Power Efficiency of Outer Hair Cell Somatic Electromotility
Figure 5
Axial velocity and isometric force vs. frequency.
A) The zero-load velocity gain and B) phase are shown as functions of frequency for an 80 µm long OHC. Symbols replot data from by Frank et al. [48] (nm/s somatic velocity per mV extracellular microchamber voltage), and solid black curves provide the current model predictions, also in the microchamber configuration. The * denotes the OHC displacement corner frequency observed under microchamber conditions, which increases in value for shorter cells. Also shown are model projections for physiological hair bundle displacements (dotted, nm/s somatic velocity per nm of hair bundle displacement). The series of curves (blue dotted) show predictions for various rates of fast MET adaptation associated with the MET adaptation time constant (tT). Note that MET adaptation is predicted to introduce a broad-band phase roll-off and result in OHC velocity that increases with bundle displacement frequencies below 1/τT and becomes relatively flat for frequencies above 1/τT. C) Isometric force generated by the same cell in the microchamber configuration (symbols) is predicted by the same model (solid black curve). Note the corner frequency is much higher under isometric force conditions due to the restriction on cell movement.