Balance & MS 2 of 5

How does balance work?

Good balance needs many different parts of the body to work together effectively.  It might be helpful to think of these different parts of balance being grouped into input, processing, and output.






Large image: Balance diagram (54 kb)  

There are three main input systems working to keep the body balanced, constantly feeding information to the brain through nerve fibres.

The three systems are:

  

• The eyes – the ‘visual system’. The eyes provide information about where the body is, the direction it is pointing in, what direction it is moving and whether the body is turning or is standing still.

• Part of the inner ear and its connections to the brain – the ‘vestibular system’. The inner ear is deep into the ear, beyond the ear drum, and it has two important roles. One is to process sounds that we hear. The other is to measure movement of the head, rather like a complicated version of spirit levels used in DIY. (One of the main parts of this system in the inner ear is called the ‘vestibule’, which is where the ‘vestibular system’ gets its name.)

• Sensors in joints, muscles and skin – the ‘proprioceptive system’. All over the body there are sensors providing information on motion, position and pressure.  For example, messages from the skin on the soles of the feet help the brain to balance the body when standing up: too much pressure on the front of the foot is a signal the body is falling forwards; too much pressure on the heel signals that the body is tilting backwards.

The brain processes the information it receives, making sense of all the input messages, to work out where the body is and how it is moving.  There is no single part of the brain responsible for this processing, but areas called the ‘cerebellum’ and the ‘brainstem’ play a major role in balance, including helping to control the body’s overall coordination.

Having processed the information it receives, the brain sends out messages – back along nerve fibres, through the spinal cord and out to the muscles.  These outputs adjust to the movement and position of the body in its changing surroundings, keeping the body balanced.

Adapted from the Multiple Sclerosis Society in the United Kingdom