Organisms survive by maintaining homeostasis, a complex, dynamic, and harmonious equilibrium. This equilibrium is constantly challenged or threatened by disturbing factors or stressors. For survival, organisms have to actively react with an adaptational or stress response, which should lead to the preservation or reestablishment of the steady state. Stressors are qualitatively and quantitatively very diverse in nature. They are either external or internal in origin and may be caused by psychological (e.g., feelings of fear) or physiological (e.g., exercise-induced glucose shortage) events.