Post on 25-Feb-2016
description
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 toMechanical
Energy
Perforated Eardrum:
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
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 DuctsPerilymph
Membranous labyrinth
EndolymphOrgan 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