The vestibular function controls balance and equilibrium in mammals. The vestibular function of the body processes sensory information and alerts the body to changes in movement via the central nervous system. Disorders of the vestibular function lead to vertigo, dizziness and other problems, causing discomfort and making life miserable for sufferers.
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Description
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The vestibular function is processed in the inner ear. To move properly, mammals need to process complex information instantly. The vestibular system processes information about head and body movements along with their position in space. This information is passed along the central nervous system to coordinate muscles and nerves to respond accordingly. The vestibular function is primarily a reflex and unconscious, meaning the brain processes it automatically.
How The Vestibular System Functions
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The eyes relay information about where the body is moving. The vestibular system operates through five functions of the nervous system:
The inner ears monitor the body's motions like turning, rolling, forward-backward, side-to-side and up-and-down movements. The portion of the inner ear involved in this processing is called the labyrinth.
The eyes interpret direction of movement and register where the body is in space, such as upside down, right-side up, laying down and standing up.
Skin assists with receptors located in the joints and spinal column to relay which part of the body is touching the ground.
Muscles and joints signal back information on which parts of the body are in motion.
The central nervous system--made up of the brain and spinal cord--processes the information received from those sensory inputs.
Physiology
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The vestibular system is interpreting this body's movements. With the information received from the four input locations, the vestibular system uses the information to guide acceleration and coordinate eye movements within the head. The structure of the inner ear allows for subtle movements to be detected. Side-to-side information is provided by the ears' semicircular canals. Tiny hairs within the ear move or rest with the body depending on their location. With each movement, the hairs trigger neurons to relay that information to the brain.
Other parts of the body help keep orientation stable. The vestibulo-ocular reflex--or the eyes' interpretation of movement--helps the eyes fixate on a moving object and move the head in turn. Other cells in the eye muscles called extraocular muscle nuclei allow the eye to stabilize despite movements of the head. This allows the eyes to remain fixed even though the head may be nodding or shaking, for example. The vestibulospinal reflex guides information received from the muscles and joints to create posture and stability. These tell the muscles to stand or sit in relation to gravity.
Vestibular Disturbances
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Spinning can cause dizziness because the body is confused about where it is in space. Everyone experiences vestibular disturbances at one point or another. These include motion sickness or simply dizziness. Vertigo is the body interpreting movement that isn't there. Vestibular system disturbances are the result of the brain receiving conflicting information from the other four systems. Vestibular disturbances are caused by simple things--such as spinning on a swing or driving on a mountain road--or less benign causes including infection or injury.
Vestibular Disorders
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Motion sickness is a treatable vestibular function disturbance. Most disturbances to the vestibular system are treated simply with simple actions such as not reading while in a car or watching the horizon while on a ship. Motion-sickness medications are available to avoid the feeling the effects of the disturbance. Mal de débarquement is a problem when the feeling of a car, train, plane or boat continues after traveling, and taking a walk can help to readjust the body.
Some vestibular disorders, however, are serious and require a doctor's care. Complaints of dizziness are among the most common reasons patients visit doctors. Ménière's disease is the abnormal accumulation of fluid in the semicircular canals and results in long-term spinning, dizziness and hearing loss. Vertigo is thought to be a loss of inner-ear fluid. Inner-ear infections can cause labyrinthitis, or an inflamed inner ear. For these severe cases, treatment from a doctor is necessary.
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