranous labyrinth are filled w

A

endolymph

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31
Q

describe endolymph

A

more viscous than perilymph, similar composition to intracellular fluid

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32
Q

endolymph is produced by

A

stria vascularis in the cochlear duct

moved toward the venous sys at the base of the brain by the endolymphatic duct

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33
Q

semicircular ducts are approx ___ of the diameter of the SC canals

A

1/4

34
Q

each SCD has an _____ end, which contains …

A

ampullated end

contains a patch of sensory epithelium - the ampullary crest or crista ampullaris

35
Q

crista ampullaris is

A

w/i the SCDs

a patch of sensory epithelium

sensory receptors for detecting rotational movement of the head

contains hair cells

36
Q

the hair cells of crista ampullaris have basal parts which synpase w

A

the vestibular nerve of CN VIII

37
Q

crista ampullaris hair cells have stereocilia which project into a

A

tall, jelly-like mass called the cupula

38
Q

@crista ampullaris: as the head rotates, endolymph moves opposite to the direction of rotation and…

A

pushes on the cupula bending the stereocillia

39
Q

utricle communicates w

A

semicircular ducts

40
Q

saccule communicates w the…. via the…

A

cochlear duct

via the utriculosaccular duct

41
Q

both the utricle and saccule contain..

A

a patch of sensory epithelium called the macula

42
Q

utricle and saccule monitor the position of the…. and straight-line changes in …

A

head, aka static equilibirum (lying down, sitting up etc)

in speed and direction of head movements, aka linear acceleration (ex. walking, going up an elevator)

43
Q

maculae is a

A

patch of epithelium w columnar supporting cells and scattered hair cells

44
Q

hair cells in the maculae synapse w

A

fibres of the vestibular nerve of CN VIII

45
Q

maculae: each hair cells has …. and the tips of the stereocilia are …

A

many stereocilia protruding from its apex

tips are embedded in overlying otolithic membrane

46
Q

otolithic membrane of the maculae is…

A

a jelly like disc containing heavy crystals of calcium carbonate called otoliths

47
Q

macula of the utricle is for ___ orientation, which indicates…

A

horizontal

indicates head tilting and linear movement - forward, backward, sideways movement in a straight line

48
Q

macula of the saccule is for ___ orientation, which indicates…

A

vertical orientation

indicates head’s upright position and linear movement - forward, backward, upward, downward movement

49
Q

how is the otolithic membrane like a sac of marbles

A

So it will go in the opposite direction only when you are walking forward, back … think of dragging a sac of marbles behind you, hair cells will be bent behind you in opp direction

But if you are tilting head down gravity will pull sac of marbles down, and the hair cells will bend down in the same direction

50
Q

describe the cochlear duct/scala media

A

spiral tube housed in cochlea (25-35 mm)

occupies the lateral portion - completes the division of the cochlea, started by the spiral laminae, into scala vestibuli and scala tympani

51
Q

what 3 things form the “triangle” of the cochlear duct

A

basilar membrane
vestibular membrane
spiral ligament

52
Q

basilar membrane is

A

floor of cochlear duct/scala media

supprots the organ of hearing = organ of corti

53
Q

vestibular membrane is

A

roof of the cochlear duct

joins the basilar mem at the helicotrema

54
Q

spiral ligament is

A

forms the lateral wall of the cochlear duct

stria vascularis on surface of spiral ligament

55
Q

organ of corti is…

A

a cellular structure along the length of the cochlear duct

many cells serve a supportive function

56
Q

hair cells of the organ of corti have stereocillia that project from….which are embedded in….

A

apex of hair cells

the overhanging jelly-like tectorial membrane

57
Q

hair cells of the organ of corti are innervated by

A

cochlear nerve of CN VII

58
Q

movement of the fluid in the cochlear duct leads to

A

movement of the basilar membrane, bending the stereocillia and generating a nerve impulse

59
Q

how many rows of inner hair cells on the organ of corti?

A

1

60
Q

approx _____ IHCs on the medial side of the tunnel of corti

A

3500

61
Q

how many stereocilia on each IHC? how are they arranged?

A

40 - arranged in parallel rows, dec in height towards the modiolus

62
Q

how many rows of outer hair cells on organ of corti?

A

3 to 5

63
Q

how many outer hair cells?

A

1200

64
Q

how many stereocilia on OHCs? how are they arranged?

A

150 stereocilia per OHC

arranged in the form of a V or W (base of letter points toward spiral lig) w dec height toward the modiolus

65
Q

describe size/shape of OHCs

A

long and thin (cylindrical)

tallest tips of OHC stereocilia are embedded in the tectorial membrane

66
Q

describe size/shape IHCs

A

fat and round

tips of IHC stereocilia are not embedded in the tectorial membrane

67
Q

if the IHCs are not embedded in the tectorial membrane how do they move?

A

Outer hair cells are tall and thin, embedded in tectorial membrane, when the basilar membrane moves, the outer hair cells embedded move the tectorial membrane and this creates turbulence in the endolymp which makes the inner hair cells move

We need the outer hair cells to help the inner hair cells fire

68
Q

afferent fibres send sound information in the cochlea to the …… and have cells bodies in the ….

A

CNS
spiral ganglion

69
Q

______ make up 95% of the nerve fibres in the cochlear nerve

A

Type I myelinated

many type I fibres innervate a single IHC

70
Q

____ make up 5% of nerve fibres in the cochlear nerve

A

type II unmyelinated

one type II fibre innervates many OHCs

71
Q

what are the 3 functions of the cochlea

A

transforms sound vibrations into neural impulses

separates sounds according to their freq

compresses amplitude of sounds

72
Q

IHCs have most responsibility of….

A

hearing, that is sending afferent info regarding sound to CNS (function #1)

73
Q

IHCs selectively respond to…

A

frequency (function #2)

74
Q

OHCs are thought of as ….

A

amplifiers - they have the ability to change cell shape by receiving efferent fibres from the descending auditory nervous sys (function #3)

75
Q

OHCs compensate for loss of energy w/i the ….

A

cochlea, improving the ear’s sensitivity and sharpening ist freq selectivity for weak sounds

76
Q

OHCs inc the movement of …

A

the basilar membrane to amplify the activity of the IHCs

77
Q

structure of the basilar membrane influences

A

its resonant properties and freq response characteristics - like a diving board

narrow and stiff at base and wide and floppy at apex

low freq sound cause vibration at the apex of the cochlea

78
Q

what are the steps of hearing

A

Sound waves enter the ear through EAM

TM vibrates from sound waves, sending vibrations to ossicles

Ossicles amplify the sound vibrations and send them through the oval window to the cochlea of the inner ear

The vibrations cause the fluid inside the cochlea to ripple, a travelling wave forms along the basilar membrane – the hair cells sitting on top of the basilar membrane ride the way

As the hair cells move up and down the stereocilia on top of the hair cells bump against the tectorial membrane, causing them to bend

When the stereocilia bend it opens channels that are at the tips of the stereocilia, chemicals rush into the cells creating an electrical signal

Auditory nerve carries electrical signal to the brain

79
Q

meniere’s disease

A

too much endolymph

leads to both hearing and vestibular disturbance (tinnnitis, fluctuating HL, rotatory vertigo)

hearing returns to normal after attacks early in the disease process, as the disease progresses, residual hearing loss accumulates, and hearing loss spreads from low freq to high freq

80
Q

benign paroxysmal positional vertigo (BPPV)

A

otolithic memebrane falls off utricle due to injury, age, drug effects - migrates toward semicircular ducts

come to rest in a SCD (usually posterior) and creates a sensation of vertigo

symptoms worsen if they rest on the cupula

debilitating; always precipitated by a change in head position like rolling over in bed

ANAT + PHYS (9610) (21 decks)

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