Cochlear electrophysiology
Sponsored Links
This presentation is the property of its rightful owner.
1 / 7

Cochlear Electrophysiology PowerPoint PPT Presentation


  • 146 Views
  • Uploaded on
  • Presentation posted in: General

Cochlear Electrophysiology. Zemlin pp. 489-494. Electrical Potentials. DC vs. AC Direct Current = stimulus doesn’t change with time, constant; i.e. battery Alternating Current = always changing over time, looks like a sine wave Stimulus Dependent vs. Stimulus Independent

Download Presentation

Cochlear Electrophysiology

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Cochlear Electrophysiology

Zemlin pp. 489-494


Electrical Potentials

  • DC vs. AC

    • Direct Current = stimulus doesn’t change with time, constant; i.e. battery

    • Alternating Current = always changing over time, looks like a sine wave

  • Stimulus Dependent vs. Stimulus Independent

    • Stimulus Dependent = potentials only present if there is an acoustical sound present

    • Stimulus Independent = potentials always present with and without acoustical stimuli


Stimulus Independent

EP

IP

Stimulus Dependent

SP

CM

AP

Stimulus Independent vs. Dependent


Three DC Potentials

  • Endocochlear Potential (EP)

    • Békésy discovered EP by putting the electrode in the scala media and discovered a +100 mV potential with respect to a neutral point on the body

    • Tasaki discovered EP was due to the Stria Vascularis

  • Intracellular Potential (IP) or organ of corti potential

    • Recorded -50 mV inside cells of organ of corti

  • Summating Potential (SP)

    • DC that is only during very loud intensities of acoustic stimulation


+100 mV

Reticular Lamina

-50 mV


Two AC Potentials

  • Cochlear Microphonic (CM)

    • Reproduces frequency and waveform of a sinusoid perfectly

    • Fig. 6-115 (p. 492)

    • Generated from OHC

  • Action Potential (AP)

    • Electrical activity from the VIII Nerve

    • Can be measured from anywhere in the cochlea or in the auditory nerve


Differential Electrodes

  • Measure the CM, we also measure the AP unless we use differential electrodes

  • Tasaki (1954) was able to separate the CM & AP by using differential pair of electrodes

    • One electrode above reticular lamina (Scala Media or Scala Vestibuli) and the other electrode in the Scala Tympani

    • By changing the polarity, the AP cancels out, while the CM is doubled in amplitude

  • This proved Békésy’s Traveling Wave Theory


  • Login