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The balance system

How does our balance system work?

The ear has three main parts: the external or outer ear (the visible part on the outside), the middle ear (the main function of which is to transmit sound from the outer to the inner ear), and the inner ear (the labyrinth). The balance system is a complex system of nerves, small tubes called semicircular canals, and fluid inside the labyrinth. It includes parts of the brain and other components.
 

The labyrinth

The labyrinth is located deep inside some of the hardest bones in the skull. It is divided into the cochlea (the organ responsible for hearing) and the vestibular organs (responsible for balance). Because of the close link between the hearing and balance systems, your GP will ask you about your hearing when investigating your dizziness and balance problems.
 
The labyrinth: the inner ear, containing the organs responsible for hearing and balance.
 
The vestibular (balance) systems inform your brain about the movements and position of your head. There are three sets of tubes (semicircular canals) in each vestibular system and these detect when you move your head. There are also two structures called the “otoliths” which inform your brain when your head is moving in a straight line and indicate the position of your head in respect of the pull of gravity. Dizziness or vertigo occurs when the right and left balance systems do not work together in symmetry and your brain thinks your head is moving when it is not. This is why many forms of dizziness are triggered or made worse by moving your head.
 

The structure of the ear

Diagram showing the structure of the ear

Vision and other parts of the balance system

Maintaining balance is a complex function and, although the ear is a very important component in the balance system, other factors play a role. To have a good sense of balance we need to be able to see where we are and be aware of the position of certain key parts of our body in relation to other parts of the body, and in relation to the world around us. For example, your brain needs to know how your feet and legs are positioned in relation to your chest and shoulders. This information is conveyed to your brain by movement and position detectors located in your muscles, tendons and joints, particularly in the neck, ankles, legs and hips. Good binocular vision is the most important system in maintaining balance.
 
A crucial aspect of a good balance system is that your brain can control your balance by using the most reliable information it receives for any given moment or situation. For instance, in the dark, when the information conveyed by your eyes is reduced or unreliable, your brain will use more information from your legs and feet and your inner ear. Alternatively, if you are walking in daylight on a sandy beach, the information coming from your legs and feet will be less reliable and your brain will rely more on your vision and vestibular systems.
 
We almost never have to rely solely on the information provided by the balance organs of the ear. Many people retain a good sense of balance despite inner ear problems due to the complementary support provided by the eyes, and movement and position detectors in our joints and muscles. This is why even people who have lost the function of both inner ears do not entirely lose their sense of balance.
 

The main parts of the balance system:

  • Vestibular systems in the inner ear
  • Vision (our eyes)
  • Movement and position detectors in our joints and muscles


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