Physiology

What is it?

According to NCI SEER, body functions are defined as the physiological or psychological functions of the body's systems.

The material states that the body's primary goal is survival, which depends on maintaining homeostasis: "a state of relative constancy" of the internal environment. It clarifies that it "does not mean something rigid and fixed that stays the same all the time".

MedlinePlus Genetics states that cells are the basic building blocks of all living things, and that the human body is made of trillions of cells that build the body's structure, take in nutrients and convert them to energy, and perform specialised functions. The source page did not address how cells come together into tissues and organs.

Why is it done?

SEER explains that the activities that make survival possible include responding to changes in the environment, exchanging materials with cells, metabolising food, and coordinating the body's various activities.

The body is built from graded levels: cells, then tissues, then organs, then systems, working together "in an organised way" (SEER).

Key points

**The ten life processes according to SEER:** organisation (division of labour at all levels, and its loss leads to cell death), metabolism (all the chemical reactions in the body), responsiveness (sensing and reacting to changes in the environment), movement (at the level of molecules, circulation and muscles), reproduction (forming a new organism and replacing cells), growth (by increasing cell number or size), differentiation (non-specialised cells becoming specialised), respiration (exchange of oxygen and carbon dioxide between cells and the external environment), digestion (breaking down complex foods into absorbable molecules), excretion (removing the waste products of metabolism).

These processes need support from the environment: water, oxygen, nutrients, heat and pressure (SEER).

The ten systems listed by SEER: skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, reproductive.

Limits of the test

The source of this page is introductory educational material from NCI SEER; it does not cover the fine regulatory mechanisms (such as feedback), normal values or diseases. For normal values, see your laboratory report and your doctor's interpretation.

Common questions