This is from the pain control course in the UK. This theory was developed in the 1960’s by Ronald Melzack and Patrick Wall. The earlier idea is the pain travels up from the sight of the injury and that is it just a purely passive system Upon injury, pain messages originate in nerves associated with the damaged tissue and flow along the peripheral nerves to the spinal cord and on up to the brain. So far, this is roughly the same as to the specificity theory of pain described above.

However, in the gate control theory, before they can reach the brain these pain messages encounter “nerve gates�?in the spinal cord that open or close depending upon a number of factors (possibly including instructions coming down from the brain). When the gates are opening, pain messages “get through�?more or less easily and pain can be intense. When the gates close, pain messages are prevented from reaching the brain.

If you would like to know more here are a few web sighs to look at :-

http://www.spine-health.com/conditions/chronic-pain/modern-ideas-gate-control-theory-chronic-pain

http://en.wikipedia.org/wiki/Gate_control_theory_of_pain

_James