Medicine is an ever changing science. Physiology is one of the main foundations of medicine and involves interacting and interdependent processes at the level of cells, tissues, organ systems, and at the level of a body as a whole. The first chapter of the book, thus begins with highly simplified presentation of the overall view of mammalian and particularly human physiology. This is followed by general physiology principals that make the basis of interrelation between the various systems that characterize physiology. Particular attention has been paid to cellular physiology, cardiac electrophysiology, neural and chemical control of respiration, renal mechanisms, and skeletal muscle physiology, Peripheral and central neurophysiological functions are presented with the details of neural pathways and their role. Special senses and the autonomic nervous system and the account of gastrointestinal tract and nutrition are properly covered. Endocrinology is described with mechanisms of hormonal action. The chapter on reproduction not only relates to the hormonal changes but also provides an account of maternal and fetal physiology. The book is an authentic text for undergraduate and the postgraduate students of medicine as well as for the students of allied sciences.