How does our sense of balance work?

The ear is not just a sensory organ for picking up sound waves and allowing us to hear. It is also essential to our sense of balance: inside of the inner ear is the vestibular system (the organ of balance). It is made up of three fluid-filled canals – the semicircular canals – as well as the otolith organs.

Each of the semicircular canals leads to a small chamber that has small hairs cells in it. These chambers are also called ampullae. When the head moves, the hairs are pulled by the fluid into one or more of the semicircular canals. The hairs sense this movement and then send nerve signals to the brain.

Each of the three semicircular canals is responsible for a specific direction of head movement: one registers when the head nods up or down, one when the head rotates to the right or left, and one when the head turns sideways.

The otolith organs, which are the other part of the vestibular system, are two pouches that are also filled with fluid. They sit sideways below the semicircular canals and have a similar function. These two pouches are also lined with small hairs. Small crystals attached to the hairs move through the fluid when the head tilts. When this happens they rub along the hairs, which sense this movement and then send nerve signals to the brain.

Information coming from the vestibular system is processed in the brain and then sent on to other organs that need this information, for example the eyes, joints or muscles. This allows us to keep our balance and maintain spatial orientation. In some situations, for example on a ship or airplane, messages that do not match up get sent to the brain by different organs, for instance the eyes and the organ of balance. This can cause us to feel unwell, dizzy or nauseous.

The vestibular system is especially sensitive in children, but with age it reacts more slowly to movements. Inner ear infections and other problems may also affect the functioning of our sense of balance.

Author: Institute for Quality and Efficiency in Health Care (IQWiG)

© IQWiG (Institute for Quality and Efficiency in Health Care) Last update of this website: 05/11/2012