Final answer:
Hair cells have tonic neurotransmitter release and deflection towards the tallest member of their stereocilia array depolarizes the hair cell membrane, while deflection away closes the ion channels.
Step-by-step explanation:
Hair cells in the cochlea have tonic neurotransmitter release, meaning they release neurotransmitters continuously even without deflection. When the stereocilia of the hair cells bend toward the tallest member of their array, tension in the protein tethers opens ion channels in the hair cell membrane, depolarizing the hair cell membrane and triggering nerve impulses. On the other hand, when the stereocilia bend away from the tallest member of their array, the tension on the tethers slackens and the ion channels close.