2. HOMEOSTASIS An organism’s ability to maintain a constant, stable internal environment. Pgs6-12

3. HOMEOSTATIC MECHANISMS Operate by the interaction of 3 components:  Receptors-sensitive to stimuli  Control Center-receives & processes information  Effectors-cell or organ that responds

4. FEEDBACK MECHANISM EXAMPLES http://www.bbc.co.uk/schools/gcsebitesize/science/add_aq a_pre_2011/homeo/homeosts.shtml http://www.bbc.co.uk/schools/gcsebitesize/science/add_aq a_pre_2011/homeo/homeosts.shtml http://www.youtube.com/watch?v=CLv3SkF_Eag Book Animation

5. HOMEOSTATIC MECHANISMS Classified as: Negative Feedback Mechanisms or Positive Feedback Mechanisms

6. NEGATIVE FEEDBACK MECHANISMS Operate to bring the internal environment back to the homeostatic, or normal, state They work in such a way that they negate, or oppose the change that has occurred from the normal, homeostatic state They slow or stop a process Examples; regulation of body temperature, blood sugar, blood oxygen level, heart rate, respiration rate, and pH levels in the stomach http://www.pennmedicine.org/health_info/diabetes2/000272.html

7. POSITIVE FEEDBACK MECHANISMS Operate to increase the deviation from the normal, homeostatic state Usually only operate in specific situations and for short periods of time They speed up a process Examples; blood clotting process, the labor process, and many enzymatic reactions