Figure 9.6. The displacement of the model organ of Corti during sound stimulation at 30 kHz, at one instant in time near the position of the response peak using the normal set of parameters. The viewing angle is different from that in Figure 9.4. Here we are looking at the organ from behind the pillar cells. Scale varies in the figure, with only a 1.5-mm length of the model shown in the vicinity of the response peak, and many of the rows of cells have been removed to aid clarity (there are actually 1000 cells present in this region of the model). At different positions the outer hair cells can be seen to be lengthening and contracting, thereby modifying the displacement pattern of the basilar membrane. The bottom of each outer hair cell moves more than the top, indicating that the basilar membrane is moving considerably more than the tectorial membrane. The length of each Deiters' and pillar cell is constant throughout the model, due to their high axial stiffnesses. Looking in detail at animations of motion within the organ of Corti from all possible viewpoints gives us a deeper understanding of the operation of the cochlear amplifier.
behaviour of the cochlear model suggests that behaviour at organ level is impossible to predict from that of individual cells in isolation. This reinforces the view that finite-element models can provide insights into the operation of biological organs that are impossible to obtain any other way.
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