On the basilar membrane are 4 rows of sensory receptor cells called hair cells: 1 row of inner hair cells and 3 rows of outer hair cells, Each hair cell is separated by several supporting cells. Hair cells are so called because of fine apical protrusions called stereocilia. Outer Hair Cells stereocilia Outer Efferent hair cells nel axons of cort Inner hair Cells Supporting cells
On the basilar membrane are 4 rows of sensory receptor cells called hair cells: 1 row of inner hair cells and 3 rows of outer hair cells. Each hair cell is separated by several supporting cells. Hair cells are so- called because of fine apical protrusions called stereocilia. Outer Hair Cells Inner Hair Cells Supporting cells. stereocilia
The stereocilia contact an overlying accessory structure: the tectorial membrane C Spiral organ Hair cells Tectorial membrane of Corti nner Oute ∥∥的 Stereocilia Rods and tunnel of corti 965 Basilar membrane Supporting Spiral lamina Afferent nerve fibers Efferent nerve fibers Spiral ganglion As basilar membrane moves up, hairs are deflected outward causing depolarization of hair cells and increased firing of afferent nerve fibers
The stereocilia contact an overlying accessory structure: the tectorial membrane
Pivot points for tectorial and basilar membranes Shear force Tectorial membrane d displ iNner hair cell Basilar membrane Shear force Downward displacement As the basilar membrane vibrates the stereocilia, at the apex of the sensory hair cells are deflected, by the shearing between the organ of corti and the tectorial membrane lying above it. The QuickTime pivot points of the organ of Corti and Animation de tectorial membrane are off-set, so that when the basilar membrane is displaced, the tectorial membrane moves across the tips of the stereocilia deflecting the hair bundle
As the basilar membrane vibrates, the stereocilia, at the apex of the sensory hair cells are deflected, by the shearing between the organ of Corti and the tectorial membrane lying above it. The pivot points of the organ of Corti and tectorial membrane are off-set, so that when the basilar membrane is displaced, the tectorial membrane moves across the tips of the stereocilia, deflecting the hair bundle. QuickTime™ and a Animation decompressor are needed to see this picture
TEM mem brane actin linker tip link SEM Tip-link Deflection of the hair bundle in the direction of the tallest stereocilia stretches the tip-links located between the tip of the shorter stereocilium and side of the taller stereocilium This opens the transduction channels, depolarizing the hair cell. Deflection of the hair bundle in the opposite direction closes the transduction channels, causing hyperpolarization of the hair cell. All sensory hair cell in the cochlea, vestibular labyrinth and fish lateral line system ty pes operate in similar fashion
Deflection of the hair bundle in the direction of the tallest stereocilia stretches the tip-links located between the tip of the shorter stereocilium and side of the taller stereocilium. This opens the transduction channels, depolarizing the hair cell. Deflection of the hair bundle in the opposite direction closes the transduction channels, causing hyperpolarization of the hair cell. All sensory hair cell in the cochlea, vestibular labyrinth and fish lateral line system types operate in similar fashion. TEM SEM Tip-links QuickTime™ and a GIF decompressor are needed to see this picture
Reissner's membrane Stria vascularis Ko vestibuli +80mv Endo- lv mpl -45 mV tympani 0 mV Depolarization Perilymph media Inner hair cell (②) Potential difference between endolymph and Vesicles inner hair cell cytoplasm= 125 mV Opening of transduction channels leads to a positively- Transmitter charged transduction current influx (largely K) that opens Afferent baso-lateral Ca**+ channels, depolarizing the hair cell and nerve To brain leads to release of neurotransmitters at hair cell base
Potential difference between endolymph and inner hair cell cytoplasm = 125 mV Opening of transduction channels leads to a positively- charged transduction current influx (largely K+) that opens baso-lateral Ca++ channels, depolarizing the hair cell and leads to release of neurotransmitters at hair cell base