The eight cranial nerve (also known as the vestibulocochlear nerve) consists of two portions, the vestibular portion and the cochlear portion.  The vestibular portion is responsible for responding to rotational and linear acceleration, which helps maintain equilibrium and body orientation in space.  Semicircular canals contain endolymph, which during movement, displaces small hair cells, which in turn send a signal through the vestibular nerve.  The cochlea is responsible for hearing, as it converts sound waves into signals in the cochlear neurons.