Feedback Mechanisms 1

HOMEOSTASIS

Homeostasis refers to stability, balance or equilibrium.
It is the body's attempt to maintain a constant internal environment.

Maintaining a stable internal environment requires constant monitoring and adjustments as conditions change. The adjustment of physiological systems within the body is called homeostatic regulation.

The homeostatic control has three components:
    I. A receptor (sense organ) to detect a change
    II. A center of control (the brain or the spinal cord) that will process and integrate what is happening
    III. An effector (muscle cells or organs/ glands) to produce a response appropriate to the change.

There are ways of communication among these components (basically through the nervous and endocrine control).

When a change of variable occurs, there are two main types of feedback to which the system reacts:

1. Negative feedback: a reaction in which the system responds in such a way as to reverse the direction of change.
    I. Thermoregulation
    II. Carbon dioxide concentration
    III. Blood sugar level

2. Positive feedback: a response is occurs to amplify the change in the variable. (This has a destabilizing effect, so does not result in homeostasis. Positive feedback is less common in naturally occurring systems than negative feedback, but it has its applications.)

    I. For example, in nerves, a threshold electric potential triggers the generation of a much larger action potential.
    II. Blood clotting
    III. Events in childbirth