The concept of homeostasis, the maintenance of the internal physiological environment of an organism within tolerable limits, is well established in medicine and physiology. In contrast, allostasis is a relatively new idea of ‘viability through change’. With allostatic regulation by cephalic involvement, the body adapts to potentially diverse and dangerous situations through the activation of neural, hormonal, or immunological mechanisms. Allostasis explains how regulatory events maintain organismic viability, or not, in diverse contexts with varying set points of bodily needs and competing motivations. This book introduces the concept of allostasis and sets it alongside traditional views of homeostasis. It addresses basic regulatory systems and examines the behavior of bodily regulation under duress. The basic concepts of physiological homeostasis are integrated with disorders like depression, stress, anxiety and addiction. It will therefore appeal to graduate students, medical students and researchers working in physiology, epidemiology, endocrinology, neuroendocrinology, neuroscience, and psychology.