Hair cells in the cochlea are stimulated by what action?

The stimulation of hair cells in the cochlea primarily occurs through the shearing action. When sound waves enter the cochlea, they create movement in the fluid-filled spaces. This movement causes the basilar membrane to vibrate, which in turn causes the stereocilia (tiny hair-like projections) on the hair cells to bend against the tectorial membrane. The bending of these stereocilia generates an electrochemical signal that is transmitted to auditory nerve fibers, leading to the perception of sound.

While pressure changes and vibrational movements are involved in the overall process of hearing, it is the specific shearing action that directly stimulates the hair cells. Electrical signals, on the other hand, are a result of the stimulation but do not involve the direct mechanical action required to stimulate the hair cells initially. Thus, understanding the role of shearing action is critical in the context of how sound is transduced into neural signals for auditory perception.