What is the main action of the Vestibulocochlear Nerve, specifically the Cochlear branch?

The Vestibulocochlear Nerve, particularly its Cochlear branch, is primarily responsible for hearing. This nerve transmits auditory information from the cochlea, which houses the spiral organ (or organ of Corti), to the brain. The spiral organ contains hair cells that convert sound vibrations into electrical signals, which are then sent via the Cochlear branch to the auditory centers in the brain for processing. This function is critical for the perception of sound, including the ability to distinguish different frequencies and loudness.

In contrast, the other options relate to different functions of the nervous system or other aspects of auditory and vestibular functions. Balance and proprioception are primarily associated with the vestibular portion of the vestibulocochlear nerve, rather than the cochlear aspect which focuses solely on auditory processing. Facial expression control is governed by the facial nerve, which innervates the muscles responsible for facial expressions. Lastly, sensory information from the external ear mainly involves the auriculotemporal nerve and not the cochlear branch of the vestibulocochlear nerve.