The physiology of stress and the human body’s response to stress

Stress is an environmental factor that precipitates a potent physiological response involving the autonomic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis. The modern society has posed unprecedented challenges for the human stress experience, as chronic stress exposure, which has become an integral part of societal living, has led to a maladaptive stress response that is associated with a host of diseases such as cardiovascular disease, diabetes, cancer susceptibility, and obesity, among many others. The brain is especially susceptible to the catabolic effects of stress and its glucocorticoid (GC) hormone cortisol, as prolonged exposure to stress or cortisol leads to the development of psychiatric disorders such as anxiety and depression. Chronic stress exacts its toll on behavior by altering the body’s homeostatic cortisol levels as well as the function of brain-specific genes, in part, by epigenetic mechanisms. This chapter will provide a foundational knowledge on the human stress response and the mediating factors that impair behavior.