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Neurophysiology Loyola > Auditory System > Flashcards

Auditory System Flashcards

1
Q

What is the function of the outer ear

A

Collection of sound; protection, funneling of sound, and spectral filtering for sound localization

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2
Q

What is the function of the inner ear

A

Transduction of sound; functions as the sensory transducer of sound-driven vibrations, gravity, and acceleration into neuronal signals via inner hair cells

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3
Q

What is the function of the middle ear

A

Conduction/Amplification of sound; serves as an impedance matching device, allowing for adequate transfer of energy from air-borne sound to fluid-filled cochlea

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4
Q

What is the route of conduction of sound from the middle to the inner ear?

A

Tympanum –> malleus –> incus –> stapes –> oval window –> scala vestibuli –> helicotrema –> scala tympani –> round window

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5
Q

What is the stapedius reflex?

A

Contraction of the stapedius in response to high intensity sounds or just before speaking

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6
Q

What is the route of the stapedius reflex?

A

Loud sound travels to auditory nerve –> V. Cochlear nucleus –> S. Olivary nucleus –> facial motor nucleus, which release ACh to cause stapedius muscle contraction

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7
Q

How does sound transduction occur?

A

Pressure oscillations in the cochlea induce movement (vibration of the organ of corti); different parts of the basilar membrane move optimally at different frequencies of sound

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8
Q

What is endolymph

A

Contains high K+ and low Na+ and protein. +80mV, secreted from stria vascularis via Na/K

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9
Q

What is perilymph

A

Similar to interstitial fluid, with high Na+ and Cl-, low protein

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10
Q

What is the difference between perilymph and endolymph

A

Perilymph has high Na+, endolymph has low Na+; both have low protein; perilymph fills the vestibuli and tympani while endolymph fills the cochlear duct (media)

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11
Q

What is the result of the Rinne test if there is unilateral conduction hearing loss?

A

Bone louder than airborne

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12
Q

What is the result of the Weber test if there is unilateral conduction hearing loss?

A

Louder on affected side

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13
Q

Where does sound travel faster, water or air?

A

WATER, but most of it gets rejected

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14
Q

Which bone of the middle ear is referred to as the “anvil”

A

incus

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15
Q

Which bone of the middle ear is referred to as the “stirrup”

A

stapes

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16
Q

Which bone of the middle ear is referred to as the “hammer”

A

Malleus

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17
Q

What is the innervation of the middle ear?

A

A branch of the facial nerve and a branch of the trigeminal nerve

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18
Q

What is the musculature of the middle ear

A

Stapedius muscle and tensor tympani muscle

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19
Q

What do the facial nerve branch and stapedius muscle act on?

A

The stapes; nerve innervates the stapedius muscle

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20
Q

What do the trigeminal nerve branch and tensor tympani muscle act on?

A

tympanic membrane (muscle travels through the proximal portion of the eustachian tube); nerve innervates the tensor tympani

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21
Q

How does contraction of the middle ear muscles (stapedius and tensor tympani) affect amplification

A

Decreases amplification of the movements of the middle ear ossicles (increased impedance)

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22
Q

What is the purpose of contraction of the middle ear muscles

A

Protection against loud sounds, especially at lower frequencies to allow detection of higher frequencies

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23
Q

Where does the perilymph drain?

A

From the perilymph duct into the CSF of the subarachnoid space

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24
Q

What is the helicotrema

A

Apex of the cochlear labyrinth. The hair cells near this area best detect low frequency sounds.

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25
Q

What are the 3 fluid filled chambers of the cochlea?

A

Scala vestibuli, scala tympani, and scala media (cochlear duct)

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26
Q

What is the organ of corti

A

Site of mechano-electrical transduction

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27
Q

What is the frequency discrimination in humans?

A

0.2%

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28
Q

What three factors does frequency discrimination depend upon?

A
  1. tonotopic organization of hair cells
  2. membrane potential
  3. cilia length
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29
Q

What is place theory?

A

The PLACE along the basilar membrane where the optimal hair cell discharge is attained; explains how frequencies of sound are coded

30
Q

What causes the bending of cilia?

A

Basilar membrane moving up and down, resulting in the organ of corti sliding in and out relative to the tectorial membrane

31
Q

Does the basilar membrane go up or down during excitation? inhibition?

A

Excitation - up

inhibition - down

32
Q

How does inner hair cell transduction work?

A

K+ and Ca++ influx results in glutamate release, which acts on AMPA-type glutamate receptors of cochlear nerve fibers

33
Q

What is the auditory pathway, starting from the dorsal acoustic stria

A

Cochlear nuclei –> dorsal acoustic stria –> contralateral to the nucleus of lateral lemniscus (pons) –> inferior colliculus (midbrain) –> medial geniculate nucleus (midbrain) –> primary auditory cortex (AKA temporal gyrus, Heschl’s gyrus, area 41)

34
Q

What is the auditory pathway, starting from the trapezoid body

A

Cochlear nuclei –> trapezoid body –> bilateral superior olivary nuclei (pons) –> bilateral nuclei of lateral lemniscus –> bilateral inferior colliculus –> unilaterally to medial geniculate nucleus –> primary auditory cortex

35
Q

What is the auditory pathway, starting from the intermediate acoustic stria

A

Cochlear nuclei –> intermediate acoustic stria –> nucleus of the lateral lemniscus –> inferior colliculus –> medial geniculate nucleus –> primary auditory cortex

36
Q

What are the 5 main classifications of deafness?

A

Conduction, sensorineural, neural, central, genetic

37
Q

What is the sound intensity level equation?

A

L = 20log(P/Pref)

38
Q

What is the decibel loss equation?

A

-20log(Ppt/Pnl)

39
Q 
A noise level of 20 decibels would best equate to which of the following?
A) a quiet room at night
B) A busy street
C) a pneumatic drill
D) Aircraft taking off
A

A) Quiet room

40
Q

A noise level of 60 decibels would best equate to which of the following?

A) Personal music player at high volume
B) A busy street
C) An ordinary spoken conversation
D) Aircraft taking off

A

C) an ordinary spoken conversation

41
Q 
A noise level of 70 decibels would best equate to which of the following?
A) a quiet room at night
B) A busy street
C) a pneumatic drill
D) Aircraft taking off
A

B) a busy street

42
Q 
A noise level of 100 decibels would best equate to which of the following?
A) a quiet room at night
B) A busy street
C) a pneumatic drill
D) Aircraft taking off
A

C) a pneumatic drill

43
Q 
A noise level of 105 decibels would best equate to which of the following?
A)  Personal music player at high volume
B) A busy street
C)  An ordinary spoken conversation
D) Aircraft taking off
A

A) Personal music player at high volume

44
Q 
A noise level of 110 decibels would best equate to which of the following?
A)  Personal music player at high volume
B) A busy street
C)  An ordinary spoken conversation
D) Aircraft taking off
A

D) Aircraft taking off

45
Q

What is BAER used for?

A

Brain stem auditory evoked response is used to assess auditory function in infants and in general in patients not able to respond

46
Q

What are the steps in audiometry?

A
  1. present different tones to each ear
  2. increase intensity to threshold
  3. Hearing ability at given frequency is given as threshold pressure compared to normal population and is presented as hearing loss in decibels
47
Q

What is the amount of decibel loss that is considered abnormal?

A

> -20 dB loss

48
Q

What would be the decibel loss if a patient’s threshold pressure is 1000x normal?

A

60

49
Q

What is conduction deafness?

A

Decreased vibrations to the basilar membrane and decreased air conduction; bone conduction is okay

50
Q

Which frequency range is affected in conduction deafness?

A

Broad range, but especially low frequencies

51
Q

Which frequency range is affected in conduction deafness?

A

Broad range, but especially low frequencies

52
Q

What are possible causes of conduction deafness?

A

Foreign objects/wax in the ear canal, otitis media, otosclerosis

53
Q

What is otosclerosis?

A

A cause of conduction deafness; overgrowth of temporal bone around oval window, limiting stapes movement

54
Q

What are the treatments for conduction deafness?

A

Remove cause, surgery, hearing aids

55
Q

What are the presynaptic changes during temporary conduction hearing loss?

A

Decrease in VGlut1 in auditory nerve endings and SV size

56
Q

What are the postsynaptic changes during temporary conduction hearing loss

A

Thicker PSD, increased GluA3 AMPARs - decrease in vesicular glutamate transporter postsynaptic densities altered as well

57
Q

What are presynaptic changes when hearing is restored after temporary conduction hearing loss

A

Increased SV size and density in auditory nerve endings

58
Q

What are the postsynaptic changes when hearing is restored after temporary conduction hearing loss

A

Thicker and larger PSD, increased GluA3, fewer GluA2 AMPARs

59
Q

What is sensorineural deafness

A

Loss of both air and bone conduction

60
Q

What frequencies are affected in sensorineural deafness

A

High frequencies

61
Q

What are some causes of sensorineural deafness?

A

Chronic loud sounds, aminoglycoside antibiotics (parental use of streptomycin, neomycin, gentamicin, esp. long duration use), quinine, prolonged high doses of aspirin, vaccines (rubella), old age (presbyacusis)

62
Q

What is the treatment for sensorineural deafness?

A

Hearing aids (microphone-amplifier-speaker)

63
Q

Hair cell loss can be associated with which classification of deafness?

A

Sensorineural

64
Q

What is the purpose of cochlear implants?

A

They are important for severe and complete hearing loss; they are multi-channel stimulatory devices placed in the cochlear duct

65
Q

What is neural deafness?

A

Unilateral, sensorineural deafness

66
Q

What are the most common causes of neural deafness?

A

Schwannoma or acoustic neuroma of auditory nerve in the internal auditory canal

67
Q

What is central deafness

A

Deafness that may manifest as auditory hallucinations (schizophrenia, temporal lobe damage, seizures), pure word deafness, auditory agnosia, and amusia (right hemisphere)

68
Q

What are possible causes of central deafness?

A

Lesion in the CNS causing abnormal processing of auditory signals (very rare) OR bilateral brainstem injury (inferior colliculus) OR cortical deafness (bilateral embolic stroke Heschl’s gyri)

69
Q

What is the prevalence of genetic deafness?

A

1/1,000

70
Q

Which genes are affected in genetic deafness?

A

Connexins 26 and 30, SLC26A4, and mitochondrial genes

Neurophysiology Loyola (7 decks)

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