How are sounds converted to nerve impulses?
What we call the “ear” is only the pinna, or visible, external part of the ear. In addition to being a good place to hang earrings or balance pencils, the pinna acts like a funnel to concentrate sounds. After they are guided into the ear, sound waves collide with the eardrum (tympanic membrane), which is like a tight drumhead within the ear canal. The sound waves set the eardrum in motion. This, in turn, causes three small bones called the auditory ossicles to vibrate. The third ossicle is attached to a second membrane, or drumhead, called the oval window. As the oval window moves back and forth, it makes waves in a fluid within the cochlea. The cochlea is really the organ of hearing, since it is here that waves in the fluid are detected by tiny hair cells, which generate nerve impulses to be sent to the brain. 3. How are higher and lower sounds detected? The frequency theoryof hearing states that as pitch rises, nerve impulses of the same frequency are fed into the auditory nerve. Thi
