1. Biology in Focus, HSC Course Glenda Childrawi, Margaret Robson and Stephanie Hollis Maintaining a Balance Topic 3: Maintaining Homeostasis

2. DOT POINT Explain that homeostasis consists of two stages: Detecting changes from the stable state Counteracting changes from the stable state Gather, process and analyse information from secondary sources and use available evidence to develop a model of a feedback mechanism.

3. Negative Feedback Homeostasis involves an enormous amount of co-ordination and control in a living organism. In mammals, both the nervous system and endocrine (hormonal) systems are involved. Homeostasis is brought about in two stages: 1. Detecting Change 2. Counteracting Change infobarrel.com

4. Negative Feedback -Detecting Change: Sensory cells or receptors present within the body detect change in the temperature and/or chemical composition within the body. This change in the environment is called a stimulus. conservapedia.com

5. Negative Feedback -Counteracting Change: Effector organs (such as muscles or glands) then work to reverse the change. A response that successfully reverses the change will return the body to homeostasis. ehow.com

6. Negative Feedback Homeostatic mechanisms ensure that variables (such as temperature of the concentration of chemical substances) in the internal environment of an organism are maintained within a narrow range. Within each organism, these variables have an ideal of normal value, called the set point. comingbackalive.com

7. Negative Feedback If the fluctuation is large and exceeds the normal range, a negative feedback mechanism comes into operation in response to this change. It is termed negative because it counteracts the change (stimulus), returning the body to within the normal range: to a state of homeostasis. 3abhbs.blogspot.com

8. Negative Feedback bio233notes.blogspot.com

9. Activity -Students are to complete Activity 1.3.1 Negative Feedback