Cochlear nerve fibres (magnified)
Neurofibrae cochleares
Sensory (eye & ear)NervesWhole body
- What it is
- Afferent fibres of the spiral ganglion neurons: thick type I fibres (95 per cent) each contact a single inner hair cell, while thin type II fibres branch across many outer hair cells. They leave through the habenula perforata and run to the modiolus.
- Function
- Carry the electrical signal from the hair cells toward the brainstem, each fibre tuned to one frequency.
- Size
- Type I fibres 2-4 micrometres, myelinated; about 30,000 per cochlea.
- Clinical note
- Loud noise can destroy these synapses before any hair cell dies: "hidden hearing loss" with a normal audiogram but poor hearing in background noise.