The Ear and Hearing

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The Ear and Hearing Ex. 30 pg. 213 Cross out the
facial nerve!!!!
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Lab Objectives

• ID the major structures of the ear (see lab
  manual for list)
• Describe their functions
• Trace the path of sound from outside the ear to
  the brain
• Conduct and understand hearing tests

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Robert Bárány

• Austrian physiologist
• Studied balance as a function of the inner ear
• 1914 Nobel Prize
• Bárány Chair
• Spins subject around while staying true to a
  vertical axis
• Used to show pilots not to trust the vestibular
  system

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Nystagmus

• Involuntary eye movements
• Fluid moves through semicircular canals while
  spinning
• When subject stops, the fluid in the ear keeps
  moving because of inertia
• The eyes try to focus but cant because the
  semicirc. canals are still saying Hey, we are
  still spinning!. Eyes try to track but, cant.

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Deafness

• 2 types
• Nerve- Nerves are damaged, they dont carry
  impulses to the brain
• Fixed by cochlear implant
• Conductive- Something is wrong with the parts
  that transfer vibrations to the cochlea
• Can surgically bypass ossicles and go right to
  the cochlea

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Hearing tests

• Auditory Acuity Test
• Hold ticking clock close to ear
• Pull away from ear slowly
• Measure the distance in which the subject can no
  longer hear the clock
• Sound Localization
• While subjects eyes are closed, hold watch
  within vicinity of head
• Subject must point out location of clock
• How accurate where they?

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Hearing tests contd

• Rinne test- test for conduction deafness
• Strike tuning fork on your hand ONLY
• Place end of tf on subjects mastoid process,
  behind the ear with prongs pointed down
• If no sound is heard, nerve deafness could exist
• Once subject can no longer hear the tf on the
  mastoid process, move to right next to the ear
• Subject should hear tf again
• If no sound is hear, conductive deafness could be
  the reason

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Hearing tests contd

• Weber test- helps distinguish between conductive
  and sensory deafness
• Strike tuning fork on hand ONLY
• Put it in middle of forehead
• Is it louder in one ear or the other or equally
  loud in both ears?
• The ear that it is louder in could indicate
  conductive
• The bone conducts the sound to the cochlea while
  outside noise it not thus making it louder

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Questions or comments