The document summarizes key concepts in human physiology: - Physiology is the study of how living organisms function through physics, chemistry and anatomy. The basic functional unit is the cell. - The body contains systems like circulatory, respiratory and nervous systems that work together. Cells combine to form tissues and tissues form organs. - The cell membrane regulates what passes in and out using diffusion, channels, carriers and pumps. It separates intracellular fluid from extracellular fluid in the body.