Figure 7.

Drawing of outer hair cells showing the effect of different internal pressures. The outer hair cell is divided in three parts. The top part is capped with a flat plate into which the stereocilia are inserted. The base of the cell is hemispheric. It contains the cell nucleus (round ball) and synaptic structures (not shown) for communicating with the central nervous system. The middle part of the cell is cylindrical in shape. The shape of the outer hair cell is maintained by a pressurized fluid core that pushes against an elastic wall. The wall is reinforced by additional layers of cytoskeletal material and membranes (shown in drawing by concentric cylinders). If the cell is at a normal pressure as on the left it will shorten and become fatter (middle) when there is an increase in intracellular fluid. When fluid is lost the cell elongates and the sides of the cell collapse (right) from the loss of pressure.