![]() ![]() ![]() Basilar membrane width and stiffness vary to control the frequencies best sensed by the IHC. The basilar membrane (BM) is a barrier between scalae, along the edge of which the IHCs and OHCs sit. There are three to four times as many OHCs as IHCs. The outer hair cells (OHC) are minimally innervated by spiral ganglion in slow (unmyelinated) reciprocal communicative bundles (30+ hairs per nerve fiber) this contrasts inner hair cells (IHC) that have only afferent innervation (30+ nerve fibers per one hair) but are heavily connected. These motors (outer hair cells) amplify the traveling wave amplitudes over 40-fold. This causes the cells to be chemically elongated and shrunk ( somatic motor), and hair bundles to shift which, in turn, electrically affects the basilar membrane's movement (hair-bundle motor). Vestibular duct perilymph vibrations bend organ of Corti outer cells (4 lines) causing prestin to be released in cell tips. Vestibular and tympanic ducts are filled with perilymph, and the smaller cochlear duct between them is filled with endolymph, a fluid with a very different ion concentration and voltage. The base of the stapes couples vibrations into the cochlea via the oval window, which vibrates the perilymph liquid (present throughout the inner ear) and causes the round window to bulb out as the oval window bulges in. The middle-ear ossicles further amplify the vibration pressure roughly 20 times. The outer ear funnels sound vibrations to the eardrum, increasing the sound pressure in the middle frequency range. ![]() It includes both the sensory organs (the ears) and the auditory parts of the sensory system. The auditory system is the sensory system for the sense of hearing. How sounds make their way from the source to the brain ![]()
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