1. Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. Homeostasis Negative feedback systems in the human body

2. What does the word “feedback” mean? Example: Students receiving progress reports What is the purpose? What is an acceptable range? What happens when you fall out of that range?

3. Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. What is homeostasis? Process that occurs in all living things All organ systems work together to achieve homeostasis Definition: http://en.wikipedia.org/wiki/File:Tightrope_artist_Cologne_1.jpg

4. Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. How does homeostasis work? Feedback pathways A cellular relay race! Specific organs and structures must communicate with each other in response to changes in the body Keeps levels within “normal” range http://en.wikipedia.org/wiki/File:Southern_12_stage-02_1988.jpg

5. Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. What things in your body need to be kept within a range? Body Temperature Body Temperature Blood pressure Blood pressure Blood pH Blood pH O 2 and CO 2 concentration O 2 and CO 2 concentration Osmoregulation-Water balance Osmoregulation-Water balance Blood glucose Blood glucose

6. Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. Cellular Relay Race Stimulus Receptor Integrating center Effector Response Reverses the stimulus

7. Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. Negative Feedback Pathways Way in which most homeostatic mechanisms work The product of the pathway inhibits, or shuts down, the original signal Why is this an important feature in living things?

8. Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. Why is feedback important in living things?

9. Distribute Feedback Activity Handout Blood Glucose Animation: http://outreach.mcb.harvard.edu/materials.ht m http://outreach.mcb.harvard.edu/materials.ht m Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.

10. Dueling Hormones What goes up, must come down! Insulin  Produced by _____of the Pancreas  Released into circulatory system when blood glucose is ________  Facilitates the _________________ _________________ Glucagon  Produced by _____of the pancreas  Released into the circulatory system when blood glucose is ___________  Signals the liver to _________________ _________________

11. Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. Dueling Mechanisms What goes up, must come down! Thermoregulation Sweating (cooling) vs. shivering (warming) Blood Pressure Vasconstriction vs. vasodilation Osmoregulation Hypotonic vs. hypertonic

12. Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College. Food for thought… On average, how many organ systems are involved in each of the processes we’ve explored? On average, how many organ systems are involved in each of the processes we’ve explored? Are there any organ systems that you see in all of these processes? Are there any organ systems that you see in all of these processes? What might happen to these pathways if just one system was not functioning properly? What might happen to these pathways if just one system was not functioning properly?