Wave length of each C

The oval window transmits sound vibration from the stapes ossicle to the perilymph within the scala vestibuli. From there it spreads through the helicotrema, and the fluid in the scala tympani finally impinges on the round window. Movements of the round window are generally compensatory to those in the oval window, thus providing the necessary give within the otherwise closed fluid system of the cochlea. The Reissner's and basilar membranes form the flexible membrane boundaries of the scala media and allow it to be displaced by movements in the surrounding fluid. A continuous tone transmitted in this fashion causes a standing wave to form in the cochlear membrane system, in particular in the basilar membrane.

A standing wave produced in basilar membrane is not uniform along its full length (see Fig. 4). Structural features of the basilar membrane influence the wave form. The membrane is relatively narrow and stiff at its base, wide and floppy at its apex. Thus, low-frequency waves, associated with low-pitch sound, produce larger displacements in the apex region of the membrane, whereas high-frequency waves, associated with high-pitch sound, produce larger displacements in the basal portion. This means that hair cells located at different locations along the length of the basilar membrane will be more activated by certain pitches than by others. Different locations are maximally deformed by different frequencies. This relationship between position and pitch results in a tono-topic organization of the hair cells, with high pitch encoded by hair cells near the base and low pitch encoded by cells near the apex. Positional relationships are maintained among all neurons within the auditory pathway, much as the visual pathway is organized in a retinotopic fashion.

Primary auditory nerve cell bodies located in the spiral ganglia near the base of the cochlea send peripheral processes to innervate two types of auditory receptors: inner and outer hair cells. The arrangement of auditory nerve cell bodies within the ganglion and both peripheral and central processes maintain a tonotopic organization.

D. High amplitude pressure waves make loud sounds

D. High amplitude pressure waves make loud sounds

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