Human auditory system. Computer artwork showing the main areas involved in hearing and the perception of sounds. The outer ear (ears) collects sounds, which are amplified by the middle ear and then passed into the inner ear (cochlea, spirals, bottom) on each side of the head. The cochlea consists of liquid-filled hollow channels embedded in the temporal bone that have a lining (organ of Corti) studded with sensory hair cells. When stimulated by sound waves the hairs trigger nerve impulses that transmit the sound information to the brain. These impulses travel from each ear through the cranial nerves (dotted lines) to the brain stem (centre) and then to the area of the temporal lobe cortex associated with sound (red-blue, upper left and right), where they are interpreted.