Physiological activity refers to the normal function of an organism. It may refer to specific organs or the organism as a whole.
The act of a human eating, sleeping or even thinking is considered a physiological activity. Generally, physiology breaks into ten distinct systems that are essential to the human body's survival and function. These include the cardiovascular, nervous, digestive, endocrine, immune, muscular, renal, reproductive, respiratory and skeletal systems.
Homeostasis, or the body's ability to regulate itself no matter the environment, is the cornerstone of physiology. It is the function that drives activity for each of the systems within the body as each of the systems works solo or in conjunction with other systems to optimize health.