1. Day Objective: Define homeostasis and its affect on human body systems. Describe the role of the cell membrane in maintaining homeostasis. Warm up: Which macromolecule is the main component of cell membranes?

2. 1. Homeostasis A. Maintaining a steady state or “state of balance” B. Think back to yesterday and “Ben’s Bad Day.” In what ways does the human body maintain homeostasis?

3. 2. B. How does homeostasis work? Mechanisms that allow regulation of a steady internal environment even though the outside environment is changing. B. Example: Dogs pant on a hot day…..

4. 3. Homeostatic control system 3 components 1. receptor * function: detect change of the internal environment 2. control center * function: receives and processes information from receptor and directs a response 3. effector * function: carries out the response

5. 4. Example of Homeostatic control system How is room temperature controlled? When the room temperature falls below a set point, like 65 degrees, the thermostat switches on the heater (the effector).

6. 5. Negative Feedback Example : Thermostatic Control System Receptor: thermometer Control center: thermostat Effector: Heater The change in the environment triggers an effector to counteract the change.

7. 6. Positive Feedback Involves a change that triggers mechanisms that amplify rather than reverse the change (negative feedback) Example: Childbirth, the hormones increase.

8. Negative Feedback  In a negative feedback system some factor, such as blood pressure, changes.  The change is detected by a sensor or receptor.  The sensor sends a message to a control center which in turn stimulates an effector.  The effector will do something to alter the factor that changed.

9. Blood pressure has increased!  Receptors in the carotid arteries detect the change in blood pressure and send a message to the brain  The brain (control center) will cause the heart (effector) to beat slower and decrease the blood pressure.  Decreasing heart rate has a negative effect on blood pressure.

10.  After we eat the level of glucose increases in the blood.  Receptors in the pancreas respond to the increased blood sugar.  The pancreas also functions as an integrating center and effector. It secretes insulin which helps glucose enter cells and thus reduce the blood glucose level.

11. Homeostasis Interactive Go to the following website and go through the does Ben have diabetes? http://ats.doit.wisc.edu/biology/ap/ho/ho.htm http://ats.doit.wisc.edu/biology/ap/ho/ho.htm Complete the worksheet you picked up today as you go through Ben’s day!