Cochlear Mechanics Flashcards
In what direction does a rarefaction deflect the basilar membrane?
Upward
In what direction does a rarefaction open the ion channels at the end of the stereocilia?
Laterally
Tip links do what for stereocilia?
Tip links course from the shaft of one stereocilium to the tip of the shorter stereocilium in the next shorter row. As the stereocilia is deflected laterally, tension increases in the tip-link. The tension pulls open the gated ion channels located near the tip of the cilia.
Why does the traveling wave goes from base to apex?
The traveling wave will move from stiffness dominated area to mass dominated areas. Any system that has differential stiffness and mass will make the traveling wave go from high frequencies to low. Thus, the traveling wave will move from base to apex.
The tuning on the basilar membrane is improved by what?
Tuning on the basilar membrane is improved by the cochlear amplifier, which is initiated by the outer hair cells, particularly at lower intensities.
How does the basilar membrane tuning of a zombie compare to an alive person?
Alive individuals will demonstrate sharp tuning curves. Zombies will have broader tuning curves. Zombies are the living dead, which means that they will not have a cochlear amplifier, which is responsible for providing more amplitude to signals at low and medium intensities. The amplifier, which is due to outer hair cell motion, sharpens the tuning of the basilar membrane.
How does the sensitivity of a zombie compare to an alive person?
Alive individuals will have greater sensitivity to pitch and vocal contours. In the case of the zombies, they will have the poorest frequency sensitivity. Due to this, they are not able to distinguish voice pitch and understand prosodic contours.
How long does the traveling wave take to go from base to apex in a human?
10 ms
How does the tuning at the basilar membrane change with level?
As the input level of the stimulus increases, the tuning of the basilar membrane becomes broader.
What are on the axes of a tuning curve?
The X axis of a tuning curve is frequency (Hz) and the Y axis is intensity in dB SPL.
What frequencies show linear basilar membrane input-output functions?
Frequencies that are off-frequency from the characteristic frequency.
Why were von Bekesy’s original Nobel prize winning measurement questioned?
von Bekesy conducted his experiments on cadavers, which proved to be problematic if tuning curves are metabolic dependent. The cochleae of the cadavers were also damaged. The tuning curves that von Bekesy measured were too broad to explain the frequency selectivity. Other experiments with measurements at lower intensities and undamaged cochlea using the Mossbauer technique indicate better tuning.
How does the tuning curve of a hearing-impaired person compare to a typical hearing person?
Tuning curves of a hearing aid person are broader than a typical hearing person. An individual with hearing loss has a threshold at a higher intensity level. The greater intensity needed to reach threshold results in a much larger and broader basiliar membrane displacement, resulting in broader tuning curves.
Does the amplitude of the traveling wave grow or diminish as it travels down the cochlear duct? Why?
The amplitude of the traveling wave grows as it travels down the cochlear duct. This is due to the physical properties of the basilar membrane. The base of the basilar membrane responds to high frequencies and is stiffness limited whereas at the apex, the basilar membrane responds to low frequencies and is mass limited. Any system with differential stiffness and mass will make the traveling wave go from stiffness dominated to mass dominated. The basilar membrane is less stiff at the apex, so the wave is able to grow more until it reaches the resonant frequency and then it dissipates.
After reaching the resonance point, how fast the traveling wave dissipate? Why?
Dissipates quickly after reaching the resonance point and arriving in the mass dominated area of the basilar membrane.
