Anatomy And Physiology
Vestibular System

Anatomy Physiology

Vestibular System
Barbara Zarrella's image for:
"Anatomy Physiology"
Caption: Vestibular System
Image by: National Institute of Health
© National Institute of Health Medical Arts

The vestibular system is minuscule in size when compared to the respiratory or neurological systems, but any abnormality within this system can cause major problems.  It is involved in maintaining balance, posture, as well as a sense of orientation in space. It enables an individual to stand, focus on a singular object even when moving as well as being able to move without falling. That is quite an impressive job for such a small system.

The system location and structure:

Looking at the structure of this system, it seems like a maze set into the middle ear, called the labyrinth. At one end, this maze is made of bone, soft tissue as well as an intricate cluster of loops, pouches and the otolithic organs. At the opposite end there is a snail-shaped organ, the cochlea, which enables hearing.


The vestibular system needs other organs in order to fully function. It connects to other sensorimotor systems of the body such as the visual system (eyes) and the skeletal system (bones and joints). When it comes to maintaining the position of the body, the vestibular system detects mechanical forces such as gravity that affect movement.  

The three fluid-filled semicircular canals that are arranged at right angles to each other, tell the brain when the head rotates or makes a circular movement. At the base of these canals there is a base containing a raindrop-shaped structure called the cupula. These chambers are filled with a viscous fluid and small particles called otoliths. Movement causes the particles to move over small hair cells called stereocilia, in the cupula. It is the movement of the particles over the hair cells that sends signals to the brain.

There are two other fluid-filled pouches located between the cochlea and the semicircular canals. They are the utricle and saccule, whose job is to let the brain known when the body is moving in a straight line; in the act of standing up, ride in a car or bike. They also tell the brain the position of the head when sitting up, leaning back or lying down, again using their awareness of gravity.

Again, there are sensory hair cells (stereocilia) and now grains made of calcium carbonate called otoconia. Again, as the head tilts, gravity causes the grains to move the stereocilia, which signals the position of the head to the brain. All this interaction of particles within the small fluid-filled pouches of the vestibular system work with the brain as it works in conjunction with the eyes to keep the vision clear, and not blurry. The sensory receptors of the skeletal system also respond to the signals of the vestibular system to help keep balanced, whether still or walking. The brain processes all these signals in order to control balance.

Balance disorders:

The National Institute of Health, in the division on “Deafness and Other Communication Disorders,” lists the symptoms of a balance disorder. They are quoted below.

“If your balance is impaired, you may feel as if the room is spinning. You may stagger when you try to walk or teeter or fall when you try to stand up. Some of the symptoms you might experience are:

•  Dizziness or vertigo (a spinning sensation)
•  Falling or feeling as if you are going to fall
•  Lightheadedness, faintness, or a floating sensation
•  Blurred vision
•  Confusion or disorientation

Other symptoms are nausea and vomiting, diarrhea, changes in heart rate and blood pressure, and fear, anxiety, or panic. Some people also feel tired, depressed, or unable to concentrate. Symptoms may come and go over short time periods or last for longer periods of time.”

Types of balance disorders:

There are a number of different balance disorders. Some are temporary and others are chronic. Various medicines can also cause imbalance problems. Several are listed and briefly explained below.

•  Labyrinthitis: inner ear infection that may accompany an upper respiratory infection.
•  Meniere’s disease: connected the the fluid volume within the inner ear
•  Positional vertigo: a brief but intense episode of vertigo caused by certain movements
•  Vestibular neuronitis: inflammation of the vestibular nerve, sometimes caused by a virus.

Diagnosis is not always simple. An otolaryngologist or Ears, Nose and Throat doctor, commonly called and ENT usually does the tests. These include a hearing test, blood tests, and an electronystagmogram. A cat scan or MRI as well as a posturography may be ordered.

Times to seek help:

As listed on the National Institute of Health site, here are questions that may help an individual determine if they need to medical seek help.

•  Do I feel unsteady?
•  Do I feel as if the room is spinning around me?
•  Do I feel as if I'm moving when I know I'm sitting or standing still?
•  Do I lose my balance and fall?
•  Do I feel as if I'm falling?
•  Do I feel “lightheaded” or as if I might faint?
•  Do I have blurred vision?
•  Do I ever feel disoriented, such as losing my sense of time or where I am?

A balance disorder is not something to ignore. It can be diagnosed and treated. Sometimes simple changes in lifestyle may be needed. There are things that can be done within the home to help prevent falls. Low-heeled shoes, use of a cane may be needed for some disorders. Certain conditions at work may need modification, perhaps just temporarily. Driving may be considered hazardous. Not all disorders are permanent. A proper diagnosis must be made and proper treatment must be given.

More about this author: Barbara Zarrella

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