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24 Cards in this Set
- Front
- Back
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An increase of 1 dB is equivalent to what kind of increase in sound pressure?
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Each dB increase means a ten-fold increase in sound pressure.
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What determines the pitch of sound?
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Its frequency.
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What frequencies of sound are audible to humans?
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20-20,000 Hz
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At what frequency do vowels occur? Consonants? How does this explain a loss of the ability to differentiate consonants as seen in presbyacusis?
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*vowels - low frequency
*consonants - high frequency *high frequency discrimination is one of the first things to go in presbyacusis |
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What is a spectrograph? How can the fundamental frequency of a sound be recognized on one?
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*a visual representation of a sound at which the energy at each frequency is depicted
*the fundamental frequency will be that one with the greatest energy |
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What is one of the unique functions of the pinna?
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It helps to determine vertical elevation of sound, one of the few structures to do so.
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What is the essential function of the middle ear?
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It transduces sound energy from air to liquid, while at the same time increasing the force of the vibrations to account for the greater density of fluid.
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What are the two middle ear muscles and where do they insert? What is their function?
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*stapedius - stapes
*tensor tympani - malleus *dampen vibrations to prevent damage |
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What is otosclerosis?
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A proliferation of bone at the foot of the stapes which interferes with its ability to vibrate on the oval window. This causes a conductive deafness.
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Hearing aids are an effective form of treatment for what kind of deafness?
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Conductive deafness.
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Where do CN VIII fibers leave the cochlea? Where are their cell bodies?
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*at the basal turn
*in the spiral ganglia |
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What fluids are contained in the scali vestibuli, tympani and media?
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*scali tympani and vestibuli: perilymph
*scali media: endolymph |
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What separates the scali media from the scali tympani? What is located on this structure?
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*the basilar membrane
*the organ of Corti |
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Describe the arrangement of hair cells on the organ of Corti.
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A single row of 4,000 inner hair cells and three rows of 12,000 outer hair cells, all of which extend the length of the cochlea.
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What separates the end of the scali vestibuli with the beginning of the scali tympani?
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Helicotrema
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After a wave of pressure hits the scali tympani, how is it then detected?
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As the wave passes through the scali tympani it causes the basilar membrane to vibrate. The differential movement of the basilar membrane and the tectorial membrane causes a shearing motion on the hair cells which causes depolarization.
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What is the shape of the basilar membrane unrolled? Describe the tonotropic organization of the membrane.
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*trapezoidal, narrowest at the base and widest at the apex
*each portion is most responsive to vibration at a certain frequency - the apex to low frequency and the base to high frequency |
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Describe the synapses formed by the inner hair cells and those formed by outer hair cells.
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*each inner hair cell synapses with ~10 afferent nerve fibers; this is a divergent arrangement
*each outer hair cell is one of ten such cells to synapse with a single efferent fiber; this is a convergent arrangement |
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How does the tonotropic organization of the basilar membrane affect the sensitivity of the inner hair cells?
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Because of the tonotropic organization of the basilar membrane, each hair cell is maximally responsive to vibrations at a certain frequency (as determined by its position).
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What are otoacoustic emmissions? What is thought to be their purpose?
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They are sounds that are generated by efferent stimulation of the outer hair cells. They are thought to add 30dB to the threshold of hearing and thus sharpen frequency discrimination.
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How are different sounds coded for? What does "critical frequency" mean in this context?
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With a labeled line system: because each afferent fiber is associated with a single hair cell, activity on this nerve signals sound at the frequency of that hair cell. This is the "critical frequency" of that nerve fiber.
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Why are afferent fibers unable to fire with each vibration of a high frequency sound?
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The refractory period of the nerve prevents firing above a certain pace.
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Cochlear implants are an effective treatment for what kind of deafness? Why is this possible?
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*sensorineural deafness
*typically the hair cells are defective but the nerve fibers are fully functional; also the tonotropic organization of the nerve makes it possible |
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Describe briefly how cochlear implants work.
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An external device receives soound and converts it to an electrical signal. This signal is passed through a multi-array electrode that directly stimulates the cochlear fibers of CN VIII. The tonotropic organization of the fibers makes this possible.
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