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24 Cards in this Set

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An increase of 1 dB is equivalent to what kind of increase in sound pressure?
Each dB increase means a ten-fold increase in sound pressure.
What determines the pitch of sound?
Its frequency.
What frequencies of sound are audible to humans?
20-20,000 Hz
At what frequency do vowels occur? Consonants? How does this explain a loss of the ability to differentiate consonants as seen in presbyacusis?
*vowels - low frequency
*consonants - high frequency
*high frequency discrimination is one of the first things to go in presbyacusis
What is a spectrograph? How can the fundamental frequency of a sound be recognized on one?
*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
What is one of the unique functions of the pinna?
It helps to determine vertical elevation of sound, one of the few structures to do so.
What is the essential function of the middle ear?
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.
What are the two middle ear muscles and where do they insert? What is their function?
*stapedius - stapes
*tensor tympani - malleus
*dampen vibrations to prevent damage
What is otosclerosis?
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.
Hearing aids are an effective form of treatment for what kind of deafness?
Conductive deafness.
Where do CN VIII fibers leave the cochlea? Where are their cell bodies?
*at the basal turn
*in the spiral ganglia
What fluids are contained in the scali vestibuli, tympani and media?
*scali tympani and vestibuli: perilymph
*scali media: endolymph
What separates the scali media from the scali tympani? What is located on this structure?
*the basilar membrane
*the organ of Corti
Describe the arrangement of hair cells on the organ of Corti.
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.
What separates the end of the scali vestibuli with the beginning of the scali tympani?
Helicotrema
After a wave of pressure hits the scali tympani, how is it then detected?
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.
What is the shape of the basilar membrane unrolled? Describe the tonotropic organization of the membrane.
*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
Describe the synapses formed by the inner hair cells and those formed by outer hair cells.
*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
How does the tonotropic organization of the basilar membrane affect the sensitivity of the inner hair cells?
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).
What are otoacoustic emmissions? What is thought to be their purpose?
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.
How are different sounds coded for? What does "critical frequency" mean in this context?
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.
Why are afferent fibers unable to fire with each vibration of a high frequency sound?
The refractory period of the nerve prevents firing above a certain pace.
Cochlear implants are an effective treatment for what kind of deafness? Why is this possible?
*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
Describe briefly how cochlear implants work.
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.