Physiology

Physiology is the science of how living organisms function, from the smallest forms of life to multicellular organisms such as plants or animals. Since function is obligatorily coupled to structure. This interrelationship presents a principal focus at all levels of biological organization. Approaches that stem from physics and chemistry provide the format for analysis of cellular and subcellular processes in the service of function. Thus were general physiology may search for fundamental processes that may be common to all cells, comparative physiology and mammalian physiology define the functioning of different systems and different organisms at varying levels of complexity.

Principles that apply at one level have counterparts at another; for instance, understanding the mechanisms that govern the flow of electrical current across cell membranes underlies the basis for electrical signaling in the nervous system. Claude Bernard formulated the principle of the constancy of the internal environment (called homeostasis) that is illustrated by such integrated and controlled activities as the adaptive responses of respiratory, contractile, and hormonal systems and in the set-points of blood pressure and body temperature. While it is clear that analysis of functional activity at the cellular and subcellular level is becoming increasingly more quantitative and molecular, it is also evident that there are functions that are only understandable at the integrated or whole animal level, such as perception, consciousness, or exercise.

Physiology deals with the experimental analysis of normal processes in normal systems in contrast to pathophysiology that subserves medicine as attended by injury and disease. There is a clear reciprocity of fundamental insight that emerges from comparisons of normal and abnormal processes. The study of physiology lends an understanding of life processes and provides us with profound opportunities to fulfill the precept “Think of all, hold on to the beautiful.”

Joseph F. Hoffman

Higgins Professor of Cellular and Molecular Biology

Yale University School of medicine