Sensations of dizziness, lightheadedness and unsteadiness may result from disturbances of any one or a combination of these four systems.
Each system performs certain functions. The inner ear monitors the direction of motions such as turning, stopping, and starting. The eyes monitor the position of the body in space and also assist in the detection of the direction of motion. The skin pressure receptors, such as the feet, monitor the stability of the body in relationship to the ground. The muscle and joint receptors monitor what body parts are moving. The brain and spinal cord process and coordinate the information from all of these systems for maintenance of balance.
The inner ear is that part of the ear that houses the balance chambers. The inner ear is divided into two main compartments. One compartment is the cochlea ("coke-lee-a") which is for hearing. The other compartment consists of the balance chambers: the semicircular canals, the utricle and the saccule. The cochlea and all of the balance chambers are interconnected. The organs within the inner ear are bathed in fluid and contain the delicate nerve endings of balance and hearing.
The function of the balance system
As the head moves, the fluid in the balance chambers moves and pushes against the balance nerve endings. The nerve endings register the change and send electrical signals to the brain by way of the balance (vestibular) nerve. The brain interprets this signal as head movement.
Each inner ear is continuously sending information to the brain regarding the body's position. Balance is maintained by a continuous and equal signal from both inner ears. When one inner ear is damaged, the unequal input to the brain causes a type of dizziness known as vertigo.
The Anatomy of Balance
Dizziness, vertigo, and motion sickness all relate to the sense of balance and equilibrium. Researchers in space and aeronautical medicine call this spatial orientation, because it tells the brain where the body is "in space:" what direction it is pointing, what direction it is moving, and if it is turning or standing still.
Your sense of balance is maintained by a complex interaction of the following parts of the nervous system:
- The inner ears (also called the labyrinth), which monitor the directions of motion, such as turning, or forward-backward, side-to-side, and up-and-down motions.
- The eyes, which monitor where the body is in space (i.e. upside down, rightside up, etc.) and also directions of motion.
- The skin pressure receptors such as in the joints and spine, which tell what part of the body is down and touching the ground.
- The muscle and joint sensory receptors , which tell what parts of the body are moving.
- The central nervous system (the brain and spinal cord), which processes all the bits of information from the four other systems to make some coordinated sense out of it all.
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