1. Homeostasis and Feedback

2. Homeo = Similar Stasis = State Definition: Maintaining a stable internal environment within a narrow range - keeps proper function of enzymes for metabolic processes Involves all organ systems!

3. What needs to be regulated? (Only need to write what is in bold) Nutrients – oxygen, glucose, proteins etc. Electrolytes – salts (muscle contractions nerve transmission) Waste concentrations – CO 2, urea (nitrogen wastes), bile pH Temperature Pressure/volume – gases in blood, lungs

4. Video Homeostasis http://www.bbc.co.uk/schools/gcsebitesize/scie nce/add_aqa_pre_2011/homeo/homeosts.shtm l

5. How to regulate (top chart left side) Set point – what is the desired range? Sensors – structures including receptors on target cells that will monitor levels relative to set point Controller – determine if levels are within set point range and what response is necessary to return to range Effector – parts of body that physically make the change to return to set point range

7. Negative Feedback (write in comparing -/+ space below chart) change from the normal range is opposed (thus negative) brings it back within optimal range and decreases the chaos in the body Most systems in body are negative feedback Examples – body temperature, blood sugar

8. Thermostat Analogy

9. Body Temperature (right side of chart) Set Point: 98.6 degrees F (37 degrees C) Sensors: sensory nerves Controller: hypothalamus area in brain sends signals to muscles via nerves Effector: muscles, sweat, blood vessels (hot/cold details on next slide)

10. Effectors:

11. EX. Body Temperature Effectors When Cold (don’t need to copy this) Muscles/circulatory constrict peripheral blood flow body sacrifices fingers and toes to save your internal organs Muscles at follicles raise hairs (goose bumps), Skeletal muscles contract (shiver) generate heat Heart rate slows to keep blood concentrated in core body Skeletal muscle adjust body curls up fetal position

12. Positive feedback (write in comparison space under chart) Reinforces the original stimulus – pushing conditions further from the normal Less common as it can get out of control and will not stop until stimulus is removed (the bleeding stops) Increases chaos in body systems Examples – blood clotting and child birth

13. Clotting signals continue until clot is complete and bleeding stops

14. Next Steps 1. Read blood sugar article individually 2. Answer the 9 questions at the end of the article on the BACK of the graphic organizer page OR write on separate paper to staple to the graphic organizer 3.Complete the bottom chart on the graphic organizer (challenging) turn in at end of class 4.Complete Osmosis and Diffusion Practice Due Tuesday