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NYCC Neuro 2 > Hearing > Flashcards

Hearing Flashcards

1
Q

how are sound waves produced?

A

periodic variation in air pressure

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2
Q

what is the speed of sound?

A

343m/s
767mi/h

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3
Q

how is sound characterized?

A

by its frequency and intensity

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4
Q

what determines pitch?

A

frequency

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5
Q

how is frequency measured?

A

cycles per second or Hertz (Hz)

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6
Q

what is the audible range of frequencies for humans?

A

20Hz - 20k Hz

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7
Q

what is the frequency of ultrasound and what can it be heard by?

A

> 20k Hz
dogs, cats, mice, dolphins, etc

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8
Q

what is the frequency of infrasound and what can it be heard by?

A

<20Hz
elephants, whales

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9
Q

what are low frequency sounds implicated in?

A

car sickness

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10
Q

what determines loudness?

A

intensity

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11
Q

how is intensity measured?

A

decibels (dB)

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12
Q

what is the loudest tolerable sound?

A

120dB

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13
Q

what are the 3 functional divisions of the ear?

A
  1. external ear
  2. middle ear
  3. inner ear
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14
Q

what is the external ear composed of?

A
  1. pinna (auricle or tragus)
  2. external acoustic meatus (auditory canal)
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15
Q

what is the pinna?

A

cartilaginous sound capturing convoluted funnel of the external ear

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16
Q

what is the external acoustic meatus?

A

2.5cm long tunnel of the external ear that ends at the eardrum

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17
Q

the middle ear is an ____ chamber composed of…

A

air-filled
1. tympanic membrane
2. ossicles
3. tensor tympani & stapedius mm

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18
Q

what is the tympanic membrane?

A

9mm diameter conical membrane of the middle ear

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19
Q

name the 3 ossicles

A

malleus
incus
stapes

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20
Q

the inner ear (labyrinth) is a ____ filled membrane composed of…

A

fluid-filled
1. cochlea
2. vestibule
3. semicircular canals

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21
Q

what is the cochlea?

A

(auditory system)
tube of the inner ear that is spiraling 2.5x around the conical bony modiolus

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22
Q

sound waves cause displacement of the ____ membrane which is transmitted to the ____

A

tympanic
ossicles

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23
Q

the convex portion of the tympanic membrane extends into the cavity of the ____ ear and is attached to the ____

A

middle
malleus

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24
Q

how are the malleus, incus and stapes held together?

A

tiny synovial joints

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25
Q

how is tympanic membrane displacement transferred to the inner ear?

A

stape’s footplate pistons in & out onto the oval window

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26
Q

the middle ear cavity connects to the nasopharynx via the ____, and to the mastoid air space (antrum) via the ____

A

Eustachian tube (auditory tube)
aditus

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27
Q

tensor tympani is innervated by ____ and attaches to the ____, while the stapedius is innervated by ____ and attaches to ____

A

V - malleus
VII stapes

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28
Q

function of tensor tympani & stapedius mm

A

attenuation reflex:
make ossicles more rigid in order to dampen very loud sounds (decreases by 10dB)

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29
Q

why doesn’t the attenuation reflex protect from sudden loud sounds?

A

has a 50-150ms delay

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30
Q

what is the function of the middle ear?

A

enhance pressure so that signal is not lost in translation from air (external & middle ear) to fluid (inner ear)

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31
Q

if the middle ear did not function, what would happen to the energy from sound?

A

only 2% of energy would be transferred from external to inner ear as compared to 67% that normally does

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32
Q

how does the middle ear amplify pressure?

A
  1. surface area of oval window is 17x smaller than tympanic membrane
  2. ossicles act as levers to increase force output on oval window
33
Q

what are the 2 membrane covered holes at the base of the cochlea?

A

oval window
round window

34
Q

what happens when the oval window is displaced by stapes?

A
  • causes fluid movement, most of which is absorbed by fluid in cochlea
  • any “unabsorbed” energy distorts the round window
35
Q

what are the 3 fluid filled chambers of the cochlea?

A
  1. scala vestibuli
  2. scala media
  3. scala tympani
36
Q

what are the 2 membranes between the fluid filled chambers of the cochlea and where are they located?

A

scala vestibuli
- Reissner’s membrane
scala media
- basilar membrane
scala tympani

37
Q

scalas vestibuli and tympani contain ____ and connect at the…

A

perilymph (Na rich)
helicotrema at apex of cochlea

38
Q

scala media (cochlear duct) contains ____

A

endolymph (K rich)

39
Q

how does stria vascularis distribute ions in the endolymph?

A

secreting K while absorbing Na against their concentration gradients
(endolymph has ^K)

40
Q

the Organ of Corti is located on the ____, and is covered by the ____

A

basilar membrane
tectorial membrane

41
Q

what is the Organ of Corti?

A

auditory sensory receptor

42
Q

describe the structure of the basilar membrane

A

base = narrow + rigid
apex = wide + floppy

43
Q

the base of the basilar membrane codes ____ frequency sounds, while the apex codes ____ frequency sounds

A

high
low
(tonotopic map)

44
Q

the Organ of Corti is composed of…

A
  • inner & outer hair cells
  • rods of Corti (pillar cells)
  • supporting cells
45
Q

what ultimately produces a receptor potential on a hair cell?

A

bending of stereocilia on hair cell (converts mechanical energy to receptor potential)

46
Q

describe the location & stereocilia of inner hair cells

A
  • arranged in a row between pillar cells & bony modiolus
  • stereocilia extend in endolymph inferior to tectorial membrane
47
Q

describe the location & stereocilia of outer hair cells

A
  • arranged in 3-4 rows distal to pillar cells
  • stereocilia extend in endolymph ending in tectorial membrane
48
Q

hair cells synapse with dendrites of ____ located in the _____

A

bipolar spiral ganglion cells
modiolus

49
Q

what causes the bending of stereocilia ?

A

when basilar membrane is affected by scalas’ fluid movement, all other structures in Organ of Corti move up or down, causing stereocilia to bend sideways

50
Q

upward movement of the basilar membrane causes…

A
  • stereocilia bend so that K channels on tips open and depolarize hair cells
  • causes Ca channels to open
  • release of NT
  • synapse between hair cells & dendrites of spiral ganglion cells
51
Q

downward movement of the basilar membrane causes ____

A

hyperpolarization

52
Q

most spiral ganglion cells receive synapses from ____

A

inner hair cells

53
Q

why are outer hair cells implicated with sound amplification in the inner ear?

A

ototoxic antibiotics selectively destroy them

54
Q

axons of the spiral ganglion cells form the ____ n

A

cochlear

55
Q

the cochlear nerve follows the ____ organization of the basilar membrane so that…

A

tonotopic
each fiber is most responsive at a specific frequency

56
Q

the cochlear nerve travels to the ____ to synapse with the ____

A

medulla
cochlear nuclei

57
Q

how many ventral and dorsal cochlear nuclei are there?

A

2 ventral
1 dorsal

58
Q

name and describe the cell types of the ventral cochlear nuclei

A
  • stellate cells: encode variety of frequencies
  • bushy cells: fire at onset of sound & aid in localization of sound in horizontal axis
59
Q

name and describe the cell types of the dorsal cochlear nucleus

A
  • fusiform cells: excited or inhibited by wide variety of frequencies & aid in sound localization in vertical axis
  • tuberculoventral cells: respond with a delay & inhibit echo interference
60
Q

cochlear nuclei synapse bilaterally with the ____

A

superior olivary nuclei

61
Q

where do fibers of the cochlear nuclei cross?

A

trapezoid body

62
Q

function of medial superior olivary nucleus

A

sound localization in horizontal axis by processing info about auditory time delay between the 2 ears

63
Q

when is interaural time delay most striking?

A

low frequencies

64
Q

function of lateral superior olivary nucleus

A

sound localization by processing intensity difference between the 2 ears

65
Q

when are intensity interaural differences most striking?

A

high frequencies

66
Q

what forms the lateral lemniscus?

A

fibers from the superior olivary nucleus

67
Q

some fibers from the lateral lemniscus will synapse with the ____, but most synapse with the ____

A

nucleus of the lateral lemniscus
inferior colliculus

68
Q

describe the nuclei of the inferior colliculus and their functions

A
  • 4 layered dorsal nucleus: gathers auditory & somatosensory info
  • multilayered central nucleus has a complete tonotopic map
69
Q

the medial geniculate nucleus receives input from the ____ via the ____

A

inferior colliculus
inferior brachium

70
Q

the medial geniculate nucleus holds a complete ____ map

A

somatotopic

71
Q

fibers from the medial geniculate nucleus form the ____ and end in the ____

A

auditory radiation
primary auditory cortex

72
Q

transverse temporal gyri of heschl constitute areas ____ and ____ of Brodmann and are located…

A

41 & 42
near superior temporal gyrus

73
Q

transverse temporal gyri are ____ organized

A

tonotopically

74
Q

function of transverse temporal gyri of heschl

A

2nd point of sound localization: columns that are responsive to every audible frequency and interaural relationship

75
Q

conductive hearing loss results from…

A

insult to middle ear
- otitis media (middle ear infection): may cause scar tissue that hinders movement of tympanic membrane or ossicles
- otosclerosis (no known cause): ossification between ossicles

76
Q

sensorineural hearing loss results from…

A

loss of cochlear hair cells

77
Q

Weber’s Test

A
  • place tuning fork on vertex or nasion (midline of skull)
  • sound lateralizes to the ear with conductive deafness or away from the ear with sensorineural deafness
78
Q

Rinne’s Test

A
  • place tuning fork on mastoid process
  • when pt can no longer hear it, place tuning fork near ear and patient should be able to hear it
  • if not = conductive hearing loss

NYCC Neuro 2 (28 decks)

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