Hearing and Equilibrium

Outer Ear Auricle– “ear” shell- shaped, surrounds external opening to auditory canal Auditory canal – channel through temporal bone Tympanic membrane- eardrum; vibrates when stimulated by sound waves.

Middle Ear Air filled cavity called tympanic cavity (middle ear cavity) From eardrum to bony wall with oval and round window Auditory tube runs down connecting ear to throat

Functional parts of middle ear Ossicles- 3 small bones Hammer (malleus), Anvil (incus), and Stirrup (stapes) Eardrum vibrates hammer, which moves anvil, which then moves stirrup, opening oval window. Oval window moves fluids inside inner ear

Inner Ear Located deep inside temporal bone (behind eye socket) Contains 3 major divisions

Anatomy of Inner ear Cochlea- contains auditory (cochlear) nerve, which transmits sound impulses; hair cells receive vibrations from oval window, indicating sound Different pitches affect different areas of cochlea

Semicircular canal Located in inner ear Responsible for maintaining balance/equilibrium Otoliths float inside canal Hair cells recognize when the otolith moves, alerting the body of its positioning when static

Dynamic equilibrium Position while moving is determined in semicircular canal Triggered when spinning, moving on a boat, etc. Causes dizziness and motion sickness

Types of Deafness Conduction – problem in conduction of sound vibrations; hearing aids can help by transmitting sound to/through bone Sensorineural – degeneration or damage to nerves which carry impulse.