more cochlear anatomy and physiology Flashcards
what are OAEs
-Generally speaking, OAEs are waves generated
by movement of the basilar membrane and
are measured in the external auditory canal.
-However, with an in-depth understanding of
cochlear anatomy and physiology, OAEs can
be directly related to OHC function.
what is the 1st step of getting OAEs
First, there is a stimulus delivered to the ear. This stimulus invokes movementof the basilar membrane, which in turn causes the OHCs to move, or bedeflected.
what is the 2nd step of OAEs
When the OHCs move, their stereocilia bend in one direction or the other.Ions rush in and rush out, changing the membrane potential within the haircell.
what is the 3rd step of OAEs
The changes in voltage across the plasma membrane lead to OHC length changes (shortening and lengthening), which are called electromotility.
what is the 4th step of OAEs?
The electromotility of the OHCs has a feedback effect on the basilar membrane, causing it to vibrate.
what is thought to be the mechanism that underlies OAES
the electromotility of the OHCs is thought to be the mechanism which underlies OAEs.
because of research, if electromotility is blocked how are OAEs affected?
when the OHC electromotility is blocked, OAEs are absent, which solidifies the relationship between OHC motility and OAEs.
what else happens because of the motility of the OHC?
In addition to vibrating the basilar membrane, the motility of the OHCs causes an amplification of the signal, which is then passed to the IHCs.
what happens once the IHC are stimulated?
the IHCs send a signal to the brain and we then “hear.” The OHC motility allows us to be more sensitive to softer sounds. This is called active processing within the cochlea.
what would happen if we didnt have OHC amplifying?
-Without the amplification provided by the OHCs, the IHCs would only betriggered by relatively loud sounds.
-This is because loud sounds result in larger movements of the basilarmembrane, and the IHCs are stimulated directly with little contribution oramplification from the OHCs. This is called passive processing.
What is a traveling wave and how does it relate?
The traveling wave with stimuli of different frequencies causes maximum disturbance along different lengths of the cochlear partition, known as tonotopicity
how does a traveling wave relate?
-The traveling wave is a result of the pressure differential between the SV and ST, casing the cochlear partition to move either up or down.
-In other words, the traveling wave is an outcome of the pressure difference between the fluid chambers above and below the cochlear partition (the TW does not necessarily travel along the BM)
what happens once the OAE has been generated?
Once the OAE has been generated, the energy still has to travel to the base of the cochlea, out through the middle ear, and into the external ear canal to be measured
what is the traditional view that is typically seen once the stimuli enters the cochlea?
The traditional view has been that if the stimuli enter the cochlea and arrive at their characteristic frequency region via a traveling wave, the OAE must also travel out of the cochlea via a reverse traveling wave
is a reverse traveling wave a viable mode of energy transport in the cochlea?
no
