CN VIII and central Auditory nervous system

  1. Structure of auditory nerve
    • -afferent and efferent fibers gather in a twisted bundle within the modiolus, which is the conically shaped central core of the cochlea
    • -fibers from outside of bundle are for high Hz
    • -fibers from inside or apex of bundle are for low Hz
  2. Bioelectric code chain of reaction
    • 1.mechanical deformation of stereocilia produces an electric potential which causes a liberation of neurotransmitters which initiate an electric potential  in the auditory nerve.
    • 2.neural spikes are produces that travel along the nerve to the cochlear nucleus.  spike rate is proportionate to the size of BM displacement
    • 3. the action potential of the whole auditory nerve is a combination of the spikes of many individual neurons
  3. encoding the acoustic signal: intensity
    • as amp goes up so does the rate of firing(#of spikes/sec)
    • -low intensities= the signal activates neurons at or near the characteristic freq
    • -as intensity goes up more fibres at or near the characteristic freq start to fire too.
  4. encoding the acoustic signal: frequency
    the auditory nerve is organized so that each freq corresponds to a place within the nerve bundle.
  5. tonotopic organization
    mapping freq of a sound wave to a place of max activity within an anatomical structure
  6. Central auditory nervous system pathway
    cochlea -> cochlear nucleus -> superior olives of the pons -> inferior colliculi -> medial geniculate body -> Auditory cortex
  7. Heschl's gyrus
    • primary auditory area of cortex
    • -low freq more lateral
    • -high freq more medial
    • there is a spatial component to freq representation in the cortex
Card Set
CN VIII and central Auditory nervous system
CN VIII and central Auditory nervous system