What part of the ear is a coiled, bony, fluid-filled tube that converts sound waves into nerve impulses?

The cochlea is the part of the ear that is a coiled, bony, fluid-filled tube responsible for converting sound waves into nerve impulses. Inside the cochlea, sound waves cause the fluid to move, creating waves that stimulate hair cells located in the basilar membrane. These hair cells then convert the mechanical energy of the sound into electrical signals that are transmitted to the auditory nerve and ultimately interpreted by the brain as sound.

This function is critical because it is the primary mechanism through which auditory information is processed in the body. The cochlea's unique spiral structure allows for the organization of sounds based on their frequency, meaning different parts of the cochlea are sensitive to different pitches. This ability to translate physical sound waves into meaningful neural signals is essential for hearing.

Other parts of the ear have specific roles, such as the middle ear, which amplifies sound vibrations, the auditory canal, which directs sound waves to the eardrum, and the semicircular canals, which are involved in balance rather than hearing. Thus, the cochlea plays a key role in the auditory system, making it the correct answer.