CMD 278 Lecture Notes - Lecture 3: Vestibulocochlear Nerve, Audiogram, Stria Vascularis Of Cochlear Duct

• School: URI
• Department: Communicative Disorders
• Course: CMD 278
• Professor: Milner Bethany

Document Summary

There are 2 primary direct current (dc) potentials measured in the cochlea with no stimulation necessary: endocochlear potential, the largest potential, approximately +80mv, seen in the endolymph, generated by stria vascularis. Intracellular resting potential: approximately -70mv, adds to endocochlear potential to create the potential difference across the hair cells b. i. Endocochlear potential (80 mv) + intracellular resting potential (70 mv) = 150 mv. 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 the 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.