1. Homeostasis P 334-340 Introduction to

2. Core Temperature Humans have a normal temperature of around 36.2 to 37.2 degrees Celsius Body temperature goes above normal temperature then likely suffering from an infection and your body had to raise its temperature to fight off the infection. If your body goes below this range it indicates hypothermia. Therefore if left untreated it could lead to cell damage and possibly death. http://asimplebutimpossibletask.blogspot.com/ http://news.bbc.co.uk/2/shared/spl/hi/health/03/travel _health/diseases/html/sars.stm

3. What is Homeostasis? The body’s attempt to maintain “normal” levels within your body Homeostasis is often referred to as a dynamic equilibrium- which is a mechanism to ensure that all body systems function within an acceptable range to sustain life. http://balancewines.wordpress.com/2009/12/

4. Homeostatic control systems 3 components: – Monitor – Coordinating centre – Regulator Monitor sends a signal to the coordinating centre that the normal levels have changed. The coordinating centre then messages the regulator which helps restore normal balance. Monitor Coordinating centre Regulator Normal balance Change in balance

5. Homeostasis Example: household thermostat Room temperature is set to 22 degrees Celsius. When the temperature falls below the “normal” temperature of 22 degrees, the thermostat recognizes change in “normal” temperature and switches on the furnace. When the thermometer detects a temperature above the “normal”, the thermostat switches off the furnace. http://gasfurnaceprices.co.cc/

6. Homeostasis Example: household thermostat Whole control system is called a negative feedback system Monitor- Thermometer Detects decrease in temperature Coordinating centre- Thermostat switches on furnace Regulator- Furnace Thermostat detects temperature increases over “normal” Furnace turns off

7. Negative feedback Process by which a mechanism is activated to restore conditions to their original state It ensures that small changes don’t become too large. Why is a thermostat a negative feedback system?

8. Negative Feedback Example: Thermoregulation The maintenance of body temperature within a range that enables cells to function efficiently – Heat Stress – Cold Stress

9. Negative Feedback Example: Thermoregulation Heat stress Thermoreceptors detect an increase in body temperature Hypothalamus signals to the sweat glands to initiate sweating. Evaporation of the sweat off the skin causes cooling. http://flairforthedramatic.mlblogs.com/archives/2008/09/of_all_times_to_start_w inning.html

10. Negative Feedback Example: Thermoregulation Heat Stress The hypothalamus also sends message to blood vessels in the skin causing them to dilate. Dilation allows for more blood flow to the skin. Heat from the blood is lost to the skin so blood can return to core of your body & cool the internal organs. http://www.pgbeautygroomingscience.com/functions- of-the-dermis.html

11. Negative Feedback Example: Thermoregulation Heat Stress Monitor: thermoreceptors Coordinating centre: hypothalamus turns on cooling system Regulator: skin blood vessels dilate and sweat glands initiate sweating Result: body temperature decreases; hypothalamus turns off cooling system

12. Negative Feedback Example: Thermoregulation Cold stress Thermoreceptors message the hypothalamus Hypothalamus sends a message via the nerves to: o Arterioles of the skin cause smooth muscles to contract, constricting arterioles & limiting blood flow =reduced heat loss from the skin and retains heat in the body. o Smooth muscle contract that surrounds the hair follicles in your skin causing the hair to “stand on end” trapping warm air. o Skeletal muscle to contract causing shivering and increasing your metabolism to make heat. http://www.clarian.org/ADAM/doc/HealthIllustratedE ncyclopedia/2/19194.htm

13. Negative Feedback Example: Thermoregulation Cold stress Monitor: Thermoreceptors Coordinating centre: Hypothalamus Regulator: skin blood vessels constrict and skeletal muscles contract Result: body temperature increases and hypothalamus turns off.

14. http://www.pgbeautygroomingscience.com/functions-of-the-dermis.html