When faced with an emergency, our bodies go through a series of physiological responses that assist us in coping with a stressor. Activation of the fight-or-flight response and hypothalamic–pituitary–adrenal (HPA) system gives us the energy and resources we need to cope with a temporary stressor. Studying these physiological responses, Hans Selye (1956) suggested that the sequence follows the same path no matter the stressor. He found that when the stressor remains, our bodies can no longer adapt. Selye called this sequence the general adaptation syndrome (GAS).