2014 Inner Ear Physiology

Example test questionTravelling wave and the place principle

HHMI Cochlea animation (scroll to the very bottom of the list)

  • in response to a simple sinusoidal stimulus, the basilar membrane resonates in a "travelling wave" that gradually grows in amplitude as it moves along the cochlear duct: away from the stapes (base), toward the helicotrema (apex)
    • same direction of travel is observed if the sound is introduced into the apex of the cochlea instead of the base

  • THE ENTIRE BASILAR MEMBRANE DOESN'T VIBRATE IN RESPONSE TO EVERY FREQUENCY OF A PARTICULAR SOUND!

  • for a pariticular frequency, basilar membrane vibration reaches a peak amplitude at a specific point that is determined by the resonant properties (acoustic impedance) of the basilar membrane at each point

  • both passive (structural) and active (energy requiring) processes establish the location of the peak vibration
Travelling wave
Place principle
Critical facts icon
  • PLACE PRINCIPLE: the peak of the travelling wave occurs at a different place along the basilar membrane for each frequency (the basilar membrane movement is said to be “tuned”)

    • low frequencies peak near the apex; high frequencies near the base

  • as a result of this spectral analysis, complex stimuli produce vibration patterns where the component frequencies are represented in different locations along the basilar membrane

  • for "his discoveries of the physical mechanism of stimulation within the cochlea", Georg von Bekesy was awarded the 1961 Nobel prize in Physiology or Medicine
Email: Dr. Janet Fitzakerley | ©2014 University of Minnesota Medical School Duluth | Last modified: 15-feb-14 9:04 PM