1. The Ears and Hearing

2. Anatomy of the Ear external ear
pinna or auricle – outer, funnel-like structure; collects sound waves traveling through air
external auditory meatus – tube that leads inward through the temporal bone
tympanic membrane (eardrum) – cone-shaped membrane attached to the malleus
reproduces sound waves

4. Anatomy of the Ear (cont)
middle ear
tympanic cavity – air-filled space in temporal bone that contains the auditory ossicles
auditory ossicles: transmit vibrations between eardrum and inner ear
malleus (hammer) – attaches to the eardrum & vibrates in unison
incus (anvil) – passes the vibration on to the stapes
stapes (stirrup) – passes vibration onto fluid within the inner ear

6. Anatomy of the Ear (cont)
inner ear
semicircular canals – function in equilibrium
cochlea – contains receptor cells called hair cells; vibrations in the fluid of the cochlea are picked up by the hair cells
auditory tube (Eustachian tube)
connects middle ear to the throat
conducts air between the tympanic cavity and the outside of the body
helps maintain equal air pressure on both sides of the eardrum

7. Popping of Ears
Explain how the auditory tube is related to your ears “popping” when you experience a change in altitude:
air pressure changes with altitude; so when a person changes altitude, the pressure on the outside of the eardrum changes; this change in air pressure can push the eardrum inward or outward, impairing hearing; when the air pressure difference is great enough, air movement into or out of the auditory tube equalizes the pressure on both sides of the eardrum, and the eardrum moves back to its regular position; this produces a popping sound and restores normal hearing.
That is why you swallow to equalize the pressure inside and outside the ear drum.

9. Physiology of Hearing Steps:
Sound waves enter external auditory meatus.
Eardrum reproduces vibrations from sound wave source.
Auditory ossicles (malleus & incus) amplify and transmit vibrations to end of stapes.
Movement of stapes transmits vibrations to fluid of the inner ear.
Hair cells of inner ear pick up the vibrations in the fluid.
The stimulated hair cells release a neurotransmitter.
The neurotransmitter stimulates the ends of nearby neurons which transmit the sensory impulse along the vestibulocochlear nerve to the auditory cortex of the temporal lobe of the brain.
The auditory complex interprets the sensory impulse.

11. Hearing Loss
conductive deafness – (anatomical deafness) interference with the transmission of vibrations to the inner ear; due to plugging of the external auditory meatus or changes in the eardrum or auditory ossicles
sensorineural deafness (nerve deafness) – damage to the cochlea, auditory nerve, or auditory nerve pathways; can be caused by loud sounds, tumors in the central nervous system, brain damage, or use of certain drugs