CMD 278 Lecture Notes - Lecture 8: Stria Vascularis Of Cochlear Duct, Vestibulocochlear Nerve, Cochlear Nucleus
Document Summary
There are 2 priamry direct current (dc) potentials measured in the cochlea with no stimulation necessary: endocochlear potential. Generated by stria vascularis: intracellular resting potential. Adds to endocochlear potential to create the potential difference across the hair cells. Endocochlear potential (80mv) + intracellular resting potential (70mv) = 150mv. There are 3 potentials that are seen in response to stimulation: cochlear microphonic: source = top end of hair cells. Alternating current (ac) potential that varies in the same way as the stimulus. Present only when the stimulus is present: summating potential: source = hair cells. Change in the voltage can be positive or negative. Present only when stimulus is present: whole-nerve action potential: source = cn viii. Response only seen at onset of abrupt signal. Response represents a synchronized discharge of several cn viii nerve fibers. 20db 20db 10db 15db softest levels that cause cell to fire: this process is repeated at many different frequencies, thus generating a tuning curve.
