[Stress]

Any change in the social or physical environment that threatens the needs or interests of a mammal, induces a state of tension ('stress') in the animal. Driven by this tension, the animal changes its behaviour. At the same time, alterations occur in bodily functions. All organs and regulatory systems (central and peripheral nervous systems, endocrine and immune systems) participate in these behaviour-physiological response and are affected in their activities. The character of the reactions (e.g. fight, flight, passivity) is mainly determined by the animals appraisal of the environmental change and of the possible impact of its response. Aim of the reactions is neutralising the threat and gaining control over the environment (adaptation). When this is achieved, the tension recedes. In case the response is unsuccessful, the state of tension persists ('chronic stress'). Prolonged exposure of brain and/or bodily functions to stress can result in pathological states.