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101 Cards in this Set
- Front
- Back
The inner ear includes the following structures
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vestibule
scala tympani basilar membrane |
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Which of the following structures inside cochlea houses the hair cells?
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*scala media
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The basilar membrane is
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*narrow and stiff at the base (high frequencies)and wide and flexible at the apex (low frequencies)
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The cochlear coils about
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2 1/2
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The hair cells are sandwiched by
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the basilar membrane and tectorial membrane
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Select the best answer from the following statements about BM responses to tones
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The basal end has max response to high frequency tones and the apical end to low frequency tones
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The vast majority of the auditory nerve fibers have synaps on
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inner hair cells
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Which of the following structures will respond to a tone at its frequency?
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Basilar membrane
inner hair cells stapes and outer hair cells |
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Which of the following is responsible for the frequency analysis by the basilar membrane?
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Different parts of the basilar membrane have different resonant frequencies
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Which of the following structure is likely the source of the endocochlear potential?
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stria vascularis
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The relative motion between the tectorial membrane and the basilar membrane leads to
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the bending of the OHC cilia and the OHC depolarization
the bending of the IHC cilia and the IHC depolarization the OHC motility and the release of neurotransmitter in the IHC |
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Which of the following potentials appear in the absence of acoustic stimulation?
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resting potential
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The potential difference across the top of the hair cells between the inside and outside of the hair cells is
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150mV
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.While the ___ serve to enhance sensitivity and frequency selectivity the ___ serve a role in sensory transduction for hearing
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OHCs; IHCs
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Clicks are used to measure
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TEOAEs
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About 90% of afferent fibers are ____ fibers and they innervate _____
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Type 1; IHCs
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In human cochlea, each auditory nerve innervates mostly ______ IHC(s) and each IHC receive ____ auditory nerve(s)
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one; eight
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Within the nerve bundle leaving the cochlea
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the ANs innervating low frequency are in the middle
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A Rate-Level function of an AN includes the following information
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Spontaneous discharge rate
Saturation discharge rate Dynamic rage of a single nerve |
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Choose the correct statement from the following:
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ANs with high spontaneous rate tend to have low threshold
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Tuning curve of a single nerve reflects
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How sharply the nerve is tuned to its best frequency
The stimulus level needed to excite a fixed discharge rate at different frequencies the frequency selectivity of the BM responses to sounds |
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The neural representation of stimulus spectrum is called
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an excitation pattern
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The entire range of audible sound intensity is likely encoded in the auditory system by
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the discharge rate of ANs with different spontaneous rates and different best frequencies
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The sound frequency is encoded in auditory nerve by
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a place code
a temporal code |
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What are the four pieces of information that one can obtain from a rate level function?
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Spontaneous rate, threshold, dynamic range and saturation)
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How does the neural-response threshold depend on the spontaneous response rate?
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High SR – Low TH)
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List three pieces of information that a tuning curve shows?
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Best Freq; sensitivity; sharpness
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What is the ‘dynamic-range problem’ in hearing?
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Single nerve only covers 30 dB but all of hearing is 120 dB)
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How does the auditory system overcome the dynamic-range problem, list two mechanisms?
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1. Combine fibers at same best frequencies with different thresholds
2. Combine fiber at different best frequencies with same thresholds |
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What is the basis for the place coding of stimulus frequency?
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Place theory- frequency mapped to place on basilar membrance
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What is the basis for the temporal coding of stimulus frequency?
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Temporal theory- frequency represented by temporal pattern of discharges
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Which histograms of auditory nerve discharge shows the neural activity can follow the temporal variation of the stimulus amplitude?
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(PST, period, and interval
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List four pieces of information or characteristics that can be observed in a PST histogram in response to a steady tone.
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Spontaneous activity, Onset response, adaptation and recovery
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In a two-tone suppression, describe what happens to the neural response to a primary tone is affected when a second tone at an adjacent frequency is introduced.
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reduction of discharge rate
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What combinations of level and frequency for the second tone are necessary for two-tone suppression to occur?
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Hint: remember the tuning curve with a shaded area on each side} (Look for the shaded region and if the tone is in that level of frequency and level of dB it will mask it)
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What is the significance in auditory function of two-tone suppression?
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masking
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(Very Important) Describe the sequence of events that takes place in the inner ear during sound stimulation from the stapes to the auditory nerve.
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(Stapes vibrates, fluid vibrates, Basilar Membrane vibrates, bends outside hair cells and OHC depolarizes and contracts and expands, pumps energy back to BM energy picked up by Inner Hair Cells, depolarizes inner hair cells leads to release of neurotransmitter)
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What is the fluid and the potential inside the scala media?
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Endolymph; +80 mV
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Of which ion does the fluid (endolymph) have a high concentration
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potassium K+
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What is the fluid and potential inside the other two scalas: vestibular and tympani?
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(Perilymph)
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Of which ion does the fluid (perilymph) have a high concentration?
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sodium Na+
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What is the resting potential inside the hair cells?
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-70mV
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Describe how the physical properties (width and stiffness) and the resonant frequency change along the basilar membrane
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(Stiff and narrow near base, tuned to high frequencies)
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What the typical length of a human cochlear
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35mm
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Which OAE is evoked by clicks
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TEOAE
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Which OAE is evoked by a pair of tones?
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DPOAE
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The vast majority of the auditory afferent nerves are of this type of nerve fibers
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type 1
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On which hair cells do these fibers have synapses
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IHCs
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Which hair cells receive about 90% afferent fibers?
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IHCs
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From how many IHCs does each auditory nerve receive input?
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one
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Within the nerve bundle leaving the cochlea, to what frequencies are the nerves in the middle tuned?
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low frequencies
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What are the two major functions of the OHC amplification?
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(Sensitivity and frequency selectivity)
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Which two hearing abilities will be affected by damages to the OHCs?
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Lose sensitivity and frequency selectivity will not be as sharp and lose low sounds first
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What is the major function of the IHCs
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Transduction from mechanic vibration to neural activity
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What is the major function of the IHCs
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Transduction from mechanic vibration to neural activity
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What happens to the hearing in a frequency region where the OHC are intact but the IHCs are gone?
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No hearing
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During sound stimulation, what causes the stereocilia to bend
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Relative motion between BM and TM)
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Why does the BM have the max response to low frequency tones near the apical end, and a max response to high frequency tones near the basal end?
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resonance
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What are the two arguments supporting that BM traveling wave is not the same kind of traveling wave as the travels on a long rope after a person shakes it at one end?
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If you cut it and it does not need to go away from its source)
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The relative motion between the TM and the BM leads to bending cilias
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which leads to depolarization
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Why is the Alternating Current component of the cochlear potential the “cochlear microphonic”?
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Because you can hook it up to a PA system
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What is the potential difference across the top of the hair cells between the inside and outside of the hair cells?
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150mV +80 -70
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List the major outer and middle ear structures (that are of functional importance) in the correct order from pinna to oval window.
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(Pinna, cocha, ear canal, tympanic membrane, three ossicles, oval/round windows; middle ear ligaments/ muscles; E. tube)
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What is the amount of the maximum boost in dB to the sound due to the ear-canal resonance?
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10-15dB
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What is the frequency of maximum boost due to the ear canal
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2-3 kHz
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What is the maximum boost in dB to the sound due to the concha resonance
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10 dB
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What is the frequency of that maximum concha resonance
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5 kHz
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What is the primary function of the middle ear?
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overcome impedance
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Describe the three middle-ears mechanisms that contribute to overcoming mismatch of impedance.
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Area 25 dB; lever 2 dB, buckling motion 6 dB
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What is the amount of the peak of max gain in DB that the middle ear transfer function shows?
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30 dB
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At what frequency does the middle ear transfer function show the max gain
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1000 Hz
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What is the primary function of the E tube
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Equalizing pressure
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Due to the presence of pinna, sounds coming from different directions will be affected differently upon reaching the eardrum. In which aspect does the pinna cause the sounds to change?
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Spectral shape
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During sound stimulation, what causes the stereocilia to bend?
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Relative motion between BM and TM)
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Boost due to sphere head
Why there is a boost? |
constructive interaction
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How many dBs is the boost for a sphere head?
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5dB
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What frequency region has the boost for sphere head
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> 500Hz
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How is it done localization?
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A change in the sound direction will cause a change in spectral shape, particularly at high frequencies
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What’re the limitations of the hearing protection that the middle-ear muscles can provide?
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Contraction in responding to loud sound to protect hearing
-reduction in transmission of loud sound by 10-30 dB |
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Auditory (Eustachian) tube Audult vs. Infant
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Infant is more horizontal and leads to more ear infections.
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The Ossicles apply force to only one window
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oval window
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What’re the limitations of the hearing protection that the middle-ear muscles can provide?
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10 to 30 dB; only from very loud sound; slow to react
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Why is it important to pass the sound to only one window but not both oval and round window?
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cochlear fluid is incompressible, thus when one window is pushed in, the other window must be going out
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Describe how hair cells are positioned along the BM within the organ of corti.
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Three rows of OHCs and one row of IHC along the BM
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Organ of Corti
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Hair Cells: 3 rows of OHC 1 row of IHC. supporting hair cells. surrounded by tectorial membrane
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When a tone vibrates the stapes, how does the stapes stimulate each point along the BM?
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The stapes stimulates every point simultaneously
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Describe how OHC amplifies the BM response to sound
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1. The initial motion of BM will set off the OHC to dance
2. The OHC ‘dance’ pumps energy back into the BM and amplifies its motion 3. The enhanced BM motion is much more easily detected by the IHC |
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What voltages are the three resting potentials?
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1. EP: +80 mV;
2. Intracellular: -70 mV; 3. extracellular: 0 mV |
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What are stimulus evoked potentials?
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CM, ac; mostly from OHCs; it follows the stimulus frequency
SP, dc; from multiple sources |
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Disturbance/motion OAE
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* originated on BM vibration of cochlear fluid vibrations of the ossicles and tympanic membrane sound in the ear canal
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How many Type I fibers innervate each IHCs?
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many to one
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Where do efferent fibers make connections?
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directly on the OHCs, and indirectly via afferent fiber on the IHCs
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Inside the nerve bundle within the modiolus wall, how are the AN fibers organized according to their best frequencies?
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low-freq fibers in the center; high-frequency fibers on the outside
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What’s in a PST histogram?
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SOAR: spontaneous activity, onset response, adaptation, recovery
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Neural Rate-Intensity Function
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spontaneous rate, dynamic range= staturation - thershold
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Three Types of Neurons
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Low-SR (< 0.5 Spikes/sec): High thresh
Med-SR (0.5 <SR < 18 s/s): Med thresh High-SR (> 18 s/s): Low thresh |
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What is the limit for a nerve’s discharge rate?
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1000 spikes/sec
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Why is the discharge rate limited to 1000 S/s?
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because action potential has a refractory period of about 1 ms, during which no two spikes are allowed
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Tuning Curve
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place coding:A frequency to place mapping; each nerve carries info about a specific place or frequency
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Temporal
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: The temporal pattern of spikes (e.g., interval histogram) encodes stimulus frequency and pitch
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Place:
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The peak of the BM excitation, as reflected in the AN responses, encodes stimulus frequency and pitch
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