1. Bellringer:

2. Today 9/17 Bellringer Summer Assignments Homeostasis Notes Homeostasis Worksheet & Activity Remember: I need WebQuests shared with me! sparkinson@rsd6.org

3. Maintaining Life Necessary Life functions – Internal things you need your body to do Survival Needs – External things you need for your body

4. Homeostasis (pg 8-12) The ability of the body to maintain a relatively constant internal environment, regardless of environmental changes

5. Components of Homeostasis: 1.Variable – Regulated factor or event 2.Receptor – Structure to monitor situation 3.Control Center – Structure that determines “set point” 4.Effector – Carries out response

6. Example: Homeostasis of Breathing Rate

7. How it works: As you accumulate CO 2 in your bloodstream, acidity of your blood increases Receptors in your carotid and aorta sense this, signal to medulla Medulla signals to diaphragm intercostal muscles- Breathing rate is now increased! CO 2 concentration lessened- acidity decreased

9. Afferent vs. Efferent Pathways Afferent Pathway – Signal from receptor to control center – A pproach control center Efferent Pathway – Signal from control center to effector – E xit control center

10. Negative Feedback Mechanism Most homeostatic control mechanisms are negative Prevent sudden, severe changes in the body Causes the variable to change in a way OPPOSITE the initial change Nervous System and Endocrine system

11. Positive Feedback Mechanisms Causes the variable to change in the SAME direction as the original change – ONE DIRECTION – AKA cascades

12. Positive Feedback Mechanisms (cont) Result is a greater change from set point Typically activate events that are self- perpetuating Usually not related to maintenance of homeostasis

13. Homeostatic Imbalance? DISEASE! – Examples Fever Hypertension Hashimoto’s disease Graves disease Kidney Malfunction Diarrhea

14. In class… Find an example of a way the human body maintains homeostasis (text book will help!) Identify the components What type of mechanism is it? What can happen if there is an imbalance of this homeostasis?