The auditory system is exteroceptive and concerned with perception of sound. The vestibular system, in contrast, is proprioceptive and concerned with the maintenance of equilibrium and orientation of the body in space and, hence, involved in motor activities. The receptors (mechanoreceptors) are hair cells located within specialized neuroepithelial structures. They are responsible for converting mechanical energy in the form of displacement of their surface elements caused by sound waves (for hearing) and head movements (for balance) into electrochemical energy to be transmitted to the auditory (cochlear) or vestibular root of the vestibulocochlear nerve (cranial n.VIII), respectively. The hair cells are located within the membranous labyrinth of the inner ear, which is a closed tubular system filled with endolymph. The auditory hair cells are in the spiral organ of Corti in the cochlea.