Human physiology is the study of how the body functions and the processes that keep it alive. It examines various systems, such as the circulatory system, which transports blood and nutrients, and the nervous system, which controls responses to stimuli. Understanding these systems helps us learn how organs work together to maintain health. Additionally, human physiology explores how the body responds to different conditions, such as exercise or illness. For example, during physical activity, the muscular system works harder, and the respiratory system increases oxygen intake. This knowledge is essential for fields like medicine and sports science.