Human physiology

Professional and non-professional 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’ they 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).

They 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; and,
• how does the overall response become integrated.

By “one or more levels of organization” they refer to such levels of organization as molecular networks, cellular activity, organ activity, inter-organ interactions, and whole-body behavior in relation to a level's environment.

The complexity of the human body’s coordinated response to an unusually hot or cold day does not admit of a simplistic account — i.e., an account sufficient to explain the response, predict its properties, or control it.

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 of the living system.