hearing: how do we hear?. our essential questions what are the major parts of the ear? how does the...
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Our Essential Questions
• What are the major parts of the ear?
• How does the ear translate sound into neural impulses?
Pitch
• A sound’s highness or lowness
• Dependent on the frequency of the sound wave– the more “waves per second” the higher the
frequency or pitch
• Measured as hertz (Hz)
Hertz (Hz)
• Measure of the number of sound wave peaks per second; measures frequency
• Determines the pitch of the sound
• Human hearing: 20 Hz - 20,000 Hz
What pitch can you hear?
http://journal.plasticmind.com/ears/mosquito-tone-or-how-to-tell-youre-a-youngun/
Divisions of the Ear
• Ear’s structure can be divided into:
–The outer ear
–The middle ear
–The inner ear
Break It Down
• Sound waves are collected in the outer ear, amplified in the middle ear, and transduced, in the inner ear.
Parts of the Outer Ear – Pinna
•The visible part of the outer ear.•collects sound and directs it to auditory canal
• The opening, tunnel that sound waves travel through
• Ends at the eardrum
Parts of the Outer Ear – Auditory Canal
Parts of the Middle Ear - Eardrum• AKA tympanic membrane• Thin membrane that vibrates when
sound waves reach it• Transfers sound vibration from the
air to the tiny bones of the middle ear
• Damage?
Parts of the Middle Ear - Ossicles
• 3 tiny bones that transfer sound waves from the eardrum to the cochlea
• Hammer, anvil and stirrup– Fun fact: the stirrup is the smallest
bone in the human body – only .25 cm
Parts of the Inner Ear - Oval Window
• Intersection of the middle ear with the inner ear
• Touches the stirrup • As the oval window vibrates, the
fluid in the cochlea vibrates• From eardrum oval window,
sound is amplified 20 times
Parts of the Inner Ear - Cochlea
• A hearing organ where sound waves are changed into neural impulses (transduction)
• The major organ of hearing• Filled with fluid; a snail shaped
body tube
Parts of the Inner Ear - Hair Cells• The receptor cells …what do they do?
• Transduction!
Parts of the Inner Ear - Auditory Nerve
• carries sound information from the ears to the brain
• Like the optic nerve
Hearing - Review
• Sound is collected by pinna• Goes through the ear canal to the
eardrum• Eardrum changes sound vibrations• Vibrations go from middle ear
inner ear via oval window
Hearing - Review
• Here vibrations neural impulses so that the brain can read / interpret the sound
• What are the receptors cells for hearing?
Problems with hearing• Conduction deafness (middle
ear damage)
• Nerve deafness (hair cell or auditory nerve damage)
Problems with hearing
•http://www.youtube.com/watch?v=lioNIbtFxSY&feature=related
• Cochlear Implants:
• http://www.youtube.com/watch?v=4Avc3nNFxIA&feature=related
Hair Cell Loss
• Read the article “How the iPod and other audio devices are destroying your ears”
• Answer the review questions at the end
Localization of Sound
• Locating where sound is originating from
• Done through two cues:
–Which ear hears the sound first?
–Which ear hears the sound louder?
YOU Break It Down This Time
• Sound waves are ______ in the outer ear, _______ in the middle ear, and ________, in the inner ear.
Vestibular Sense• body orientation and balance
• Receptor cells: semicircular canals, hair cells in inner ear
• Parietal lobes
• Motion sickness = overstimulation
Let’s Process
• Get a piece of paper• Trace the ear• Label as much as you can by your self
– 60 seconds• Get with a partner – fill in the rest • Together, briefly describe how sound
is changed into neural impulses
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