ABSTRACT
The ability to illicit painful sensation is essential for the well-being of any organism, since its function is to prevent harm. Classic thinking proposed that a noxious stimulus travelled by a series of pathways to the brain, where the region of potential injury could be identified and if necessary withdrawn, by either voluntary or unconscious reflex action. It is now known that before a noxious sensation is elicited as pain it must be processed by higher centres within the central nervous system (CNS). A definition of pain that reflects this states that pain is ‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage’. This definition takes into account the fact that emotional and evaluative processes come into play and that although tissue damage may not necessarily be taking place, the sensation may feel as such.
