Awareness of body balance and movement are monitored by the vestibular system.
The vestibular senses
(the sensations of body rotation and of gravitation and movement) arise in the inner ear; the sense organs are the hair cells that send out signals over the auditory nerve.
The sensation of body rotation arises in the three semicircular canals in the inner ear. Movement of fluid in the canals stimulates hair cells, which send messages to the brain about speed and direction of body rotation. Gravitation and movement sensations are produced by movement of two vestibular sacs in each ear that lie between the semicircular canal and the cochlea. Both sacs are filled with millions of tiny crystals that bend hair cells when moved. In turn, impulses giving a sense of position are sent to the brain. (Motion sickness originates from excessive stimulation of the vestibular organs.)