![]() ![]() Traveling waves Transmission of sound waves in the cochlea ![]() Intensity analysis: by a degree of displacement of the basilar membrane which is directly proportionate to the amplitude of action potential.Pitch analysis: each group of basilar fibers responds to a specific frequency.Transduction: changing sound pressure into an action potential.Transmission of sound waves from the oval window to the organ of Corti.As a result, the thick, short fibers near the oval window will vibrate with high-frequency sounds, while the long thin fibers near the apex will vibrate with sounds of low frequency. The diameter of the fibers, on the other hand, decreases from the base towards the apex. Their lengths increase progressively from the base towards the apex of the cochlea. The basilar membrane: It contains about 25000 stiff elastic basilar fibers. It serves as a major driving force for signal transduction, The i ntracellular recording reveals that the hair cells have a resting potential of approximately – 40 to – 60 mv, Therefore, the net potential difference across the hair cell border is 120 to 140 mv, The high electrical potential at the tips of the stereocilia increases their ability to respond to the slightest sound they are highly excitable.ģ. ![]() This difference is called endocochlear potential. This accounts for the fact that the scala media is positive by 80 millivolts (mv) relative to the scala vestibuli or scala tympani at rest. It continuously secretes K + in the endolymph. Cells of the stria vascularis have a high concentration of Na +-K + ATPase. Stria vascularis: It is a highly vascular structure surrounding the scala media. Neurons of the spiral ganglion within the modiolus send their processes that arborize at the bases of hair cells these fibers transmit electrical changes generated by hair cells to the afferent ascending auditory nerve.Ģ. Covering the rows of hair cells is a tectorial membrane in which their tips or the stereocilia are embedded. There are 20,000 outer hair cells and 3500 inner hair cells in the human cochlea. ![]()
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