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SLHS 302 > Exam 2 > Flashcards

Exam 2 Flashcards

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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
Cochlear potentials
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
26
DC (direct current) potentials
Baseline potential changes that do not change once they happen dominantes at high frequencies
27
AC (alternating potentials)
Change as a function of the vibrating tissue in the cochlea dominates at low frequencies
28
Endolymph and perilymph in cochlea
Produce a +8- mV potential difference
29
Resting Potential Located in the endolymph of scala media and created by the stria vascularis
+80 mV
30
Hair cell receptor potential (inside cell)
-40 to -70 mV
31
Process of increasing afferent activity
When the stapes pulls OUT, the BM pulls UP → hair cells tilt toward the tallest stereocilia → tip links open → depolarizes cell → increases afferent activity
32
Process of increasing efferent activity
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
33
Outer hair cells Method of Shearing
OHC stereocilia is firmly attached to the tectorial membrane Movement of the BM physically shears OHC stereocilia
34
Inner hair cells Method of Shearing
IHC stereocilia is not attached to the tectorial membrane Fluids trapped between stereocilia and tectorial membrane cause IHC shearing
35
OHC loss
Causes a significant loss in frequency sensitivity resolution and elevated thresholds
36
IHC loss
Action potential can’t be sent Therefore the sound can’t be heard
37
Otoacoustic emissions (OAE)
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
38
Types of OAEs
Stimulus-frequency OAEs Transient evoked OAEs Distortion-product OAEs Spontaneous OAEs
39
Stimulus-frequency OAEs
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)
40
Transient evoked OAEs
Input: click Emission: energy at many frequencies Benefit: easy to seperate emission from stimulus in time Disadvantage: not place specific on basilar membrane
41
Distortion-product OAEs
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
42
Spontaneous OAEs
Input: no sound Emission: energy at particular frequencies Benefit: presence suggests no gross cochlear pathology Disadvantage: absence doesn’t say much
43
Central Auditory Pathway
Auditory cortex (UPPER) Medial geniculate body (MGB) Inferior colliculus Lateral lemniscus Superior olivary complex Cochlear nucleus Auditory nerve (LOWER)
44
Action potential generation
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
45
Stages of sodium-potassium pump process for action potential
Depolarization Repolarization Hyperpolarization Need the sodium-potassium pump to change the charge of cell membrane
46
Depolarization
Goes from resting potential to threshold Na+ channels open, some K+ channels open Increacreased impulse frequency Cell becomes more positive
47
Repolarization
Going back down to become polarized and overshoots Na+ channels close, K+ channels all open
48
Hyperpolarization
Becomes more polarized compared to resting point K+ channels close, though there is still some K+ leaking in/out Decreased impulse frequency
49
Two types of refractory periods
Absolute refractory period (B-C) Relative refractory period (C-D)
50
Absolute refractory period (B-C)
After a spike is generated, the neuron must recover For a short period of time, no additional spikes can be generated
51
Relative refractory period (C-D)
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
Spontaneous rate of a neuron
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
Frequency selectivity of AN (tuning curve)
Tuning curve becomes broader for higher ampitudes High CF-outside Lower CF- center
54
Place theory
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
Phase locking
ability of neuron to synchronize firing to a particular phase of stimulus Neurons will most likely fire at peaks of stimulus
56
Volley theory
Combining spikes across multiple fibers fills in temporal code Group of neurons together can fire at each cycle of stimulus
57
High SR (spontaeouns rate) neurons
low threshold of intensity
58
Low SR neurons
high threshold of intensity
59
Auditory Brainstem Responses (ABR)
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
Wave I
Auditory nerve
61
Wave II
Cochlear nucleus
62
Wave III
Superior olivary complex
63
Wave IV
Lateral lemniscus
64
Wave V
Inferior colliculus
65
Excitation
additive Reinforce neuron activities E-E: Add together and increase firing rate a lot
66
Inhibition
subtractive Cancel neuron activities I-E: Final result will depend on magnitude
67
Cochlear Nucleus
Tonotopic ventral (front)= low frequencies dorsal (back) = high frequencies Outputs to superior olivary complex (SOC) lateral lemiscus (LL) inferior colliculus (IC)
68
SOC (Superior olivary complex)
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
Lateral Limniscus (LL)
Three nuclei - Ventral (VLL) - Intermediate (ILL) - Dorsal (DLL)
70
Which central auditory system structures are at the pons level?
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
Inferior Colliculus (IC)
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
Medial Geniculate Body (MGB)
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
Auditory Cortex
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
Contralateral bias
Majority of auditory nerve fibers project to contralateral structures
75
Auditory Nerve (CN VIII)
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
Hair cells
sensory cells of the inner ear
77
Tectorial membrane
gelatinious structure that the OHC stereocillia are embedded
78
Helicotrema
very apex of the cochlea
79
Stria vascularis
dense layer of blood capillaries on the side of the scala media that supplies metabolic energy to the cochlea
80
Basilar membrane
stiff structural element within the cochlea that separates the scala media and scala tympani supports the organ of Corti floor of scala media
81
Modiolus
the central axis around which the cochlear spiral winds
82
Organ of corti
the organ that sits atop of the basilar membrane and contains the outer hair cells and inner hair cells
83
Reissner’s membrane
Separates perilymph of scala vestibuli and endolymph of scala media
84
Parts of the Vestibular System (Balance and Movement)
Otolith organs Saccule Semicircular canals
85
Parts of the Auditory System
Cochlea Organ of Corti
86
Parts of Both (Vestibular and Auditory Systems)
Endolymph CN VIII (auditory nerve) Hair cells
87
Middle ear function
impedance matching, selective oval window stimulation, pressure equalization
88
Inner ear function
filtering, distribution, transduction
89
Inner ear structures
Semicircular canals Vestibule Vestibular notch Cochlea Round window Eustachian tube
90
Impedance factors
stiffness, mass, damping (friction)
91
stiffness
Most relevant at low frequencies
92
mass
Most relevant at high frequencies
93
Damping (friction)
Most relevant at medium frequencies where mass and stiffness cancel each other
94
scala media
Function: hearing Located between scala vestibuli and scala tympani
95
Type I AN afferent fibers
Larger Myelinated Innervate IHCs exclusively Many to one, one to one
96
Type II AN afferent fibers
Smaller Unmyelinated Innervate OHCs (one to many) 5% of afferents forming the auditory nerve
97
Single-cell cochlear potentials
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
Gross cochlear potentials
Combined electrical activity from many individual cells (summed currents cause potentials) Can be measured clinically
99
Saturation
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
Which direction of basilar membrane movement causes OHC depolarization to occur?
upward displacement
101
Which structures contain perilymph?
scala vestibuli scala tympani
102
High sensitivity (feature of auditory nerve fibers)
allows useful spectral features to be discriminated
103
Sharp tuning (feature of auditory nerve fibers)
allows soft sounds to be detected
104
Distortion-product OAEs (DPOAEs)
emission that occurs from presenting two tones of different frequencies into the air and getting out a tone of a different frequency
105
Neural threshold
when this threshold is reached, a neuron will start firing above its spontaneous rate
106
Stereocilia
hairs that are found on top of the inner and outer hair cells and are bathed in endolymph
107
Transient evoked OAEs (TEOAEs)
this emission is recorded using a click as a stimulus
108
Intensity coding
an increase in regular firing rate that occurs with an increase in intensity
109
Tip links
filaments that connect stereocilia to each other or to the kinocilium in the hair cells of the inner ear
110
Isointensity curve
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
Endocochlear potential
the positive voltage of 80-100 mV seen in the endolymphatic spaces
112
Round window
structure in the middle ear space that moves opposite the oval window to maintain the cochlear volume
113
Characteristics of the basilar membrane at the apex level (low frequencies)
loose and wide processes low frequency sounds contains auditory nerve fibers of all spontaneous rates
114
Synaptopathy
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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