The other two sensory organs supplied by the vestibular neurons are the maculae of the saccule and utricle. Hair cells of the cristae activate afferent receptors in response to rotational acceleration. Three of these are the cristae located in the ampullae of the semicircular canals. The vestibular ganglion houses the cell bodies of the bipolar neurons and extends processes to five sensory organs. The vestibular nerve travels from the vestibular system of the inner ear. The exact mechanism by which sound is transmitted by the neurons of the cochlear nerve is uncertain the two competing theories are place theory and temporal theory. It is the inner hair cells of the organ of Corti that are responsible for activation of afferent receptors in response to pressure waves reaching the basilar membrane through the transduction of sound. Processes from the organ of Corti conduct afferent transmission to the spiral ganglia. The cochlear nerve travels away from the cochlea of the inner ear where it starts as the spiral ganglia. The vestibulocochlear nerve is accompanied by the labyrinthine artery, which usually branches off from the anterior inferior cerebellar artery at the cerebellopontine angle, and then goes with the 7th nerve through the internal acoustic meatus to the internal ear. This junction between the pons, medulla, and cerebellum that contains the 8th nerve is called the cerebellopontine angle. The 8th cranial nerve runs between the base of the pons and medulla oblongata (the lower portion of the brainstem). The vestibulocochlear nerve consists mostly of bipolar neurons and splits into two large divisions: the cochlear nerve and the vestibular nerve.Ĭranial nerve 8, the vestibulocochlear nerve, goes to the middle portion of the brainstem called the pons (which then is largely composed of fibers going to the cerebellum). Through olivocochlear fibers, it also transmits motor and modulatory information from the superior olivary complex in the brainstem to the cochlea. The results can be used to explain deviations in whole-nerve recordings in abnormal cochleas.The vestibulocochlear nerve or auditory vestibular nerve, also known as the eighth cranial nerve, cranial nerve VIII, or simply CN VIII, is a cranial nerve that transmits sound and equilibrium (balance) information from the inner ear to the brain. The various features in the click responses were in most cases consistent with the type of FTC. PSTHs for type I have longer dominant-peak latencies and smaller amplitudes PSTHs for type II were normal well above the fiber’s threshold PSTHs for type III revealed remarkable patterns with multiple peaks, part of them with a latency strongly varying with polarity PSTHs for type IV showed narrow peaks and steep amplitude/intensity curves PSTHs for type V showed a multiple peaked pattern and large amplitudes and steep amplitude/intensity curves to rarefaction polarity. The click PSTHs of abnormal fibers were compared to normal PSTHs at equal sound-pressure levels, and various abnormal trends were found corresponding to the type of FTC. Type I is elevated as a whole, type II has an elevated (and often broadened) tip and a tail at normal level, type III has low thresholds in the tail (often hypersensitive), type IV represents a flat tuning, and type V has no tip but shows a clear appearance of the tail (often hypersensitive). Five types of abnormal FTCs are distinguished. The PSTHs found in fibers with elevated thresholds are discussed in relation to the frequency threshold curves (FTCs) measured in these fibers. Poststimulus time histograms (PSTHs) were recorded for various click intensities and for the two click polarities. This paper describes auditory-nerve single-fiber responses to clicks in noise-damaged cochleas.
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