The Outer Hair Cell: A Mechanoelectrical and Electromechanical Sensor/Actuator

Abstract

The outer hair cell (OHC) is unique to mammals and is required to perceive and discriminate high frequency sounds (> 10kHz). This sensory cell has the remarkable motor ability to convert sound induced receptor potentials into mechanical energy (electromotility). Although the mechanism of electromotility has remained elusive, a systematic review of its characteristics places many constraints on possible models. A sensor-motor ability resides in the outer hair cell's lateral plasma membrane, the outermost layer of an elegant trilaminate lateral wall. The passive biophysical properties of this wall contribute to the robustness of the electromotile response. Analysis and modeling of OHC electromotility is an important step in understanding the putative role of the outer hair cell as the cochlear amplifier. This role requires that OHCs are both sensors and actuators making the cell a self-assembling micro-electro-mechanical system. Electromotility has been observed in the membranes of other cell types, suggesting a universal mechanism. This review will focus on the characteristics and modeling of OHC electromotility.