Summary
On the basis of the degeneration behaviour two different types of cochlear afferent neurons can be distinguished. About 95% of all cochlear neurons are of the common type I with large myelinated spiral ganglion cells. They show complete retrograde degeneration after transsection of the cochlear nerve and they are exclusively connected to the inner hair cells. The remaining 5% neurons are of type II and do not degenerate after transsection of the cochlear nerve. Their smaller, unmyelinated ganglion cells are clearly distinguished from the type I ganglion cells. They provide the entire afferent nerve supply to the outer hair cells. The functional implications of such a divergent inner hair cell afferent innervation and a convergent outer hair cell afferent innervation are discussed.
Zusammenfassung
Aufgrund des Degenerationsverhaltens können zwei verschiedene Typen von afferenten Cochlearisneuronen unterschieden werden. Ca. 95% aller Cochlearisneuronen entsprechen dem Typ I mit großen bemarkten Spiralganglionzellen. Nach Durchtrennung des Nervus cochlearis im inneren Gehörgang erleiden diese Neuronen eine vollständige retrograde Degeneration und verschwinden. Sie sind ausschließlich mit den inneren Haarzellen verbunden. Die restlichen 5% Cochlearisneuronen sind vom Typ II und degenerieren nicht nach Durchtrennung des Nervus cochlearis. Ihre kleineren, nicht bemarkten Ganglionzellen sind von den Typ I Ganglionzellen klar zu unterscheiden. Die ganze afferente Innervation der äußeren Haarzellen kommt von diesen 5% Typ II Neuronen. Die mögliche funktionelle Bedeutung dieser stark divergenten afferenten Innervation der inneren Haarzellen und der stark konvergenten Innervation der äußeren Haarzellen wird diskutiert.
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Spoendlin, H. Degeneration behaviour of the cochlear nerve. Arch. Klin. Exp. Ohr.-, Nas.- U. Kehlk. Heilk. 200, 275–291 (1971). https://doi.org/10.1007/BF00373310
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DOI: https://doi.org/10.1007/BF00373310