inner ear
Summary
The inner ear is the fluid-filled part of the ear that holds the cochlea, where hair cells transduce sound vibrations into neural signals, and the vestibular system, which senses balance and head position. Testable point: transduction happens here, not in the middle ear.
Detail
Meaning: The inner ear has two functional parts: the cochlea for hearing and the vestibular system (semicircular canals, utricle, saccule) for balance. The stapes pushes on the oval window, setting up pressure waves in the cochlear fluid. These move the basilar membrane and bend hair cells in the organ of Corti, which is where mechanical energy becomes a neural signal. The auditory nerve carries it to the brain. The semicircular canals detect rotation of the head; the utricle and saccule detect linear acceleration and head tilt.
On the MCAT: Expect questions that trace the path of sound: pinna, ear canal, eardrum, ossicles (malleus, incus, stapes), oval window, cochlea, hair cells, auditory nerve. Pitch is explained by place theory (different frequencies peak at different spots on the basilar membrane, high pitches near the base and low pitches near the apex) and by frequency theory (firing rate follows the sound frequency). Accounts often combine both. Damage to hair cells gives sensorineural hearing loss; trouble with the eardrum or ossicles gives conductive loss. Dizziness after spinning is a vestibular example: the fluid keeps moving after the head stops.
Common confusion: Students put the eardrum and ossicles in the inner ear. They belong to the middle ear and only pass on and amplify vibration. Transduction occurs at the hair cells of the cochlea.
Sources
- Psychology (Myers)
- Psychology (Schacter, Gilbert, Wegner)
- Sensation and Perception (Wolfe et al.)
Written for the MCAT and checked before it was published. For study reference only. Spotted an error? Let us know.