Force from an outer hair cell

The outer hair cell (OHC) is partially sucked into a glass capillary. The transmembrane potential of the cell is changed by applying a voltage (U_SP) to the solution in the capillary. The changes of potential are U₁ and U₂ for the portions of membrane, respectively, outside and inside the capillary. The somatic electromechanical force produced by the excluded section of cell is determined by placing the reverse side of an atomic force lever (AFL) against the apical surface of the cell and using a laser Doppler vibrometer (LDV) to measure the velocity (V_AFL) of the lever in response to the applied voltage. The force is then calculated from V_AFL, and the mechanical impedance of the lever. © 2005 A. W. Gummer. Picture by Dr. G. Frank.