1. H OMEOSTASIS Homeostasis is the body’s ability to keep the internal balance of the body stable.

2. TEKS 13A: The student will investigate how organisms respond to external stimuli found in the environment such as phototropism and fight or flight. TEKS 13B: The student will describe and relate responses in organisms that may result from internal stimuli such as wilting in plants and fever or vomiting in animals that allow them to maintain balance.

3. Endocrine Testosterone, estrogen, human growth hormone, insulin

4. Write the information in your notebook.

5. 1. How will a person know if he/she has high or low blood sugar? (what are symptoms, signs from the body) 2. What is the body’s response to unstable blood sugar? (what is happening internally, inside the body) 3. How can the body stabilize the blood sugar? http://diabetes.about.com/od/symptomsdiagnosis/p/Symptoms.htm http://www.thebody.com/content/art12776.html Hyperglycemia is part of Diabetes.

6. Think: So, what is a definition of “feedback mechanism”? The control of blood sugar (glucose) by insulin is another good example of a negative feedback mechanism. When blood sugar rises, receptors in the body sense a change. In turn, the control center (pancreas) secretes insulin into the blood effectively lowering blood sugar levels. Once blood sugar levels reach homeostasis, the pancreas stops releasing insulin. Another good example of a negative feedback mechanism is a home thermostat (heating system). The thermostat contains the receptor (thermometer) and control center. If the heating system is set at 70 degrees Fahrenheit, the heat (effector) is turned on if the temperature drops below 70 degrees Fahrenheit. After the heater heats the house to 70 degrees Fahrenheit, it shuts off effectively maintaining the ideal temperature.

7. Another good example of a positive feedback mechanism is blood clotting. Once a vessel is damaged, platelets start to cling to the injured site and release chemicals that attract more platelets. The platelets continue to pile up and release chemicals until a clot is formed.

8. 2. Stimulus is anything to which an organism may respond. 4. & 5. A stimulus may be something outside of the organisms’ body (external stimulus) or something within the body (internal stimulus). 3. A response is an action taken to maintain balance in a system. 6. Fight or flight is an internal feedback system designed to increase survival of an organism. 7. An organisms body always wants to keep running in a stable or balanced manner. Keeping system stability increases survival.

9. http://www.youtube.com/watch?v=zctM_TWg5I k

10. Watch your teacher set up and explain the Response Laboratory Investigation using the Pill Bugs. Pay attention. You will write in your laboratory notebook the investigation using the 8 steps of Scientific Investigation. LOOK in your notebook or on the board to remember the steps. Problem: 1.How do animals respond to stimuli? 2.Why did the pill bugs move to a particular quadrant of the pan?