Final answer:
The Organ of Corti, containing mechanoreceptor hair cells, is anchored to the basilar membrane and is activated by the movement of cochlear fluids, which allows it to transduce sound waves into neural signals.
Step-by-step explanation:
The Organ of Corti is the structure anchored to the basilar membrane within the cochlea that is activated by the movement of the fluids, the endolymph and the perilymph. The vibrations that enter the cochlea through the oval window cause the fluid within the scala vestibuli and scala tympani to move, which in turn causes the basilar membrane to move. This movement varies depending on the frequency of the sound. The Organ of Corti contains mechanoreceptor hair cells that respond to these movements by changing their electrical potential, leading to the transduction of sound waves into neural signals that are interpreted by the brain.