Anatomy and Physiology / Unit 6: The Nervous System and Senses
6.7 The Ear, Hearing and Equilibrium
Notes
- Outer ear: auricle and ear canal to the eardrum (tympanic membrane). Middle ear: three ossicles (malleus, incus, stapes) amplify vibrations; the eustachian tube equalizes pressure with the throat. Inner ear: the cochlea (hearing) and the vestibule and semicircular canals (balance).
- Pathway of sound: air, eardrum, ossicles, oval window, fluid in the cochlea, hair cells in the organ of Corti, auditory nerve, temporal lobe.
- Higher pitch stimulates hair cells near the base of the cochlea; louder sound makes bigger vibrations.
- Static equilibrium (head position) is sensed in the vestibule; dynamic equilibrium (rotation) in the semicircular canals.
- Conduction deafness involves blocked sound transmission (earwax, ossicle damage); sensorineural deafness involves damage to hair cells or the nerve. Middle ear infection (otitis media) is common in children.
Practice
Which is the correct order of structures through which sound vibrations pass in the ear?
Sound travels eardrum, malleus-incus-stapes, oval window and then fluid in the cochlea.
After spinning rapidly, a child feels dizzy. Which structures detect the rotation?
The semicircular canals sense rotational (dynamic) movement.
A child with an ear infection has trouble hearing because fluid blocks movement of the ossicles. This is:
Blocked sound transmission through the middle ear is conduction deafness.
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