Overview
How the Ear Converts Sound and Movement into Perception
The ear has three functional regions. The outer ear collects sound, the middle ear transmits and amplifies vibration, and the inner ear converts that vibration into neural signa...
The ear has three functional regions. The outer ear collects sound, the middle ear transmits and amplifies vibration, and the inner ear converts that vibration into neural signals while also detecting head movement. The pinna directs sound into the external auditory canal. At the canal’s medial end, the tympanic membrane vibrates. Those vibrations move the malleus, incus, and stapes across the air-filled middle ear. The stapes transfers energy through the oval window into the fluid-filled cochlea. Within the cochlea, movement of the fluid bends hair cells. The hair cells generate impulses carried by the cochlear branch of cranial nerve VIII. Damage before the cochlea usually creates a conductive problem; damage to the hair cells, cochlear nerve, or central auditory pathways creates a sensorineural problem. The Eustachian tube connects the middle ear with the nasopharynx. It equalizes pressure and permits drainage. In young children, the tube is shorter and more horizontally oriented, so upper-respiratory congestion more readily obstructs it. Poor ventilation then produces negative middle-ear pressure and fluid stasis—the setting in which acute otitis media can develop. The semicircular canals detect...