Final answer:
The basilar membrane's movements during sound wave transduction bend hair cells, which release neurotransmitters and generate action potentials for the auditory nerve, allowing the brain to process sound frequencies.
Step-by-step explanation:
The up and down motion of the basilar membrane activates the hair cells by causing them to bend against the tectorial membrane. When sound waves enter the ear, they are translated into fluid waves within the cochlea. These fluid waves cause the basilar membrane to move, which in turn bends the hair cells' stereocilia that are in contact with the overlying tectorial membrane.
Action potentials are generated when the bending of these hair cells leads to the release of excitatory neurotransmitters at synapses with sensory neurons. This electrical signal is then carried to the brain via the cochlear branch of the vestibulocochlear cranial nerve. The cochlea can encode sounds between 20 Hz and 20,000 Hz, separating these frequencies along its length, much like a prism separates light into its component colors.