Other sensory systems

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Other sensory systems
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The auditory system
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Middle ear
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Auditory processing

• Sound waves
• Variations in air pressure
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• 1. Sound wave moves the eardrum
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• 2. Eardrum moves small bones in the middle ear
• 3. Small bones (ossicles) play against the
  membrane at the oval window (hole in skull)
• 4. This moves fluid in the inner ear, in the
  cochlea
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• 5. Motion in this fluid will be picked up by
  auditory receptor cells (hair cells)

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• Sound waves ripple through Basilar
• membrane
• The organ of Corti, with hair cells, moves along
• but the roof doesnt move (tectorial membrane
  stays put)
• This causes something like friction between
• hair cells and tectorial membrane

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Hair cells

• hair cells have about 100 hairy-looking cilia
• on these cilia there are
• mechanically gated potassium channels
• moving in one way opens the channels
• Influx of potassium
• Depolarizes the hair cell
• Unusual
• Due to high concentration of potassium in the
  fluid in the cochlea
• moving in another way closes the channels
• Hyperpolarizes the hair cell