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Ear: Sound & Balance. Sensory System. 3 Parts : Outer – Middle - Inner. Outer Ear: Auricle. Called the Pinna Fx : Collects sound waves Visible part of the ear, outside the head. Outer Ear: External Auditory Canal. Extends from Pinna to eardrum Fx: Transmits sound waves.
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Ear: Sound & Balance Sensory System
Outer Ear: Auricle • Called the Pinna • Fx: Collects sound waves • Visible part of the ear, outside the head
Outer Ear: External Auditory Canal • Extends from Pinna to eardrum • Fx: Transmits sound waves
Outer Ear: External Auditory Canal • Produces Cerumen (earwax) • Fx: Traps foreign bodies
Middle Ear: • Air-filled • Converts sound waves to mechanical energy • Amplifies it • Conducts to next chamber
Components: • Tympanic membrane – Eardrum • Vibrates • Sound to Mechanical Energy
Otitis Media • Inflammation of the middle ear
Components: • Ossicles – 3 bones • Malleus (Hammer) • Incus (Anvil) • Stapes (Stirrup) • Fx: Mechanical vibration
Middle Ear: • Oval window - Tranfers mechanical vibration from middle ear to inner ear
View of OVAL WINDOW Oval Window
Eustachian Tube Fx: • Adjusts pressures between middle ear & outside • Drains middle ear
Eustachian Canal • Normally closed • Swallowing & yawning open it • Tympanic membrane will not vibrate well if pressures not equal
Eustachian Canal • If fail to open, increased pressure (pain) and infections
Requires Ear Tubes – drain the excess fluid & prevent infection
Inner Ear • Bony Chambers (fluid-filled) • Vestibule • Semicircular Canals • Cochlea
Inner Ear Bony Labyrinth • Fluid-filled = Perilymph • Membranous sac is suspended in the periliymph = Membranous labyrinth
Inner Ear Membranous Labyrinth • Sac contains thick fluid = Endolymph
Hearing and the Inner Ear - Cochlea • Snail-like shape • Membranous sac contains organ of Corti
Cochlear Ducts Membranous labyrinth Perilymph Endolymph Organ of Corti
Organ of Corti • Contains specialized hearing receptors or hair cells • Embedded in basilar membrane
Organ of Corti • Hair cells covered by gel membrane (Tectorial membrane) • Corti converts mechanical energy into electrochemical energy
Hearing Process • Ossicles vibrate oval window • Sets the fluids into motion (pressure waves)
Hearing Process • Vibrate basilar membrane • Hair cells rub tectorial membrane (bent)
Hearing Process • Hair cells transmit impulse to cochlear nerve • Interpretation of sound in temporal lobe
Sound Energy to Hearing Interpretation Sound Energy Mechanical Energy Mechanical Electrochemical
Balance: Static Equilibrium • Position of head when not moving (which way is up) • Membranous sacs in vestibule contain maculae
Maculae Physiology • As head moves, otoliths roll in response to gravity • Pulls on gel and bends hairs in receptors
Maculae Physiology • Hair cells send impulse via vestibular nerve • Signal to cerebellum for interpretation
Balance: Dynamic Equilibrium • Rotation of head or movement is detected • Membranous semicircular canals filled with endolymph
Crista Ampullaris • Membranous semicircular canals contain crista ampullaris
Crista Ampullaris • Contains receptor cells (w/ hairs) embedded in cupula (gel-like cap)
Ampullaris Physiology • When head moves, endolymph lags behind • Cupula drags against endolymph current and bends hairs
Ampullaris Physiology • Stimulates hair cells to send impulse • Vestibular nerve sends impulse to cerebellum