1. 9.6 Hearing and Equilibrium Pages 445-448

2. The Ear Two separate functions: hearing and equilibrium Cilia: tiny hair cells that respond to mechanical stimuli Movement of cilia causes a nerve cell to generate an impulse

3. The Ear Can be divided into 3 sections: 1.The outer ear 2.The middle ear 3.The inner ear

4. The Outer Ear The Pinna External flap that collects and funnels the sound waves from a large area to a canal The Auditory Canal Carries sound to the eardrum (tympanic membrane) and makes earwax that traps, collects, and pushes out foreign invading particles

5. The Middle Ear Eardrum or tympanic membrane – receives sound waves and resonates, causing the ear bones to move 3 small bones: malleus, incus and stapes The malleus receives the vibrations from the eardrum  moves vibration to the incus  moves to the stapes

6. The Middle Ear Ear bones are small and dense. They amplify the vibrations and transfer the mechanical energy efficiently to the oval window The oval window receives sound waves from the ear and transfers it to the fluid in the inner ear

7. Inner Ear Made up of three distinct areas – the vestibule, the semi-lunar canals, and the cochlea The vestibule and semi-lunar canals are involved with balance, while the cochlea is related to hearing The hairs in the cochlea respond to different frequencies ▫Short hairs  high frequency ▫Long hairs  low frequency

8. Eustachian Tube Extends from the middle ear to the mouth and the chambers of the nose It functions to equalize the air pressure on both sides of the eardrum This is the reason why throat infections often lead to ear infections, or vice versa

10. Hearing and Sound Waves push against the eardrum and vibrations are passed to the three bones of the middle ear The bones transfer, amplify, and concentrate the mechanical wave to an oval window The oval window pushes inward, the round window, located immediately below the oval window, moves outward, triggering waves of fluid within the inner ear

11. Hearing and Sound The cochlea receives these movements, the hairs are stimulated, and the mechanical pulse is converted into an electrical signal When the hairs move, the sensory nerves in the basilar membrane are stimulated Auditory signal is then sent to the temporal lobe of the cerebrum via auditory nerves, and the sound is banked

13. Safety Mechanism A Reflex Arc ▫Restrict the movement of the malleus and reduce the intensity of movement ▫Muscle contracts, pulling the stapes away from the oval window  protects the inner ear from powerful vibrations If the sound is too sudden – like a bomb or fire cracker – the protective reflex doesn’t kick in fast enough

14. Equilibrium (Static) Involves movement along one plane Head position  monitored by fluid-filled sacs saccule and utricle which contain cilia in a gelatinous material with otoliths Normal position: otoliths do not move Head tilts: otoliths cause gelatinous material to shift, the hair receptors to bend and the sensory nerve to relay message to brain.

15. Head Erect  Cilia remain erect Head Moves  Cilia move

16. Equilibrium (Dynamic) Provides information about movement Balance is maintained by 3 semicircular canals equipped with a pocked called the ampullae Rotational stimuli causes fluid to move, bending cilia attached to the hair cells in the ampullae Once hair cells bend, information is relayed to the brain