ABSTRACT
The challenge of chronic pain states The sensory system for pain consists of a population of receptors, primary afferent neurones, neurones of the dorsal root of the spinal cord and a pathway to the midbrain, thalamus and cortex via the spinothalamic tract on the opposite side of the spinal cord. Knowledge of the anatomy of pain pathways (a result of studies of cases with damage to nerve pathways and experimental observation) is detailed, but understanding of how the behaviour of the sensory system for pain changes with nerve damage or persistent stimulation is rudimentary. In contrast to the other sensory systems, pain is not a line-labelled, modality-specific, hardwired system, but one in which the relationship between input (stimulus) and output (response) is variable. This variability has led to the development of ‘models’, such as the gate control model to explain the sensory system for pain.
