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SLHS 302 > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

Outer ear primary role

A

to create cues for sound localization (binaural cues)
to amplify sound pressure (free field to tympanic membrane)

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2
Q

Outer ear structures

A

pinna
external auditory canal
tympanic membrane (ear drum)
- connects the outer and middle ear

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3
Q

Pinna

A

protects the outer ear
gives small boost to sound that falls in resonant frequency range
helps with sound localization (especially high frequency)

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4
Q

external auditory canal

A

provides boost to sound in the range of resonant frequency
uses cerumen (ear wax) to protect the middle ear from bacteria, debris and provides lubrication
~2.5cm long

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5
Q

Tympanic membrane (ear drum)

A

Cone shaped structure that completely closes off one end of the ear canal

cone shape funnels the acoustic energy of the sound to its center

Connects to the bones of the middle ear

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6
Q

2 primary acoustic cues from horizontal sound localization

A

Interaural level difference (ILD)
Interaural time differences (ITD)

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7
Q

Interaural level difference (ILD)

A

Larger at high frequencies

Lateral Superior Olive (LSO) in the SOC biased to high frequency (ILDs)

Higher level at left ear

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8
Q

Interaural time differences (ITD)

A

Larger at low frequencies

Medial Superior Olive (MSO) in the SOC biased to low frequency

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9
Q

Middle ear ossicles

A

Malleus, incus, stapes

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10
Q

Middle ear primary role

A

Provide an effective and efficient means to deliver sound to the inner ear

Overcome impedance mismatch
- Air filled middle ear → fluid filled inner ear

middle ear is where neural process of hearing begins

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11
Q

Impedance

A

resistance to movement

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12
Q

High acoustic impedance

A

hard to move (fluid filled tube)
Small movement for given input

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13
Q

Low acoustic impedance

A

easy to move (air filled tube)
Large movement for small pressure input

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14
Q

3 ways to get energy from the ear drum to the inner ear

A

Bone conduction
- The sound could travel via direct vibration of the bones of the skull, bypassing the middle ear and going directly to the inner ear

Air pressure changes in middle ear cavity
- Sound wave would travel through the middle ear without encountering the ossciles and stimulate the oval and round windows directly

Vibration through ossicular chain (main mode for hearing)
- Sound converted into mechanical vibration of the malleus, incus and stapes

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15
Q

What impedance does air-filled ear canal have?

A

low impedance

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16
Q

What impedance does fluid filled cochlea have?

A

high impedance

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17
Q

Eustachian tube

A

Connects middle ear space with nasopharynx (back of nose/mouth)
Opens occasionally, equalizes inside and outside pressure

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18
Q

Stapedius muscle/reflex

A

Stapedius muscle attached to stapes

Controlled by a reflex loop through brainstem, reduces sound transmissions at high sound levels

Stapedius muscle pulls stapes at a right angle to its typical motion, restricting motion by
- Increasing effective stiffness of ossicular chain
- Increases low-frequency impedance
- Reduces low-frequency energy transmission

Provides limited protection from loud sounds

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19
Q

Middle Ear Pathologies

A

Otosclerosis

Otitis Media

Cholesteatoma

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20
Q

Otosclerosis

A

Bone growth around stapes footplate, “locking” stapes in place

Increases stiffness, creating low-frequency hearing loss

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21
Q

Otitis Media

A

Fluid in middle ear space builds up due to negative pressure

Increases stiffness
- Smaller air space, reduces compliance

Creates low-frequency hearing loss

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22
Q

Cholesteatoma

A

Skin growth that occurs in middle ear space (extra tissue)

Bad cases can destroy ossicles (or require surgery that destroys ossicles)

Loss of ossicles can create a ~60 dB conductive (outer/middle ear hearing loss)

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23
Q

Structures of Inner Ear

A

Vestibular system (sense of balance)
Cochlea
- Primary auditory organ of inner ear
Bony labyrinth/spinal lamina
- Series of tunnels within which membranous labyrinth is housed

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24
Q

Semicircular canals

A

Contain the membranous semicircular ducts
- Sense organs for balance/movement of body in space
Detect angular acceleration (rotation)
Each duct detects motion in a different plane

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25
Q

Cochlear potentials

A

The hair cells and auditory nerve create biochemical electrical potentials

Relies on the flow of potassium and sodium

The motions and interactions of the cochlear structures create electric potentials

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26
Q

DC (direct current) potentials

A

Baseline potential changes that do not change once they happen

dominantes at high frequencies

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27
Q

AC (alternating potentials)

A

Change as a function of the vibrating tissue in the cochlea
dominates at low frequencies

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28
Q

Endolymph and perilymph in cochlea

A

Produce a +8- mV potential difference

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29
Q

Resting Potential Located in the endolymph of scala media and created by the stria vascularis

A

+80 mV

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30
Q

Hair cell receptor potential (inside cell)

A

-40 to -70 mV

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31
Q

Process of increasing afferent activity

A

When the stapes pulls OUT, the BM pulls UP → hair cells tilt toward the tallest stereocilia → tip links open → depolarizes cell → increases afferent activity

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32
Q

Process of increasing efferent activity

A

When the stapes pushes IN, the BM pushes DOWN → hair cells tilt away from the tallest stereocilia → top links closed → hyperpolarizes cell → decreases afferent activity

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33
Q

Outer hair cells Method of Shearing

A

OHC stereocilia is firmly attached to the tectorial membrane
Movement of the BM physically shears OHC stereocilia

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34
Q

Inner hair cells Method of Shearing

A

IHC stereocilia is not attached to the tectorial membrane

Fluids trapped between stereocilia and tectorial membrane cause IHC shearing

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35
Q

OHC loss

A

Causes a significant loss in frequency sensitivity resolution and elevated thresholds

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36
Q

IHC loss

A

Action potential can’t be sent
Therefore the sound can’t be heard

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37
Q

Otoacoustic emissions (OAE)

A

With a microphone in the ear canal, you can record sounds that are different than what you put in (or in the absence of sound)

Non-invasive measure of cochlear function in humans

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38
Q

Types of OAEs

A

Stimulus-frequency OAEs
Transient evoked OAEs
Distortion-product OAEs
Spontaneous OAEs

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39
Q

Stimulus-frequency OAEs

A

Input: long duration tone
Emission: energy at same frequency
Benefit: place specific on basilar membrane
Disadvantage: hard to separate emissions from stimulus (not used clinically yet)

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40
Q

Transient evoked OAEs

A

Input: click
Emission: energy at many frequencies
Benefit: easy to seperate emission from stimulus in time
Disadvantage: not place specific on basilar membrane

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41
Q

Distortion-product OAEs

A

Input: two long duration tones (f1< f2)
Emission: energy at new frequency (2f1-f2)
Benefit: easy to separate emission from stimulus in frequency
Disadvantage: several sources

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42
Q

Spontaneous OAEs

A

Input: no sound
Emission: energy at particular frequencies
Benefit: presence suggests no gross cochlear pathology
Disadvantage: absence doesn’t say much

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43
Q

Central Auditory Pathway

A

Auditory cortex (UPPER)
Medial geniculate body (MGB)
Inferior colliculus
Lateral lemniscus
Superior olivary complex
Cochlear nucleus
Auditory nerve (LOWER)

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44
Q

Action potential generation

A

A stimulus must be intense enough to reach the threshold and an action potential will be generated “all or nothing”

The action potential will have the same duration and intensity

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45
Q

Stages of sodium-potassium pump process for action potential

A

Depolarization
Repolarization
Hyperpolarization

Need the sodium-potassium pump to change the charge of cell membrane

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46
Q

Depolarization

A

Goes from resting potential to threshold
Na+ channels open, some K+ channels open

Increacreased impulse frequency
Cell becomes more positive

47
Q

Repolarization

A

Going back down to become polarized and overshoots
Na+ channels close, K+ channels all open

48
Q

Hyperpolarization

A

Becomes more polarized compared to resting point
K+ channels close, though there is still some K+ leaking in/out

Decreased impulse frequency

49
Q

Two types of refractory periods

A

Absolute refractory period (B-C)

Relative refractory period (C-D)

50
Q

Absolute refractory period (B-C)

A

After a spike is generated, the neuron must recover

For a short period of time, no additional spikes can be generated

51
Q

Relative refractory period (C-D)

A

During hyperpolarization phase

Require a higher intensity stimulus

For a longer period of time, additional spikes are possible but are more difficult to generate and less likely to occur

52
Q

Spontaneous rate of a neuron

A

rate that a neuron will fire in the absence of any auditory stimulus

Determined which intensity range that a neuron can respond to with a change in firing rate

53
Q

Frequency selectivity of AN (tuning curve)

A

Tuning curve becomes broader for higher ampitudes

High CF-outside
Lower CF- center

54
Q

Place theory

A

frequency of the input can be determined by noting which nerve fiber (place) within the AN discharges with the greatest relative discharge rate

Outside of the AN bundle (basal-high frequency)
Middle of the AN bundle (apex-low frequency)

55
Q

Phase locking

A

ability of neuron to synchronize firing to a particular phase of stimulus

Neurons will most likely fire at peaks of stimulus

56
Q

Volley theory

A

Combining spikes across multiple fibers fills in temporal code

Group of neurons together can fire at each cycle of stimulus

57
Q

High SR (spontaeouns rate) neurons

A

low threshold of intensity

58
Q

Low SR neurons

A

high threshold of intensity

59
Q

Auditory Brainstem Responses (ABR)

A

Sequence of waves generated at increasingly higher levels of the auditory system

Used to diagnose pathologies at different sites
- Based on amplitudes and latencies of each individual wave

60
Q

Wave I

A

Auditory nerve

61
Q

Wave II

A

Cochlear nucleus

62
Q

Wave III

A

Superior olivary complex

63
Q

Wave IV

A

Lateral lemniscus

64
Q

Wave V

A

Inferior colliculus

65
Q

Excitation

A

additive
Reinforce neuron activities

E-E: Add together and increase firing rate a lot

66
Q

Inhibition

A

subtractive
Cancel neuron activities

I-E: Final result will depend on magnitude

67
Q

Cochlear Nucleus

A

Tonotopic
ventral (front)= low frequencies
dorsal (back) = high frequencies

Outputs to
superior olivary complex (SOC)
lateral lemiscus (LL)
inferior colliculus (IC)

68
Q

SOC (Superior olivary complex)

A

Three parts
- Lateral superior olive (LSO)
- Medial superior olive (MSO)
- Medial nucleus of the trapezoid (MNTB)

First point of decussation (crossing over to other hemisphere)
First point of binaural processing

Output
- Efferent to CN
- Afferent to LL and IC

69
Q

Lateral Limniscus (LL)

A

Three nuclei
- Ventral (VLL)
- Intermediate (ILL)
- Dorsal (DLL)

70
Q

Which central auditory system structures are at the pons level?

A

SOC and LL

Input
- From CN and SOC
- Efferent input from inferior colliculus

Output
- Efferent to SOC and CN
- Afferent to Inferior Colliculus (IC)

71
Q

Inferior Colliculus (IC)

A

First structure with core and belt organization
Core: auditory- central nucleus
Belt: somatosensory-dorsal cortex and dorsomedial and lateral nuclei

Refining sound localization

Inputs
- Contralateral IC

Outputs
- Efferent to SOC
- Afferent to medial geniculate body

72
Q

Medial Geniculate Body (MGB)

A

at level of thalamus
Core: ventral (MGBv)-auditory
Belt: dorsal (MGBd) and medial (MGBm)-somatosensory and auditory

Lateral: high frequency
Medial: low frequency

Input
- From IC
- Core to core, belt to belt

Output
- To auditory cortex

73
Q

Auditory Cortex

A

Posterior 2/3 of superior temporal gyrus

Core: primary AC (A1)
Belt: secondary AC (A2)

anterior= responding to sounds in front of us
posterior= responding to sounds behind us

Efferent projections from AC to MGB and IC

74
Q

Contralateral bias

A

Majority of auditory nerve fibers project to contralateral structures

75
Q

Auditory Nerve (CN VIII)

A

Bilateral structures and pathways with contralateral dominance

Formed by twisting of Type I and Type II neurons
Low frequency neurons in center
High frequency neurons toward periphery (tonotopic)

76
Q

Hair cells

A

sensory cells of the inner ear

77
Q

Tectorial membrane

A

gelatinious structure that the OHC stereocillia are embedded

78
Q

Helicotrema

A

very apex of the cochlea

79
Q

Stria vascularis

A

dense layer of blood capillaries on the side of the scala media that supplies metabolic energy to the cochlea

80
Q

Basilar membrane

A

stiff structural element within the cochlea that separates the scala media and scala tympani

supports the organ of Corti

floor of scala media

81
Q

Modiolus

A

the central axis around which the cochlear spiral winds

82
Q

Organ of corti

A

the organ that sits atop of the basilar membrane and contains the outer hair cells and inner hair cells

83
Q

Reissner’s membrane

A

Separates perilymph of scala vestibuli and endolymph of scala media

84
Q

Parts of the Vestibular System (Balance and Movement)

A

Otolith organs
Saccule
Semicircular canals

85
Q

Parts of the Auditory System

A

Cochlea
Organ of Corti

86
Q

Parts of Both (Vestibular and Auditory Systems)

A

Endolymph
CN VIII (auditory nerve)
Hair cells

87
Q

Middle ear function

A

impedance matching, selective oval window stimulation, pressure equalization

88
Q

Inner ear function

A

filtering, distribution, transduction

89
Q

Inner ear structures

A

Semicircular canals
Vestibule
Vestibular notch
Cochlea
Round window
Eustachian tube

90
Q

Impedance factors

A

stiffness, mass, damping (friction)

91
Q

stiffness

A

Most relevant at low frequencies

92
Q

mass

A

Most relevant at high frequencies

93
Q

Damping (friction)

A

Most relevant at medium frequencies where mass and stiffness cancel each other

94
Q

scala media

A

Function: hearing
Located between scala vestibuli and scala tympani

95
Q

Type I AN afferent fibers

A

Larger
Myelinated
Innervate IHCs exclusively
Many to one, one to one

96
Q

Type II AN afferent fibers

A

Smaller
Unmyelinated
Innervate OHCs (one to many)
5% of afferents forming the auditory nerve

97
Q

Single-cell cochlear potentials

A

Voltage inside a single cell
- Hair cells
- Auditory nerve fibers (and other neurons are higher up)

Resting potential
- DC potential in the absence of stimulation (typically -60 mV)

Action potential
- A sharp and rapid peak (depolarization inside auditory nerve fibers that occurs after the potential reaches a threshold)

98
Q

Gross cochlear potentials

A

Combined electrical activity from many individual cells (summed currents cause potentials)

Can be measured clinically

99
Q

Saturation

A

stage a nerve fibers reaches when the maximum firing rate has been reached and continues to fire at the maximal level without further increasing its potential

100
Q

Which direction of basilar membrane movement causes OHC depolarization to occur?

A

upward displacement

101
Q

Which structures contain perilymph?

A

scala vestibuli
scala tympani

102
Q

High sensitivity (feature of auditory nerve fibers)

A

allows useful spectral features to be discriminated

103
Q

Sharp tuning (feature of auditory nerve fibers)

A

allows soft sounds to be detected

104
Q

Distortion-product OAEs (DPOAEs)

A

emission that occurs from presenting two tones of different frequencies into the air and getting out a tone of a different frequency

105
Q

Neural threshold

A

when this threshold is reached, a neuron will start firing above its spontaneous rate

106
Q

Stereocilia

A

hairs that are found on top of the inner and outer hair cells and are bathed in endolymph

107
Q

Transient evoked OAEs (TEOAEs)

A

this emission is recorded using a click as a stimulus

108
Q

Intensity coding

A

an increase in regular firing rate that occurs with an increase in intensity

109
Q

Tip links

A

filaments that connect stereocilia to each other or to the kinocilium in the hair cells of the inner ear

110
Q

Isointensity curve

A

a chart measuring an auditory nerve fiber’s firing rate to a wide range of frequencies, all presented at the same intensity level

Y-axis: spikes/per second
X-axis: input stimulus level (dB SPL)

111
Q

Endocochlear potential

A

the positive voltage of 80-100 mV seen in the endolymphatic spaces

112
Q

Round window

A

structure in the middle ear space that moves opposite the oval window to maintain the cochlear volume

113
Q

Characteristics of the basilar membrane at the apex level (low frequencies)

A

loose and wide
processes low frequency sounds
contains auditory nerve fibers of all spontaneous rates

114
Q

Synaptopathy

A

phenomenon where there is temporary damage to OHCs but permanent damage to auditory nerve fibers/synapses that likely affects speech intelligibiliy in noise

SLHS 302 (3 decks)

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