Term
| When stereocilia bends in the excitatory direction the tip links... |
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Definition
| open K+ channels within the stereocilia and allow more K+ ions to enter the cell. |
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Term
| When the K+ channels are opened and more K+ ions enter the cell this... |
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Definition
| depolarizes the cell, sets up action potential, with a subsequent neurotransmitter release, and eventual stimulation of the afferent nerve fibers. |
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Term
| When a hair cell is depolarized what type of nerve fibers are stimulated? |
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Definition
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Term
| When the stereocilia bend in the inhibitory direction the tip links... |
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Definition
| close the K+ channels within the stereocilia, allowing no more K+ to enter the hair cells. |
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Term
| Once the K+ channels of the stereocilia are closed The K+ that entered during depolarization is... |
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Definition
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Term
| The majority of afferent cells are attached to which type of hair cells? |
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Definition
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Term
Since the majority of afferent nerve cells
are attached to the IHCs, we know that the inner hairs are responsible for...
inner hair cells are thus responsible for |
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Definition
| sending acoustic messages to the brain |
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Term
| In order to send acoustic messages to the brain the IHC's must communicate with... |
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Definition
| the dendrites of the VIIIth nerve fibers |
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Term
| Chemical to neural transmission occurs between... |
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Definition
| the IHC membrane and the dendrites of the afferent VIIIth cranial nerve. |
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Term
with the
depolarization of the hair cell during the excitatory
phase, neurotransmitter is released into the... |
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Definition
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Term
| Once the neurotransmitter reaches a graded potential... |
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Definition
it will cause the VIIIth nerve fiber to fire. This “firing” of the nerve
fibers causes a chain reaction of neural
firing that travels from the VIIIth nerve,
through the brainstem auditory nuclei, to
the brain. |
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Term
| The "firing" of the fibers of the VIIIth nerve causes... |
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Definition
a chain reaction of neural
firing that travels from the VIIIth nerve,
through the brainstem auditory nuclei, to
the brain. |
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Term
| Each time a nerve fiber fires it can be recorded as a... |
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Definition
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Term
| During the excitatory phase neurotransmitter is released into the... |
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Definition
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Term
| Neurotransmitter is released into the synaptic cleft during which phase? |
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Definition
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Term
| Describe: Graded Potential |
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Definition
| once the released neurotransmitter reaches a "critical mass it is said to have reached it's graded potential. This causes the nerve fibers to fire which causes a chain reaction of neural firing that travels from the VIIIth nerve through the brainstem nuclei, to the brain |
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Term
| Once the released neurotransmitter reaches it's graded potential it causes the VIIIth nerve to fire creating a chain reaction which travels... |
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Definition
| from the VIIIth Nerve throug the brainstem auditory nuclei to the brain. |
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Term
| How do we measure an how an VIIIth Nerve fiber responds? |
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Definition
| each time the nerve fiber fires is can be recorded as a spike and all spikes have the same amplitude and duration. Thus the info conveyed is how many spikes occur in a given time period and at what location these spikes are occurring. |
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Term
| The information conveyed by "spikes"? |
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Definition
| How many occur in a time a given time period and the location at which the occur. |
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Term
| All spikes have the same? |
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Definition
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Term
| Tuning of the basilar membrane or VIIIth Nerve refers to? |
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Definition
| the sensitivity of these structures to particular frequencies and how much pressure it takes to get a response. |
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Term
| Tuning curves are a way to? |
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Definition
| display the response of a location on the basilar membrane by it's displacement, and an VIIIth Nerve by it's firing rate. |
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Term
| Tuning Curves measure the response of a location on the basilar membrane by it's _______ and on the VIIIth Nerve by it's ______ _____. |
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Definition
| displacement, firing rate |
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Term
| The first measurement we make using the tuning curve is the... |
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Definition
| characteristic frequency (CF) or the frequency that takes the least sound pressure for the nerve fiber to respond. |
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Term
| Define: Characteristic Frequency (CF) |
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Definition
| The frequency that takes the least sound pressure for that nerve fiber to respond. That is the fiber has a clear sensitivity to that frequency. |
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Term
| The shape of tuning curves (TC) is developed |
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Definition
| by plotting a pre-determined response threshold to a number of frequencies. That is, to what frequencies will a fiber or cell respond and how much pressure does it take to see a response. |
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Term
| What is believed to be responsible for the narrow tuning of the VIIIth Nerve Fibers? |
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Definition
| The motility of the outer hair cells, which influences the response at a particular place on the basilar membrane and most likely stimulates the inner hair cells to respond. |
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Term
| What are the theories on how we place code? |
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Definition
| Place Theory, Frequency Theory |
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Term
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Definition
| A theory on how frequency is coded; the system initially codes frequency by where the peak of the traveling wave occurs on the basilar membrane (HF's: base, LF's: apex). This information is preserved all along the auditory pathway from the basilar membrane to the brain since each auditory nuclei is tonotopically organized. (Not a complete Theory) |
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Term
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Definition
| A theory about how we code frequency; for frequencies below 1000Hz the frequency can be coded by how many times a nerve fiber fires per second. However, due to the refractory period, nerve fibers cannot fire faster than 1000 times per second. So for frequencies higher than 1000Hz phaselocking comes in. |
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Term
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Definition
| We can theorize that a nerve fiber does not have to fire with every cycle of a frequency to code that frequency. Rather if a nerve fiber fires at the same point every other cycle or few cycles it can still code he essence of that frequency. |
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Term
| There appear to be shortcomings which which theory of frequency coding? |
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Definition
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Term
| It is common thinking that frequency coding is accomplished by a combination of... |
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Definition
| place and timing or phaselocking behavior that allows the nerve to signal the intended frequency. |
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Term
| What is the theory behind Intensity Coding? |
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Definition
| that with more the basilar membrane movement due to a loud sound, the greater the number of hair cells, and thus nerve fibers are activated. Up to approximately 40dB, the firing rate of neurons will increase with increasingly louder sounds. |
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Term
| Describe: Staggered Intensity Thresholds |
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Definition
| It has been suggested that not all neurons hat impinge on an IHC respond with the same threshold; that is, there ma be some that respond at softer levels and others that don't respond until a signal is at least 60-70 dB. |
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