Human physiology

Academic and non-academic biologists study human physiology to understand the workings of the human body and its component parts, at one or more levels of the human body’s organization.

By workings, physiologists refer to the underlying mechanisms that operate to manifest themselves in observable properties, functions and behaviors of the body and its components (e.g., sweating, digestion, muscle contraction, vision, cell division). By one or more levels of organization physiologists refer to such levels of organization as the fundamental chemical level, intracellular molecular networks, cellular activity, organ activity, inter-organ interactions, and whole-body behavior — always in relation to a level's environment. At any level of the body's organization, elucidating the operative underlying mechanisms may require integrating principles and information from other disciplines, including chemistry, physics, mathematics, computer modeling, cybernetics, nutritional science, systems biology, evolutionary biology, and many others.

A human physiologist might ask, for example:

• How does the body respond to large or small decreases or increases in ambient temperature;
  • which of its component parts participate in the response;
  • in what way do they participate;
  • what accounts for the mechanisms that operate in each individual component response;
  • how does the overall response become integrated;
  • How important is the response to the person's health;
  • how efficient and how effective is the response.

The description of the human body’s complicated coordinated response to an unusually hot or cold day, and many other perturbations from outside or inside the body, do not admit of simplistic accounts — i.e., accounts sufficient to fully explain the response, predict its properties, or control it.

Whereas physiologists aim to learn the workings of the body in its state of health — i.e., to learn normal physiological function — they often gain insights into normal physiological function by studying the physiological effects of disease states, i.e., studying pathophysiology.

This article will describe the major subsystems that comprise the components of the living human system and attempt to show how those subsystems interact in a coordinated way that contributes to the emergence and maintenance of the living system.