The basilar membrane is surrounded by a larger and complicated structure called the organ of Corti, which additionally contains mechanoreceptors that are similar to those shown in Section 8.2. See Figure 11.6. The mechanoreceptors convert displacements of hairs into neural impulses. The hairs are displaced as the basilar membrane vibrates because the ends of some are attached to the tectorial membrane. The relative motions of the basilar and tectorial membranes causes a shearing action that moves the hairs. Each ear contains around 20,000 mechanoreceptors, which is considerably less than the million photoreceptors in the eye.