Physiology and Maintenance is a component of Encyclopedia of Biological, Physiological and Health Sciences in the global Encyclopedia of Life Support Systems (EOLSS), which is an integrated compendium of twenty one Encyclopedias. The Theme on Physiology and Maintenance with contributions from distinguished experts in the field, discusses the functions of our body and their regulations which are some of the most fascinating areas of science. The content of the theme is organized with state-of-the-art presentations covering the following aspects of the subject: General Physiology; Enzymes: The Biological Catalysts of Life; Nutrition and Digestion; Renal Excretion; Endocrinology; Respiration; Blood Circulation: Its Dynamics And Physiological Control; Locomotion in Sedentary Societies; Neurophysiology; Plant Physiology and Environment : A Synopsis, which are then expanded into multiple subtopics, each as a chapter. These five volumes are aimed at the following five major target audiences: University and College students Educators, Professional practitioners, Research personnel and Policy analysts, managers, and decision makers and NGOs.