1. Give me some Feedback!

2. 2 Homeostasis* * Maintaining of a stable internal environment Homeostatic Control Mechanisms – monitors aspects of the internal environment and corrects as needed. Variations are within limits. There are three (3) parts: Receptor - provides information about the stimuli Control Center - tells what a particular value should be (called the set point) Effector - elicits responses that change conditions in the internal environment

3. Homeostatic Control Mechanisms Stimulus (Change occurs in internal environment.) Response (Change is corrected.) Receptors Effectors (muscles or glands) Control center (set point) (Change is compared to the set point.) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3

4. 4 Homeostatic Control Mechanisms Receptors Thermoreceptors send signals to the control center. too high too low Normal body temperature 37°C (98.6°F) Control center The hypothalamus detects the deviation from the set point and signals effector organs. Control center The hypothalamus detects the deviation from the set point and signals effector organs. If body temperature continues to drop, control center signals muscles to contract Involuntarily. Stimulus Body temperature rises above normal. Effectors Skin blood vessels dilate and sweat glands secrete. Response Body heat is lost to surroundings, temperature drops toward normal. Receptors Thermoreceptors send signals to the control center. Effectors Skin blood vessels constrict and sweat glands remain inactive. Stimulus Body temperature drops below normal. Effectors Muscle activity generates body heat. Response Body heat is conserved, temperature rises toward normal. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

5. 5 There are two (2) types: Negative feedback mechanisms Positive feedback mechanisms Homeostatic Control Mechanisms

6. 6 Negative feedback summary: Prevents sudden, severe changes in the body Corrects the set point Causes opposite of bodily disruption to occur, i.e. the ‘negative’ Most common type of feedback loop Examples: body temperature, blood pressure & glucose regulation Homeostatic Control Mechanisms

7. 7 Positive feedback summary: Increases (accelerates) the actions of the body short-lived do not require continuous adjustments Produces more instability and chaos in the body Controls only infrequent events that do not require continuous adjustments. Examples: blood clotting and child birth Homeostatic Control Mechanisms

8. 8 Animation: Positive and Negative Feedback Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.