The above are what implicate IC in the 'startle response' and ocular reflexes. superior colliculus: orientation and behavior toward objects, as well as eye movements (saccade)) areas, pons (superior cerebellar peduncle: thalamus to cerebellum connection/hear sound and learn behavioral response), spinal cord (periaqueductal grey: hear sound and instinctually move), and thalamus. IC receives inputs not shown, including visual (pretectal area: moves eyes to sound. Ventral nuclei of lateral lemniscus help the inferior colliculus (IC) decode amplitude modulated sounds by giving both phasic and tonic responses (short and long notes, respectively). The lateral lemniscus has three nuclei: dorsal nuclei respond best to bilateral input and have complexity tuned responses intermediate nuclei have broad tuning responses and ventral nuclei have broad and moderately complex tuning curves. Simplified, nerve fibers' signals are transported by bushy cells to the binaural areas in the olivary complex, while signal peaks and valleys are noted by stellate cells, and signal timing is extracted by octopus cells. Cochlear nerve fibers (30,000+) each have a most sensitive frequency and respond over a wide range of levels. Fusiform cells integrate information to determine spectral cues to locations (for example, whether a sound originated from in front or behind). Octopus cells have close to the best temporal precision while firing, they decode the auditory timing code. Stellate (chopper) cells encode sound spectra (peaks and valleys) by spatial neural firing rates based on auditory input strength (rather than frequency). Bushy cells transmit timing info, their shape averages timing jitters. The CN breaks into ventral (VCN) and dorsal (DCN) regions. The trapezoid body is where most of the cochlear nucleus (CN) fibers decussate (cross left to right and vice versa) this cross aids in sound localization. PVO, CPO, RPO, VMPO, ALPO and SPON (inhibited by glycine) are various signalling and inhibiting nuclei. VLPO have the same function as DPO, but act in a different area. LNTB are glycine-immune, used for fast signalling. LSO normalizes sound levels between the ears it uses the sound intensities to help determine sound angle. MSO determines the angle the sound came from by measuring time differences in left and right info. SOC has 14 described nuclei their abbreviation are used here (see Superior olivary complex for their full names). The superior olivary complex (SOC), in the pons, is the first convergence of the left and right cochlear pulses. TM width and stiffness parallels BM's and similarly aids in frequency differentiation. The tectorial membrane (TM) helps facilitate cochlear amplification by stimulating OHC (direct) and IHC (via endolymph vibrations). At the cochlear base the BM is at its narrowest and most stiff (high-frequencies), while at the cochlear apex it is at its widest and least stiff (low-frequencies). 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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