Anatomy: Vestibulocochlear Nerve

1. VESTIBULOCOCHLEAR NERVE
ANATOMY

2. VESTIBULOCOCHLEAR NERVE
CN VIII: ANATOMICAL COURSE
▸ The vestibulocochlear nerve is the eighth paired cranial nerve
▸ It is comprised of two parts – vestibular fibres and cochlear fibres
▸ Both have a purely sensory function
▸ The vestibular and cochlear portions of the vestibulocochlear nerve are
functionally discrete, and so originate from different nuclei in the brain:
▸ Vestibular component – arises from the vestibular nuclei complex in
the pons and medulla
▸ Cochlear component – arises from the ventral and dorsal cochlear
nuclei, situated in the inferior cerebellar peduncle

3. VESTIBULOCOCHLEAR NERVE
CN VIII: ANATOMICAL COURSE
▸ Both sets of fibres combine in the pons to form the vestibulocochlear nerve
▸ The nerve emerges from the brain at the cerebellopontine angle and exits the
cranium via the internal acoustic meatus of the temporal bone
▸ Within the distal aspect of the internal acoustic meatus, the vestibulocochlear
nerve splits, forming the vestibular nerve and the cochlear nerve
▸ The vestibular nerve innervates the vestibular system of the inner ear, which is
responsible for detecting balance
▸ The cochlear nerve travels to cochlea of the inner ear, forming the spiral
ganglia which serve the sense of hearing

4. https://teachmeanatomy.info/head/cranial-nerves/vestibulocochlear/

5. https://teachmeanatomy.info/head/cranial-nerves/vestibulocochlear/

6. VESTIBULOCOCHLEAR NERVE
CN VIII: SPECIAL SENSORY FUNCTIONS
▸ The vestibulocochlear nerve is unusual in
that it primarily consists of bipolar neurones
▸ It is responsible for the special senses
▸ hearing (via the cochlear nerve)
▸ balance (via the vestibular nerve)

7. VESTIBULOCOCHLEAR NERVE
CN VIII: SPECIAL SENSORY FUNCTIONS - HEARING
▸ The cochlea detects the magnitude and frequency of
sound waves
▸ The inner hair cells of the organ of Corti activate ion
channels in response to vibrations of the basilar
membrane
▸ Action potentials travel from the spiral ganglia, which
house the cell bodies of neurones of the cochlear
nerve

8. VESTIBULOCOCHLEAR NERVE
CN VIII: SPECIAL SENSORY FUNCTIONS - HEARING
▸ The magnitude of the sound determines how much the
membrane vibrates and thereby how often action
potentials are triggered
▸ Louder sounds cause the basilar membrane to vibrate
more, resulting in action potentials being transmitted
from the spiral ganglia more often, and vice versa
▸ The frequency of the sound is coded by the position of
the activated inner hair cells along the basilar membrane

9. VESTIBULOCOCHLEAR NERVE
CN VIII: SPECIAL SENSORY FUNCTIONS - EQUILIBRIUM (BALANCE)
▸ The vestibular apparatus senses changes in the position of
the head in relation to gravity
▸ The vestibular hair cells are located in the otolith organs
(the utricule and saccule), where they detect linear
movements of the head, as well as in the three semicircular
canals, where they detect rotational movements of the head
▸ The cell bodies of the vestibular nerve are located in
the vestibular ganglion which is housed in the outer part of
the internal acoustic meatus

10. VESTIBULOCOCHLEAR NERVE
CN VIII: SPECIAL SENSORY FUNCTIONS - EQUILIBRIUM (BALANCE)
▸ Information about the position of the head is used
to coordinate balance and the vestibulo-ocular reflex
▸ The vestibulo-ocular reflex (also called the oculocephalic
reflex) allows images on the retina to be stabilized when the
head is turning by moving the eyes in the opposite direction
▸ It can be demonstrated by holding one finger still at a
comfortable distance in front of the pt and asking the pt to
turn their head from side to side staying focused on the
finger

11. https://teachmeanatomy.info/head/cranial-nerves/vestibulocochlear/

12. https://teachmeanatomy.info/head/cranial-nerves/vestibulocochlear/

13. https://teachmeanatomy.info/head/cranial-nerves/vestibulocochlear/

14. References
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vestibulocochlear/
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