The vestibular system is the sensory system that contributes to our sense of balance and spatial orientation. The system is located in the inner ear and consists of the semicircular canals, the utricle, the saccule, the cupula, ampullae and the cochlea. The vestibular system sends signals to both the nerves in the eyes and the muscles that keep a person upright to maintain a sense of balance.
The system as a whole detects motion, equilibrium and special orientation of the body using the systems of the semicircular canals, utricle and saccule. The utricle and saccule detect the vertical orientation (gravitational pull) of the body and other linear movements. There is one utricle and one saccule in each ear, both located near the center of the vestibular system.
There are three semicircular canals: the anterior canal, the lateral canal and the posterior canal. These canals work together to detect rotational movements. They are located at right angles to each other and are filled with endolymph, a fluid which exerts pressure against the canals’ sensory receptors. When the sensors are triggered, they send impulses to the brain that movement has been detected from whichever canal is stimulated.
When a vestibular system is properly functioning, the vestibular organs on each side of the head send the same impulses to the brain. If they send signals that are inconsistent, a person can feel off-balance or disjointed. If disease attacks the vestibular system or if it is for any reason malfunctioning, the most common symptom is vertigo, which presents as instability and nausea.