The Anatomy and Physiology of the Pain System

The peripheral and central nervous systems work in concert to alert us to touch and/or painful stimulation. Peripheral inflammatory mediators alter the threshold of primary sensory neurons and anatomically may restrict pain to the site of injury. However, in chronicity, the responsiveness of sensory nerve endings increases in magnitude and this impacts central processing. The physiology and anatomy of the pain system is altered and spinal events, controlling final pain perception, are maladaptive. In this refresher course we will discuss the intricate mechanisms that underlie afferent nerve stimulation, peripheral and central sensitisation and spinal cord/brain encoding of pain. Further we will discuss ''what does all this mean to the clinic?'' Peripheral and central mechanisms of plasticity contribute to the establishment and/or maintenance of chronic pain states, which manifest clinically in patients as hyperalgesia and allodynia. The clinical relevance of the pathways discussed will be explained in terms of their translational relevance and thus their potential to reveal novel therapeutic targets.