Testing to determine if the cochlea or related structures are involved in hearing loss involves the Rinne and Weber tests. This permits the interpretation of various frequencies of sound based on the tonotopic area along the cochlea (high frequencies at the base and low frequencies closer to the apex) that resonates with the vibration the most. The frequency of the vibration traveling through the perilymph will correspond to an area along the cochlea that is maximally stimulated. The result of the hair cells bending against the tectorial membrane is the depolarization of the attached nerve fibers. The organ of Corti contains hair cells that respond to vibration by brushing their stereocilia against a fixed structure called the tectorial membrane. The difference in width and thickness of the basilar membrane between the base and the apex of the cochlea (BM narrow at the base and wide at the apex) allows for the perception of sounds with a wide frequency range (20 to 20,000 Hz). Vibrations traveling through perilymph in the scala vestibuli pass through the Reissner membrane and into the endolymph of the cochlear duct, eventually vibrating the organ of Corti. The basilar membrane contains a specialized structure known as the organ of Corti that plays a key role in auditory transduction. The structure separating the scala tympani from the cochlear duct is known as the basilar membrane. The Reissner membrane separates the scala vestibuli from the cochlear duct and the stria vascularis, specialized cells lining the lateral wall of the cochlear duct. The Reissner membrane maintains the differences in ion concentration between the endolymph and perilymph. This positive potential results from high potassium ion concentration and low sodium ion concentration compared to the surrounding perilymph. This is another hollow, bony tube that contains a fluid known as endolymph that has a higher positive potential than the surrounding perilymph. The cochlear duct lies between the scala vestibuli and scala tympani. The vibrations then travel from the apex to the base through another hollow, bony tube called the scala tympani.Īt the end of the scala tympani, the vibrations within the perilymph displace the round window. The vibrations travel up the cochlea to the apex through a hollow bony tube known as the scala vestibuli. The footplate of the stapes contacts the oval window in a piston-like motion that results in the transmission of vibrations to a fluid called perilymph within the cochlea. These vibrations are then transferred to the middle ear along the ossicular chain consisting of the malleus, incus, and stapes. The present data allowed calculations of the individual cochlear input impedances.The process of auditory transduction begins with sound waves entering the external acoustic meatus and striking the tympanic membrane, resulting in vibration. No evidence was found for the hypothesis that dips in the piston velocity are filled by peaks in tilt in a systematic way to produce a smooth middle ear pressure gain function. Combining the vibration measurements with an anatomical shape measurement from a micro-CT (CT: computed tomography) scan the piston-like motion and the tilt of the footplate was calculated and correlated to the corresponding scala vestibuli pressure curves. Successively the three-dimensional motion of the stapes was measured in the same animal. Is tilt functional contributing to the pressure in the scala vestibuli and helping in smoothing the pressure gain? In experiments on gerbil the pressure in the scala vestibuli directly behind the footplate was measured while recording simultaneously the pressure produced by the sound source in the ear canal. Separately it was shown that the pressure gain between ear canal and scala vestibuli was a remarkably flat and smooth function of frequency. Tilt and piston components vary with frequency.

It was shown that the mode of vibration of the stapes has a predominant piston component but rotations producing tilt of the footplate are also present.

Scala vestibuli