Medical Physiology is a field of science wherein the various systems of the body are studied from a molecular level, upto the integrated functioning of the human body. Essentially, physiology is the gateway to clinical medicine. With advances in research, the subject has expanded tremendously. Despite volumes of information being available, students are perennially perplexed by the seemingly insurmountable nature of the subject. During my vast experience in teaching, I have found students facing particular difficulty tackling the questions marked ?Explain why?, presumably because merely memorising the topics will not suffice; concepts have to be understood. Many of my students have, in the past, requested me to write a book on the explanatory notes, which are a part and parcel of the question papers. Thus, my intention was not to write a textbook as many are already available. The purpose of this ?one-of-a-kind? book is to serve as an essential resource for students by providing comprehensive, yet concise and user-friendly material that will help undergraduate and post-graduate students alike in clearing their doubts and strengthening their basics. I have listed the questions from the past 20 years of question papers and have also made my own additions. The entire subject has been divided into 11 chapters based on the various systems of the body. The definitions are written in blue and the explanations are in red. Numerous illustrations and flow diagrams have been provided for rapid reference and assimilation. It will be of very help for answering the viva as well.