What causes pain and how do we stop it? This unit looks at how the human body responds to the release of certain chemicals and as a result feels pain. Pain can be reduced by inhibiting the formation of such chemicals and you will learn how the molecular structure of aspirin has been formulated to help in this process. This study unit is just one of many that can be found on LearningSpace, part of OpenLearn, a collection of open educational resources from The Open University. Published in ePub 2.0.1 format, some feature such as audio, video and linked PDF are not supported by all ePub readers.