Nociception and autonomic nervous system.

The International Association for the Study of Pain (IASP) defines pain as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage". Pain may also be experienced in absence of noxious stimuli and together with temperature and other bodily feelings constitute the interoception redefined as the sense of the physiological condition of the entire body, not just the viscera. The main characteristic of these feelings is the affective aspect. Emotion, motivation, and consequent behavior connected with these feelings characterize their homeostatic role. This implies an interaction between neural structures involved in pain sensation and autonomic control. The aim of this review is to focus on pain perception, mainly on pain matrix structures' connections with the autonomic nervous system.