Final answer:
The spiral organ's primary function is to transform sound vibrations into nerve impulses by way of hair cells bending in response to fluid movements in the cochlea, which then send signals to the brain for auditory perception.
Step-by-step explanation:
The function of the spiral organ, also known as the organ of Corti, is to convert sound vibrations into nerve impulses that can be interpreted by the brain as sound. Located in the cochlea of the inner ear, the spiral organ contains hair cells with stereocilia that make contact with the overlying tectorial membrane. When sound waves enter the ear, they cause the eardrum to vibrate, and these vibrations are carried through the ossicles to the oval window, which then transmits the vibrations to the fluid inside the cochlea. The movement of this fluid causes the basilar membrane, where the hair cells are anchored, to move, bending the stereocilia. This bending opens ion channels, leading to the depolarization of the hair cell and initiating a nerve impulse that is sent to the auditory nerve.
The intensity of sound is indicated by the number of hair cells stimulated; the more hair cells stimulated, the higher the perceived volume. The position along the cochlea where the hair cells are stimulated represents different sound frequencies, enabling us to distinguish between high and low pitches. The entire process allows the ear to perform a complex set of mechanisms by which mechanical vibrations in our environment are translated into a rich tapestry of sounds we experience in everyday life.