1. Hearing and Equilibrium
Receptors convert sound vibrations into electrical signals 1000 times faster that photoreceptors can respond to light.
Our ears also contain receptors for equilibrium (balance)

2. Structure of the ear 3 major regions
Outer ear – collects sound waves and channels them inward
Middle ear – conveys sound vibrations to the oval window
Inner ear – houses the receptors for hearing and equilibrium

3. Outer ear
Auricle – the part of the ear you see, collects sound waves and directs them to the external auditory canal (tube that directs sound waves toward the eardrum).
External auditory canal – contains a few hairs and ceruminous glands which secrete cerumen (earwax). The hairs and cerumen help prevent foreign objects from entering the ear.

4. Outer ear
Eardrum – also called the tympanic membrane – thin partition between external auditory canal and the middle ear.
Sound waves cause the eardrum to vibrate.
Tearing of the tympanic membrane, due to trauma or infection, is called perforated eardrum

5. Middle ear
Is small air filled cavity between the eardrum and inner ear
Eustachian tube connects the middle ear with the upper part of the throat. This tube equalizes air pressure on both sides of the eardrum. During swallowing and yawning the tube opens and can equalize pressure. This is why chewing gum and yawning helps during a flight on an airplane.

6. Middle ear
Connected to the center of the eardrum is the malleus (hammer). Then the incus (anvil) and then the stapes (stirrup). These bones are collectively called ossicles. The ossicles are responsible for sound conduction and amplification.
These tiny bones cause the oval window to vibrate sending the sound waves into the inner ear.

7. Inner ear
2 areas – 1) outer bony labyrinth and 2) inner membranous labyrinth
Bony labyrinth
includes the cochlea, vestibule (the middle part) and semicircular canals
Semicircular ducts – senses for dynamic equilibrium
Cochlea – receptors for hearing are located here

8. Inner ear
Organ of Corti – is the organ of hearing. It changes vibrations to nerve impulses. The hair cells are located here which are the receptors for auditory sensations.

9. Equilibrium
Static equilibrium – the maintenance of the position of the body (mainly the head) relative to the force of gravity
Dynamic equilibrium – the maintenance of body position (mainly the head) in response to sudden movements such as rotation, acceleration, and deceleration.
Collectively the receptor organs for equilibrium (saccule, utricle and membranous semicircular ducts) are called the vestibular apparatus.

10. Equilibrium
Macula – thickened region of the utricle and the saccule. These are receptors for static equilibrium. The provide sensory info for the position of the head and help maintain appropriate posture and balance. The also are responsible for the sensations you have while riding in an elevator or a car that is speeding up or slowing down.

11. Disorders Tinnitus – ringing, roaring, or clicking in the ears
Deafness
Sensorineural deafness – impairment of hair cells in the cochlea or damage to the cochlear branch of the vestibulocochlear nerve. Caused by exposure to loud noise which destroys the hair cells of the spiral organ
Conduction deafness – impairment of the outer and middle ear mechanisms. Caused by aging, thickening of the eardrum