1. Chapter 7 - Maintaining an Internal Balance 7.1 & 7.2

2. Homeostasis human body systems are constantly adjusting to changes in the external environment to maintain a constant internal environment homeostasis is an active process, sometimes called dynamic equilibrium

3. Optimal Human Body (Image from: http://www.liesyoungwomenbelieve.com/index.php?id=354) temperature: 37ºC blood sugar level: 0.1% blood pH: 7.35 etc.

4. Homeostatic Control System (Image from: http://www.revisescience.co.uk/2010/schools/ilford/abhomeostasis.asp) monitor coordinating center regulator

5. Feedback Systems negative feedback –signals coordinating centre to counteract any detected changes in the same direction –prevents a small change from becoming too large

6. Negative Feedback (Image from: http://www.freewebs.com/sandra02n/)

7. Negative Feedback (Image from: http://academic.kellogg.edu/herbrandsonc/bio201_mckinley/endocrine%20system.htm)

8. Feedback Systems (Image from: http://ingrimayne.com/econ/AllocatingRationing/PriceAndFeedback.html) positive feedback –signals coordinating centre to amplify any detected changes in the same direction –much less common –causes a small change to become larger

9. Positive Feedback (Image from: http://pespmc1.vub.ac.be/feedback.html)

10. Positive Feedback (Image from: http://biologyfiles.fieldofscience.com/2011_01_01_archive.html)

11. Thermoregulation the regulation of body temperature each species has an optimal temperature

12. Thermoregulation ectotherms temperature is regulated by external temperature endotherms can maintain constant body temperature regardless of external changes

13. Ectotherms & Endotherms (Image from: http://faculty.uca.edu/johnc/animalstructfu.htm)

14. Thermoregulation (Image on next slide from: http://schoolworkhelper.net/2010/07/thermoregulation/) In humans, the hypothalamus (part of the brain) is the coordinating centre for thermoregulation. Image taken from: http://zaborina.i.ph/photo/108/109

16. Mammalian Diving Reflex when a mammal is submerged in cold water, the hypothalamus signals –the heart rate to slow down –blood to be diverted to the brain and other vital organs to conserve heat useful in preventing hypothermia

17. Mammalian Diving Reflex (Image from: http://www.celticseakayaking.com/articles/mammal.htm)