To figure out how living organisms work, including the physical and chemical processes that take place in living organisms during the performance of life functions. Physiology investigates biological mechanisms with the tools of physics and chemistry. It is closely related to anatomy, though physiologists focus on bodily functions; anatomists on bodily structures. General physiologists focus on the basic functions common to all life. Physiologists may focus on particular life forms, pathology, or comparative studies. (Plant physiology, a branch of botany, focuses on the life functions within plants.)

What are the basic functions common to all life? What physical and chemical processes take place in living organisms during the performance of life functions? What happens in a body during reproduction, growth, metabolism, respiration, digestion, excitation, and contraction? What happens during these functions within the bodies’ cells, tissues, organs, or within organ or nerve systems? In what ways can life functions be disrupted, injured, or diseased?

The main information obtained by physiologists is from the direct study of physical and chemical processes as these take place in living organisms during the performance of life functions. They observe cells, tissue, and organs microscopically. They observe them in artificial and real-life environments. They compare structures and functions of life processes.

Physiologists make judgments about functions common to all life forms as well as differences among them. They judge how these functions best perform and thrive. They make judgments about pathologies and interpret how internal systems and functions interrelate with environment realities.

The most fundamental concept in physiology is the concept of bodily functions in systemic relations. Other important concepts used to guide physiological thinking are: reproduction, growth, metabolism, respiration, blood circulation, nutrition, digestion, excretion, excitation, contraction, cells, tissues, nerves, muscles, bones, organs, systems of organs, organ and system pathology.

Physiologists make the following assumptions:

1) living things must perform a specifiable group of common and essential functions;

2) different species of living things perform various common functions in different and sometimes unique ways (through diverse cell, tissue, and organ structures); and,

3) it is possible for physiologists to accurately describe, test, and verify their descriptions and theories concerning functions performed within animal systems.

The implications of human physiology are interconnected with those of bacteriology, immunology, chemistry, and physics, among other scientific branches. Physiologists who study animal functions have made numerous discoveries about bodily functions (such as the heart, brain,and other organs) which have led to advancements in medical treatment. The implications for medical care, for human and veterinary medicine, through physiological study, are virtually unlimited.

Physiologists see life functions as systems working harmoniously to perform essential processes. They also see pathology within living systems as a breakdown in this harmonious process which, when studied, can lead to less pathology and improved life quality.