When a sound is presented, the endocochlear potential changes either positive or negative in the endolymph, depending on the stimulus.
With the movement of the basilar membrane, a shear force is created and a small potential is generated due to a difference in potential between the endolymph (scala media, +80 mV) and the perilymph (vestibular and tympanic ducts, 0 mV).
An acoustic stimulus produces a simultaneous change in conductance at the membrane of the receptor cell.
Because there is a steep gradient (150 mV), changes in membrane conductance are accompanied by rapid influx and efflux of ions which in turn produce the receptor potential.
The receptor potential for each hair cell causes a release of neurotransmitters at its basal pole, which elicits excitation of the afferent nerve fibres.