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Auditory System (Auditory Disorders (Bilateral Deafness, Unilateral …

- - - - auditory canal
  - - - ossicles - role in the amplification of sound
        
        Malleus (hammer)
        
        Incus (anvil)
        
        Stapes (stirrup)
        
        footplate - bottom portion
        moves in and out
        
        transmits vibration to cochlea
        
        Role
        sound waves move tympanic membrane
        
        ossicles move oval window
        act as levers that amplify the wave to get the needed pressure to push fluid and vibrate cochlear fluid
  - - - oval window
        
        auditory vestibular nerve
      - Cochlea
        3 parallel, fluid filled chambers
        
        Scala vestibulli
        
        Perylimph fluid
        Low K+, High Na+
        
        scala media
        
        endolymph fluid
        High K, low Na
        
        Scala tympani
        
        Perilymph fluid
        
        Difference in two fluids gives APs
        
        Organ of corti
        sits on basilar membrane
        contains auditory receptor cells
        vibrates in response to waves
        wave turned to AP
        
        Tectorial membrane
        hangs over organ of corti
        
        where the tip of the stereo cilia reach
        
        Hair Cells
        receptors but not neurons (only release NTs)
        epithelial cells for transduction of sound into neural signals
        use glu as NTs
        eGlu3 exclusive
        
        have cilia that extend to lamina
        
        Stereocilia
        causes deflection of basilar membrane
        
        Outer Hair cells
        bent back and forth by tectorial membrane
        
        Inner Hair Cells
        bend in response to moving endolymph
        
        Tip Links
        
        2 more items...
        
        Innervation of Hair cells
        
        spiral ganglion provide all auditory info sent to brain
        
        inner hair cell
        single inner hair cell can innervate up to 10 spiral ganglion
        
        outer hair cells
        multiple outer hair cells send info to one spiral ganglion
        
        1 more item...
        
        Uncoiled Cochlea
        wide base, narrow apex
        
        Basal Membrane
        narrow base, wide apex
        
        High Frequency
        vibrates stiff base and dissipates
        
        Low Frequency
        propagates floppy apex
        
        Tonotopic map
        place code on basilar membrane for frequency
- - - - more depolarization
        
        nerve fibers that receive depolarized info cells fire at increased rate
  - - - more intense sound creates more APs
  - - - Phase locking in auditory nerve
        
        neurons will fire APs every cycle
        
        frequency of sound is the same as frequency of APs
    - - neuron fires at same phase
        not cycle
        
        entire group responds to frequency
        
        tonotopy is still used and phase locking with volley principle
    - - sound wave cycle too fast
        
        frequencies represented by tonotopy only
- - - - sound straight ahead has no delay
        
        detected by brain stem neurons
    - - cannot sense arrival times at both ears
        
        compare phase of sound waves from two ears
    - - high frequencies can't use time delay
        
        sound in ear that's farther away will be less itnense
        
        neurons sensitive to difference in intensity
  - - - sound refelcted off ear curves
        
        directed to auditory canal
- - - - can distinguish b/w cells that respond to stimulation of both ears
- - - - Superior Olive
        crossing over of info
        first point of binaural info
        info travels up through lateral meniscus
        
        Inferior Colliculus
        connects sound to motor
        
        Thalamus
        Medial Geniculate Nucleus
        
        Auditory Cortex
- - - - Loudness
        also influences number of APs