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The spiral (cochlear) ganglion is a group of neuron cell bodies in the modiolus, the conical central axis of the cochlea. These bipolar neurons innervate the hair cells of the organ of Corti . They project their axons to the ventral and dorsal cochlear nuclei as the cochlear nerve , a branch of the vestibulocochlear nerve (CN VIII).
The vestibular nerve is one of the two branches of the vestibulocochlear nerve (the cochlear nerve being the other). In humans the vestibular nerve transmits sensory information from vestibular hair cells located in the two otolith organs (the utricle and the saccule) and the three semicircular canals via the vestibular ganglion of Scarpa.
It separates the cochlear duct from the vestibular duct. It helps to transmit vibrations from fluid in the vestibular duct to the cochlear duct. Together with the basilar membrane, it creates a compartment in the cochlea filled with endolymph, which is important for the function of the spiral organ of Corti.
Hair cells are only regenerated after damage. [21] Hair cells in chicks are regenerated just three days after damage is inflicted, and the hair cells fully recover within 30 days. [22] Supporting cells begin to replicate and form hair cells within 18–24 hours after damage, and this process peaks in 2–3 days. [23]
The cochlear nerve, as well as spiral ganglion is situated inside it. The cochlear nerve conducts impulses from the receptors located within the cochlea. The picture shows the osseous labyrinth. The modiolus is not labeled; it's at the axis of the spiral of the cochlea.
The cochlear nerve (also auditory nerve or acoustic nerve) is one of two parts of the vestibulocochlear nerve, a cranial nerve present in amniotes, the other part being the vestibular nerve. The cochlear nerve carries auditory sensory information from the cochlea of the inner ear directly to the brain .
The superior and inferior divisions of the vestibular nerve meet at the ganglion.Thereon, the fibers of second-order neurons of the vestibular nerve merge with those of the cochlear nerve (whose first-order neurons have already synapsed at the spiral ganglion) to proceed towards the CNS as a single unified vestibulocochlear nerve (cranial nerve VIII).
Sensory hearing loss often occurs as a consequence of damaged or deficient cochlear hair cells. [disputed – discuss] Hair cells may be abnormal at birth or damaged during the lifetime of an individual. There are both external causes of damage, including infection, and ototoxic drugs, as well as intrinsic causes, including genetic mutations.