VESTIBULOCOCHLEAR (VIII) NERVE
VESTIBULOCOCHLEAR CRANIAL NERVE
- It is a pure sensory nerve carrying special somatic afferent fibers.
- Consists of two components (vestibular & cochlear) transmitting sensory information from membranous labyrinth to brain.
- Vestibular component (vestibular nerve) is concerned with epithelium (Balance) and cochlear component (cochlear nerve) is concerned with hearing.
- VIII nerve lies in internal acoustic meatus along with labyrinthine vessels, and sensory (nerve of Wrisberg) roots of VII nerve.
Cochlear nerve and pathway of hearing:
- Cochlear nerve is formed by axons of bipolar neurons of spiral ganglion (cochlear ganglion).
- Cochlear nerve carries impulse from sense organ (organ of corti) to dorsal and ventral cochlear nuclei.
The auditory pathway is as follows:
Auditory pathway ← Auditory radiation ← Medial geniculate body ← Inferior colliculus ← Lateral lemniscus
↑
Hair cells of organ of corti (in cochlea)→Spinal ganglion→Cochlear Nerve→Ventral & dorsal cochlear nuclei→Trapezoid body→Superior olivary complex
Vestibular nerve and vestibular pathway:
- Vestibular nerve is formed by axons of bipolar neurons of scarpa’s ganglion (vestibular ganglion).
- Vestibular nerve ends in the vestibular nuclei.
- These nuclei send fibers to cerebellum, motor nuclei of brain stem (III, IV, VI and IX nerves) and anterior horn cells of spinal cord.
FUNCTION OF 8th CRANIAL NERVE:
- Vestibular component (vestibular nerve)→ Equilibrium & balance
- Cochlear component (cochlear nerve)→ Hearing
Exam Important
- Vestibular component (vestibular nerve)→ Equilibrium & balance
- Cochlear component (cochlear nerve)→ Hearing.
- Trapezoid body is involved in auditory pathway (lateral lemniscus system).
- Auditory transmission is via Lateral lemniscus.
- Auditory pathway passes through Medial geniculate body.
- Scala tympani is supplied by Vestibulocochlear nerve.
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