To stay alive the cells of an organism need proper nutrients, oxygen and it’s metabolic waste must be removed. This goal affects the organism’s interactions with its environment.

The component parts of any organism (whether it is one-celled or a human being) must work together to maintain a stable fluid environment that all of its cells require. There must be a relative consistency (a controlled sameness) of the organisms internal environment. This is the basic concept of Homeostasis.

Multicellular organisms must regulate their internal environment. Maintenance of a stable internal environment is critical to the well-being of an organism; regulatory mechanisms must be carefully controlled.

It is important that an organism keep its chemical processes occurring at the correct rate and time.

When living things are able to regulate these chemical processes precisely, they can maintain a stable internal environment.

HOMEOSTATIC CONTROL mechanisms help maintain, both physical and chemical aspects of an organisms internal environment within ranges that are favorable for cells to function.

1. SENSORY RECEPTORS: Cells that can detect stimulus (a change in the environment).
2. INTEGRATOR: The BRAIN processes the information about the stimulus and selects a response.
3. EFFECTORS: Carry out the response to the stimulus (MUSCLES&/or GLANDS)

FEEDBACK MECHANISMS are the controls that operate to keep chemical and physical aspects of the body within tolerable ranges.

A VARIABLE in the environment triggers the mechanism. A variable triggers change.

A POSITIVE FEEDBACK mechanism amplifies positive change.

in a NEGATIVE FEEDBACK mechanism, something alters the condition in the internal environment, and this triggers a response to reverse the altered condition.

Homeostasis is dependent upon positive or negative feedback mechanisms.