who created the general adaptation syndrome for stress
Hans Selye Selye has acknowledged the influence of Claude Bernard (who developed the idea of milieu intérieur) and Walter Cannon's "homeostasis". Selye conceptualized the physiology of stress as having two components: a set of responses which he called the "general adaptation syndrome", and the development of a pathological state from ongoing, unrelieved stress.
Hypothalamic–pituitary–adrenal axis Studies on people show that the HPA axis is activated in different ways during chronic stress depending on the type of stressor, the person's response to the stressor and other factors. Stressors that are uncontrollable, threaten physical integrity, or involve trauma tend to have a high, flat diurnal profile of cortisol release (with lower-than-normal levels of cortisol in the morning and higher-than-normal levels in the evening) resulting in a high overall level of daily cortisol release. On the other hand, controllable stressors tend to produce higher-than-normal morning cortisol. Stress hormone release tends to decline gradually after a stressor occurs. In post-traumatic stress disorder there appears to be lower-than-normal cortisol release, and it is thought that a blunted hormonal response to stress may predispose a person to develop PTSD.[20]