What is homeostasis?

Homeostasis is the maintenance of a relatively stable internal environment.

Organisms are able to detect changes that could disrupt their stable internal environment.

The change that the animal detects is called a stimulus
The part of the organism that detects the change is called the receptor
Information about the stimulus can be processed by a control centre (brain), which coordinates a response
The part of the organism which causes the response is called the effector

Stimulus-Response Model

Stimulus -> Receptor -> Control Center -> Effector -> Response

example: Cold Temperatue -> Skin -> Brain-> Muscles -> Shivering

example: Hot Temperature -> Skin -> Brain -> Sweat Glands -> Sweating

Positive and Negative Feedback Loops

A negative feedback loop produces a response that is opposite to the stimulus.

A positive feedback loop produces a response that is the same as the stimulus.

Introduction