The Ear Biology 30

The Ear – label your diagram

Outer Ear: Pinna: The external flap of the ear. Funnels sound into the auditory canal. Auditory Canal: Directs sound toward the tympanic membrane towards the ear drum Has modified sweat glands (Ceruminous Glands) that secretes wax to protect from foreign material (keeps ear moist; trap dirt, debris, etc)  

Middle Ear: Tympanic Membrane Ossicles Eustachian Tube Turns sound waves into a vibration also called the “ear drum”   Ossicles Three ossicles: Malleus (Hammer), Incus (Anvil), Stapes (Stirrup) Amplifies and transfers the vibrations from the tympanic membrane to the oval window Eustachian Tube Connects middle ear to the back of the throat (pharynx) Equalizes air pressure in the middle ear and allows proper movement of the tympanic membrane

Inner Ear - Hearing: Cochlea - coiled structure of the inner ear, responds to various sound waves and converts them to nerve impulses Oval Window – receives vibrations from the ossicles (specifically stapes) Round Window – absorbs the sound wave Organ of Corti – primary sound receptor in the cochlea (hair cells in cochlea and neurons they’re attached to)   Nerve impulse travels from the auditory nerve to the temporal lobe and are interpreted as sound.

Organ of Corti Is a ridge of cells that runs along the basilar membrane. The top of the organ of Corti meets the tectorial membrane

Hearing Animation http://www.science.nelson.com/ABbio20- 30/student/protect/webactivities/unit30Ach14.html#14.2 Username: nelsonbio_student Password: nelsonbio_onlinelearning

Inner Ear – Balance: Semicircular Canals Vestibule Arranged in all three dimensions of space Base of each canal has hair cells with cilia Provide a sense of balance (dynamic balance – 3D motion)   Vestibule A chamber between the semicircular canals and cochlea Contain two membrane sacs: Utricle and Saccule static balance, when you move your head Both contain hair cells with cilia protruding into a gelatinous material that has otoliths (calcium carbonate particles)

http://www.nelson.com/ABbio20-30/student/protect/animations/unit30Ach14.html#14.2

Balance – Semicircular Canal Fluid inside the canals flows in the direction of motion. Small jelly-hairs bend in the direction of the fluid flow Nerves fire and the brain interprets motion & responds for balance

Balance Dynamic Equilibrium – required when the body is moving Fluid in the semicircular canals causes bending of the hair cells which generates a nerve impulse which travel to the temporal lobe of the brain Continuous movement causes motion sickness Static Equilibrium – required when the head or body move horizontally or vertically Otoliths in vestibule of utricle and saccule are displace by gravity The otoliths come in contact with the hair cells bending them which generates a nerve impulse which travels to the temporal lobe of the brain

Hearing Summary: Sound waves are vibrating molecules Sound waves cause the tympanic membrane to vibrate slightly Malleusincus stapes relay vibration to the oval window with a 20-fold increase in pressure Vibration at oval window are converted into compression waves of the inner ear The compression wave travels through the vestibular canal and then the tympanic canal This causes the basilar membrane in the cochlear canal to move up and down also moving the Organ of Corti Cilia in the Organ of Corti rub against the tectorial membrane initiating a nerve impulse The vibration is absorbed by the round window at the end of the cochlea The nerve impulse travels along the auditory nerve to the temporal lobe Long wide hair responds to low pitch sound and short narrow hair respond to high pitch sound

STS – Hearing technology Hearing aids Bed vibrator: clock & fire alarms TTY Phone Closed caption TV Pager/Vibrator: doorbell, contacts