The study of the functions of the body's systems is called physiology. This field examines how various organs and systems work together to maintain overall health and respond to changes in the environment. Physiology encompasses various subspecialties, including cardiovascular physiology, neurophysiology, and respiratory physiology, emphasizing the interconnectedness of bodily functions. Understanding physiology is crucial in medicine, as it provides insight into normal body functions and how they may be altered in disease states, guiding effective diagnosis and treatment options.