The physiology of adaptive change

It has been recognized for a long time that the function of various neuroendocrine and physiological systems does not conform to the classic principal of homeostasis. The formulation of the ‘fight or flight’ reactions and the general adaptation syndrome by Cannon and Selye have provided an intellectual framework for considering many of these systems in the context of acute and chronic tissue-level responses to changing external challenges, and not as a part of the integrated normative adaptive biology that maintains the viability of the whole organism [1xBodily changes in pain, hunger, fear and rage. Cannon, W.B. See all References, 2xThe wisdom of the body. Cannon, W.B. See all References, 3xThe stress of life. Selye, H. See all References]. Sterling and Eyre [4xAllostasis: a new paradigm to explain arousal pathology. Sterling, P. and Eyre, J. : 629–649See all References][4] proposed and developed the concept of allostasis, literally ‘achieving stability through change’, to provide a logical structure for understanding these ever-shifting integrated systems that promote adaptation and drive natural selection. This concept is the unifying theme of the ten essays in Allostasis, Homeostasis, and the Costs of Physiological Adaptation. However, the perspectives of each chapter vary and there are sometimes subtle differences in how the chapter authors interpret a concept. Thus, rather than being a definitive guide to how allostasis operates, this is a deeply thoughtful, engrossing and provocative compilation of discussions of an emerging and evolving paradigm in behavioral neuroscience, neuroendocrinology and physiology.Because allostasis is an integrative process, it has ramifications for all aspects of behavioral neuroscience, regulatory physiology and systemic chronic disease pathology, whether considered in humans or other species. Hence, the topics covered in this volume vary widely, although they are not exhaustive of the literature in either regulatory physiology or behavioral neuroscience. Different essays explore how allostasis might operate in conjunction with homeostats (negative feedback systems that buffer the effects of stress); drug addiction and feed-forward mechanisms; chronobiological rhythms (ultradian, circadian, menstrual, seasonal and annual); adaptive and maladaptive fear and anxiety; lifecycle variation (relating to physiological changes during puberty, pregnancy and aging in humans and non-human species); and chronic disease development and pathophysiology. In describing the pathological processes and mechanisms associated with allostasis, other terms are introduced: allostatic state, defined as ‘…chronic overactivation of the regulatory systems and the alterations of body set points…’; allostatic load, defined as ‘…the cost to the body of adapting repeatedly to demands placed upon it…’; and allostatic overload, defined as ‘…the expression of pathophysiology by the chronic overactivation of regulating systems…’. These terms provide necessary conceptualizations for developing and describing methods for measuring pathophysiological processes.After digesting the essays in this book, it became apparent that what makes allostasis a potentially powerful concept is that it unifies the physiology of acute and long-term adaptations and stress responses as well as their outcomes into a single integrated process. Other concepts that are discussed throughout the book, such as rheostasis, homeorhesis and predictive homeostasis, although useful in describing physiological processes with varying set points, and which overlap conceptually to varying degrees with allostasis, do not really unify theories of behavior, physiology and pathophysiology.In addition to the theoretical aspect of Allostasis, Homeostasis, and the Costs of Physiological Adaptation, there is a wealth of well referenced and illustrated information in each chapter about the regulatory physiological mechanisms and processes of the systems that undergo allostasis. Several authors also provide a historical perspective, including references to the seminal works of Bernard, Cannon and Selye [1xBodily changes in pain, hunger, fear and rage. Cannon, W.B. See all References, 2xThe wisdom of the body. Cannon, W.B. See all References, 3xThe stress of life. Selye, H. See all References, 5xSee all References]. There is a particular focus on the brain and its processes; there are beautifully detailed and well articulated discussions of the workings of the hypothalamus, amygdala, hypothalamic–pituitary–adrenal and sympathetic–adrenal axes, cardiovascular regulation and circadian oscillators. In fact, the depth and breadth of the discussions of neurobiology, neuroendocrinology and physiology alone would make this volume a worthwhile read, even without the perspective of allostasis.It is rare to read an edited volume where there is strength in every chapter but that is the case here. Allostasis, Homeostasis, and the Costs of Physiological Adaptation is so full of ideas that it will be a welcome addition to the library of anyone who has wrestled with the biology and psychology of stress and adaptation. If you have never heard of allostasis, then this is an excellent volume to introduce you to the topic. From an academic perspective, this book would be an excellent text for a graduate interdisciplinary course on stress and disease. Finally, and most importantly, perhaps the best thing about the book is that it really makes the reader think.