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MBBS2/Physiology~HEAD & NECK > The auditory system > Flashcards

The auditory system Flashcards

1
Q

what is sound

A

are audible variations in air pressure

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2
Q

what do we perceive high frequency waves as

A

a high pitch

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3
Q

what do we perceive high intensity waves as

A

louder

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4
Q

what is the range the human auditory system can respond to pressure waves

A

20Hz-20 000Hz

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5
Q

for a sound to be perceived as having a pitch (low and high) its determined by what

A

frequency

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6
Q

what does sound intensity determine

A

the loudness we perceive

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7
Q

the outer ear extends from where to where

A

pinna to the tympanic membrane

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8
Q

what makes sound waves stronger / amplifies sound in the outer ear

A

pinna

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9
Q

what is the design of the human pinna like

A

has a poor design ( when you cup your ears the sound quality improves)

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10
Q

what is the tympanic membrane

A

its a thin semi transparent partition between the outer ear and middle ear

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11
Q

what covers and lines the tympanic membrane

A

its covered by the epidermis and lined by simple cuboidal epithelium

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12
Q

how long do tears on the tympanic membrane take to heal

A

a month

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13
Q

what lines the eternal acoustic meatus

A

hair cells and specialized sweat glands called ceruminous glands

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14
Q

what do ceruminous glands do

A

secrete cerumen/ earwax

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15
Q

what are the functions of ear wax

A

-keeps skin in ear canal soft
-keeps bugs out

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16
Q

what happen to sound waves in the middle ear

A

they change to mechanical energy

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17
Q

what separates the middle ear from the inner ear

A

the round and oval window

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18
Q

what parts make up the middle ear

A

-the back of the tympanic membrane
-3 auditory ossicles (malleus, incus, stapes)
-eustachian tube

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19
Q

what do the ossicles do

A

they transmit vibrations from the tympanic to the oval window

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20
Q

what is the handle of the malleus attached to

A

the inner wall of the tympanic membrane

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21
Q

what is the head of the malleus attached to

A

its attached by a tiny synovial joint to the incus

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22
Q

which part of the stapes is in contact with the oval window

A

the foot plate

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23
Q

what keeps the foot plate of the stapes held in place in the oval window

A

a flexible annular ligament

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24
Q

why cant sound waves simply directly move the membrane at the oval window

A

-because the cochlea is filled with fluid not air
-because the fluid in the inner ear resists being moved much more than air does, so more pressure is needed to vibrate the fluid than the air can provide
-because ossicles provide the necessary amplification in pressure

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25
Q

when will the pressure at the oval window become greater than the pressure at the tympanic membrane

A
  • when the force on the oval window membrane is greater than that on the tympanic membrane
    -when the surface area of the oval window is smaller than the area of the tympanic membrane
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26
Q

how does the middle ear increase pressure at the oval window

A

by altering both the force and surface area

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27
Q

what innervates the tensor tympani muscle

A

the trigeminal nerve

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28
Q

what is the tensor tympani attached and anchored to

A

its attached to the malleus and anchored to bone in the middle ear cavity

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29
Q

what innervates the stapedius muscle

A

the facial nerve

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30
Q

where is the stapedius muscle anchored and attached to

A

its anchored to a bone in the middle ear cavity and attaches to the stapes

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31
Q

what happens when the stapedius and tensor tympani muscle contract

A

the chain of ossicles become much more rigid and sound conduction to the inner ear is greatly diminished

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32
Q

what does an onset of a loud sound trigger

A

a neural response i.e. the attenuation/ acoustic reflex that causes the muscles to contract

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33
Q

when is sound attenuation much greater

A

at low frequencies that at high frequecies

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34
Q

why does the attenuation reflex not offer much protection

A

this is because it has a 50-100msec delay from the time that sound reaches the ear, hence why it doesnt offer much protection from very sudden loud sounds, so damage might already be done by the time the muscles contract

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35
Q

when is the attenuated reflex thought to be activated since the reflex suppresses low frequencies more than high

A

when we speak, so we don’t hear our own voices as loudly as we otherwise would

36
Q

what does the eustachian tube do

A

-drains cells/tissues
-it equalizes air pressure between the outside air and middle ear cavity

37
Q

how is the eustachian tube normally closed or open

A

yawning, chewing and swallowing opens the tube by contracting the tensor palatini muscles

38
Q

how does the eustachian tube play a role on otitis media

A

pathogens travel from the throat and nose via the eustachian tube

39
Q

why are children more susceptible to ear infections (otitis media)

A

because their auditory tubes are shorter, narrow, and almost horizontal which decreases drainage efficiency

40
Q

the first 1/3 of the tube is surrounded by what

A

bone

41
Q

the remainder 2/3 of the eustachian tube is surrounded by what

A

an incomplete ring of elastic cartilage

42
Q

what is the meeting point of the bony and cartilaginous portions of the eustachian tube

A

isthmus

43
Q

why is constant supply from the eustachian tube necessary

A

because cells lining the middle ear absorb air

44
Q

what happens when the eustachian tube is blocked

A

the eardrum is sucked into the middle ear and this causes pai, pressure and hearing loss

45
Q

how can fullness in ears be alleviated

A

by popping the ears (when eustachian tube opens)

46
Q

what normally keeps the eustachian tube in the closed state

A

the hook shaped arrangement of the eustachian tube cartilage

47
Q

what does the inner ear consist of

A

the cochlea and labyrinth

48
Q

the cochlea is part of what system

A

auditory system

49
Q

the labyrinth is a part of what system

A

the vestibular system

50
Q

what is the cochlea

A

its a snail shaped, pea sized and filled with fluid

51
Q

what are the 3 tubes of the cochlea

A
  1. scala vestibuli
  2. scala media
  3. scala tympani
52
Q

what does the scala vestibuli contain

A

perilymph which is similar to CSF and has low K+ and high Na+

53
Q

what does the scala media contain

A

endolymph which has ionic concs similar to intracellular fluid i.e. high K+ and low Na+

54
Q

what does the scala tympani contain

A

perilymph, which is similar to CSF and has low K+ and high Na+

55
Q

what does the scala vestibuli meet

A

oval window

56
Q

what does the scala tympani meet

A

the round window

57
Q

what does inward motion at the oval window do

A

pushes perilymph into the scala vestibuli, and because the fluid pressure has no where to escape the membrane at the round window then bulges out in response to the inward movement of the membrane at the oval window

58
Q

what is the cochlear duct

A

its a small canal in the bony labyrinth that contains the perilymphatic which drains perilymph into the CSF of the subarachnoid space

59
Q

where does the lateral end of the cochlear duct arise from

A

the scala tympani

60
Q

where is the endolymphatic sac and duct

A

the membranous labyrinth

61
Q

what does the endolymphatic duct do

A

drain endolymph from the auditory and vestibular apparatus

62
Q

what does the endolymphatic sac do

A

it acts as both a reservoir for endolymph and the site for reabsorption into the epidural space

63
Q

on the surface of the basilar membrane of the cochlea lies what

A

the organ of corti

64
Q

what does the organ of corti contain

A

hair cells

65
Q

where are the hair cells in the cochlea

A

they are sandwiched between the basilar membrane and the reticular lamina

66
Q

what do the rods of corti (pillar cells) do

A

they span the basilar membrane and tectorial membrane and provide structural support

67
Q

in the organ of corti hair cells between the modiolus and the rods of corti are called what

A

inner hair cells (arranged in a single row)

68
Q

in the organ of corti cells farther out than the rods of corti are called what

A

outer hair cells (arranged in 3 rows)

69
Q

each hair cell in the organ of corti has what

A

about 100 stereocilia on its apical border

70
Q

the hair cells in the organ of corti extend how

A

they extend above the reticular lamina into the endolymph

71
Q

where do the tips of the hair cells in the organ of corti end

A

in the gelatinous substance of the tectorial membrane (outer hair cells) or below the tectorial membrane (inner hair cells)

72
Q

what do the hair cells in the organ of corti do

A

generate impulses in response to sound vibrations

73
Q

where do stereocilia become progressively longer

A

on the side of the hair cell away from the modiolus

74
Q

what are the tops of the shorter stereocilia are attached to what

A

to the back sides of the longer adjacent longer stereocilia by thin filaments

75
Q

what happens when the cilia are bent in the direction of the longer stereocilia (auditory signal transduction)

A

-the tips of the smaller stereocilia are tugged outward from the surface of the hair cells
-this causes a mechanical transduction, where cation conducting channels open and there is a K+ influx from the surrounding scala media fluid into the stereocilia and the hair cell membrane gets depolarized
-this then opens voltage gated calcium channels
-Ca2+ influx then triggers the release of the neurotransmitter glutamate which activates the spiral ganglion fibres lying postsynaptic to the hair cell

76
Q

what are the central pathways for the auditory system

A

-afferents from the spiral ganglion enter the brain stem in the auditory vestibular nerve
-at the level of the medulla the axons innervate the dorsal cochlear nucleus and the ventral cochlear nucleus ipsilateral to the cochlea where the axons originated
-from the cochlear nucleus auditory info is transmitted to:
1. superior olivary nucleus (pons, decussation)
2. lateral lemniscus (midbrain)
3. inferior colliculus (midbrain)
4. medial geniculate nuclei (thalamus)

77
Q

all levels of the central auditory system receive and process info from where

A

both the ipsilateral and contralateral sides

78
Q

what is otitis externa

A

inflammation of the outer ear

79
Q

what is otitis media

A

inflammation of the middle ear

80
Q

what is cholesteatoma

A

its a skin lined cyst that begins at the margin of the eardrum and invades the middle ear and mastoid (benign tumor)

81
Q

what is conductive hearing loss

A

its damage to or obstruction of the outer or middle ear

82
Q

what is sensorineural hearing loss

A

its gradual loss of hearing resulting from an abnormality in either the inner ear, auditory nerve or both

83
Q

what is tinnitus

A

ringing in the ear

84
Q

what causes tinnitus

A

-exposure to loud noises
-aging
-infections

85
Q

what things can block the auditory tube

A

-inflammation of the nasal lining, which narrows the opening
- nasal allergy
-obesity (excess fat deposits along passageway)

86
Q

What other things can block the eustachian tube

A

-inflammation of the nasal lining
-nasal allergy
-obesity

MBBS2/Physiology~HEAD & NECK (3 decks)

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