The Human Ear

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The Human Ear

• Definition the organ humans use to detect sound.

http//www.a3bs.com/3d_models.html
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The human ear is divided into three sections.
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Each part of the ear serves a specific purpose in
the task of detecting and interpreting sound.
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The Outer Ear

• Picture a satellite dish that collects radio
  waves.
• The outer ear is similar!
• The curved formation on the outside ( the pinna)
  helps funnel sound down the ear canal to the
  eardrum.

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The Middle Ear

• The middle ear transfers the energy of a sound
  wave by vibrating the three bones found there.

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Bones of the Middle Ear

• These are the smallest bones in your body!
• Together, theyre about the size of an orange
  seed.

Hammer
Anvil
Eardrum
Stirrup
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The Stirrup (or stapes)
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How Sound Travels in the Middle Ear

• When sound waves reach the middle ear, they cause
  the eardrum to vibrate.
• This vibration then causes the three bones to
  vibrate.
• These vibrations are transformed into
  longitudinal/pressure waves in the middle ear.

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The Inner Ear

• Two main parts
• Cochlea
• Auditory Nerve

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The Cochlea

• Coiled like a snail shell
• Contains approximately 300,000 hair cells
• Is filled with fluid, through which sound can
  travel easily.

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Cochlear Hair Cells

• These tiny hairs bend because of the vibrations
  caused by the sound waves.

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Cochlear Hair Cells in Action
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The Auditory Nerve

• The tiny hair cells of the cochlea are set in
  motion by vibrations
• The vibrations stimulate tiny nerve cells.
• The nerve cells then send signals along the
  auditory nerve to the brain.

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A sound is not actually heard until the brain
receives and processes these signals.
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Lets start at the very beginning

• http//www.youtube.com/watch?vCSO765hyxrc

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• Put the following steps in order
• The stirrup moves back and forth, creating
  pressure waves in the cochlea.
• The bones of the middle ear (hammer, anvil,
  stirrup) vibrate.
• Hair cells send an electrical impulse through the
  auditory nerve.
• The outer part of the ear (the pinna) "catches"
  the sound waves.
• Sound waves vibrate the eardrum
• The brain receives an electrical impulse and
  interprets it as sound.
• Tiny hair cells in the cochlea move as the waves
  pass.
• The sound waves travel into the ear canal.

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