The ability to maintain balance depends on information that the brain receives from three different sources—the eyes, the muscles and joints, and the vestibular organs in the inner ears. All three of these sources send information in the form of nerve impulses from sensory receptors, special nerve endings, to your brain.

Each inner ear has a hearing (auditory) component—the cochlea, and a balance (vestibular) component—the vestibular system, consisting of three semicircular canals and a utricle and saccule. Each of the semicircular canals is located in a different plane in space. They are located at right angles to each other and to those on the opposite side of the head.

Inside each fluid-filled semicircular canal is a sensory receptor (cupula) attached at its base. When the head moves, fluid within the semicircular canals stimulates the cupula and the receptor then sends impulses to the brain about the direction of the movement. The utricle and saccule work in similar ways. They are structures that consist of sensory cells that are embedded in a gelatinous structure. Sitting on the gelatinous portion are calcium carbonate crystals called otoconia.  When your body moves up and down or forward and backward, the added mass of the otoconia cause the sensory cells to bend.  This sends impulses to the brain about the direction of the movement.

When the vestibular apparatus on both sides of the head are functioning properly, they send symmetrical impulses to the brain. That is, the impulses coming from the right side agree with the impulses coming from the left side.

All of the sensory input concerning balance, from the eyes, from the muscles and joints, and from the two sides of the vestibular system, is sent to the brainstem, where it is sorted out and integrated with contributions from other parts of the brain.

As integration of all the sensory input takes place, the brainstem sends out impulses along motor-nerve fibers that begin in the brainstem and end in the muscles. These muscles make your head and neck, your eyes, your legs, and the rest of your body move and allow you to maintain your balance and have clear vision while you are moving.