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67 Cards in this Set
- Front
- Back
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definition of sound
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sinusoidal oscillations(waves) of air compressions and rarefractions in an elastic medium
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Human freqency hearing range
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20Hz-->20KHz
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how is loudness measured
for every 10fold inc in amplitude |
on a log scale in Decibels(Db)
we perceive an equal increment in sound |
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Loudness=
Pref |
20 X log(10) P/Pref
threshold of sound detection at best frequency humans=1 KHz |
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damage occurs at
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120dB
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damage to cochlear nucleus leads to
nucleus is not bilaterally innervated, BUT... |
ipsilateral hearing loss
after it leaves, it crosses giving bilateral innervation |
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outer ear
middle ear inner ear |
collects sound
transmission/amplification from ear->cochlea via:incus, malleus, and stapes processes auditory information -converts mech E to elect E |
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in the cochlea
Basilar membrane |
separates scala media and scala tympani, continuous
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Base
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near oval window
narrow in width responds to high freq |
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Apex
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respons to lower freq
looser and resonates better |
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the narrow base to wide apex is the basis for?
dfft sections of the basilar membrane |
Primary Basis for encoding frequencies
respond to dfft frequencies |
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Place Encoding
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freq is encoded by the position of transduction along the basilar membrane
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Scala Media
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contains endolymph- high in K
continuously replinished by Stria Vascularis |
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Stria vascularis
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maintains endolyph in scala media by simply replacing it, not active transport
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Scala Tympani and Scala vestibuli
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have Perilymph
approx conc to regular CSF, low K conc |
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tectorial membrane is on top of what?
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the organ of corti
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Hair cells
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the principle transducing apparatus
1. Outer hair cells 2. inner haircells |
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Inner Hair Cells
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3500 total
more important in hearing -loss is significant respond to primary freq of basilar memb vibration -base=high, apex=low |
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Outer Hair Cells
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14000
loss of these leads to strange alterations in sensitivity |
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what do outer hair cells modulate?
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modulate afferent signal back to the CNS by changing the mechanical properties of basilar membrane
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the main afferent sensory nerve
cell bodies are located where? |
1. runs to spiral ganglion
2. out to cochlear nerve in the spiral ganglion |
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Hair cell has
apical surface basilar suface |
endolymph at apical
perilymph at basilar |
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high conc of K affects what
apical basilar |
depolarizes the apical memb of cell
normally neg potential normally depolarized by K |
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Activation of hair cell
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1. k flows across apical surface
2. voltage dep Ca chann act 3. voltage dep Ca chann also activate Ca sensitive K chan 4. K chan allow k to be pumped across basal surface, out of cell -k transport across entire cell |
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Bundles of cilia
main cilia on top is called |
on apical surface of hair cell
initiate K transport on apical Kinocilium |
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Linkers
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between the cilia are proteinaceous briges
*attached to mechanically operated ion channels |
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mechanical work moves linkers, leads to what?
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1. opening Ion channels and K flows in
2. depolarizes cilia 3. travels down to apical memb 4. depolarizes apical and initiates signal trasduction |
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OHC are attached to what?
what does this mean? |
tectorial membrane
when tect membrane moves there is a mechanical sharing of energy and this pulls cilia channels open |
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encoding via
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different hair cells are more sensitive to different frequencies
tuning freq depends on where its located on basilar membrane |
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most hearing loss is due to?
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hair cell damage
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cochlear implants are successful because
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place encoding for frequency
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how do you replace a loss of all IHC?
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direct stimulation of the afferent nerve by a coiled wire that runs under basilar membrane
only 8 key freq needed for hearing |
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synapsing
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presynaptic membrane has a lot of vessicles
same Ca dependent trandsuction mechanism |
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what is the primary afferent transmitter?
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Glutamate
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what is the ratio for afferent signaling in OHC
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10:1 eff:aff
a lot less afferent signaling NOT part of transmission to auditory system |
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SON sends...
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efferent fibers to OHCs and IHCs
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each inner hair cell has
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1:10 eff:aff
a lot more afferent signals, heavily afferent |
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afferent IHC signaling encodes for
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1. freq
2. loudness 3. location 4. bilateral inputs |
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what is the main role of OHC?
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central regulation is the main function
they are attached to basilar membrane, reamplify signal recover mech E lost by dampening of the media |
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Antimasking suggests that
stimulating what hair cells? |
efferents from CNS do play a role
OHC picks out signals from background noise |
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when OHC are inactive
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flat higher firing rate of IHC at lower frequencies
not detecting tone bursts to level of 50dB |
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when OHC are active
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1. lower firing rate at low freq
2. get antimasking of noise 3. allow detection of tone burst at lower sound intensities 4. allows IHC to have a wider dynamic range |
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Overall:
IHC are OHC are |
primary transducers of sound
regulate the behavior of IHC and sensitivity |
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loudness saturates at
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500 spikes/sec
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Phase Locking
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in the oscilations of a sine wave, we only see things at the peak or trough
peak-opens K chan tough- closes K chan |
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number of APs in the peak rep
space b/w APs represents |
loudness
frequency |
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Localizing Sound
auditory info enters thru |
cochlear nucles, then sends to dfft places, dividing up the qualities: loudness, location,etc
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at the level of the SON, sound travels to the...
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Trapezoid Body
this results in bilat info processing |
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travels through Lateral Lemniscus to..
then to.. |
Inferior Colliculus (wine glass)
medial geniculate of thalmus and finally to auditory cortex |
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sound is localized when
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it reaches one cochlea before the other
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the sound from the opp ear of sound will determine
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what cells the sound will feed into and when it will feed into them
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big delay in sound
shorter delay |
will detect coincidence at more distal cells
will detect coincidence at more proximal cells |
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location of a cell where coincidence is detected allows you to tell?
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how far a sound is displaced from the midline
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Intensity difference is detected
cell responds best when |
by Lateral SON
intensity from ipsilateral side exceeds the other |
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Inferior colliculus is the first place that...
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takes information from BOTH SON and puts it int a map
maps where sounds are directs attention to sound |
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Medial Geniculate nucleus
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auditory nucles in thalmus
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Transverse Temporal Gyrus
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Heschel's Gyrus
on top of temporal lobe Primary auditory cortex |
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Tonotopy, how are they organized?
cells look at dfft... |
based in terms of their freq coding
1. freq 2. location 3. loudness |
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Heschel's Gyrus is near
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Wernicke's gyrus-language processing
sends info to Broca's area |
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where is sound localized?
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inferior colliculus
medial SON |
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at low frequencies what dominates?
at high frequencies what dominates? |
phase locking: only have APs at peaks
freq generate APs at specific locations in the basilar membrane |
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medial SON
lateral SON |
processes location of sound
processes intensity of sound |
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if there is a BIG delay in sound, the coincidence of input is more?
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distal
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if there is a SMALL delay in sound, the coincidence of input is more?
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Proximal
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The Inferior Colliculus (IC) receives
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both medial and lateral SON
integrates both localization and intensity |
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Transvers Temporal Gyri=
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Heschel's gyrus
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Heschel's gyrus demonstrates...
cells look at.. |
Tonotopy- based on freq coding
1. freq 2. location 3. loudness |
