1. Louis Chow

2. Homeostasis  The ability of the body to maintain a constant internal environment despite fluctuations in both the body’s activities and the external environment  Consists of specific values which are considered as normal What is it? Significance?  Enables organisms to explore inhospitable environments

3. Negative Feedback Mechanism...

4. Negative feedback mechanism 1.Receptors detects a stimulus (external or internal change). 2.Communication between the receptor and the effector(through a control centre). 3.Effector brings about the response to restore balance. 4.When the response is enough to return the body back to its normal state, the receptor is turned off.

5. Why control body temperature?  Independence from changing environments  Affects the rate of metabolic reactions  Sensitivity of enzymes

6. Ectotherms Ectotherms:  Fish, amphibians, reptiles etc.  Body temperature is greatly dependent on the external temperature  Variable metabolic rate  Activity levels determined by external environment

7. Behavioral responses  Voluntary responses  Temperature too cold: cuddling, put on more clothes, eating, more muscular activities, move closer to heat sources, e.g the Sun  Temperature too hot: Less clothing, cool drinks, find shades, body orientation

8. Endotherms Endotherms: Mammals and birds Mammals and birds Body temperature is less dependent on the external temperature Body temperature is less dependent on the external temperature High metabolic rate High metabolic rate Possess thermoregulating mechanisms Possess thermoregulating mechanisms

9. Physiological adaptions  controlled by the thermoregulatory centre in the hypothalamus.  Receptors in the hypothalamus itself(blood temperature, the core temperature)  Skin receptors (the external temperature)  Also controlled by the cerebral cortex -- Voluntary actions

11. Heat gain vs heat loss

12. Heat Exchange between organisms and their surroundings:

13. Core temperature and skin temperature http://www.youtube.com/watch?v=Vlp_NHuC0rw

14. Thermoregulation Hot:  decrease heat gain  Increase heat loss Cold:  Increase heat gain  decrease heat loss

17. Pilorelaxation and Piloerection Relaxation of erector muscle Contraction of erector muscle

18. Vasodilation and Vasoconstriction Hot:  Skin arterioles dilate  Sphincter muscles relax  Shunt vessels constrict  Blood flow to skin capillaries increased Cold:  Skin arterioles constrict  Sphincter muscles contract  Shunt vessels dilate  Blood flow to skin capillaries decreased

20. Sweat production Hot:  Activation of sweat glands  Increased sweat production Cold:  Inhibition of sweat glands  Decreased sweat production

21. Extreme temperatures Hypothermia  Core temperature falls below 35 degrees Celsius  Enhanced by alcoholic effects  Amnesia, death Hyperthermia  Core temperature higher than 38.5 degrees Celsius  Adverse effects by drugs  Heat stroke  Dizziness, confusion

22. Preventing hypothermia  Wear more clothes!!  Avoid diving in cold water  Go closer to heat sources

23. Preventing hyperthermia  Find shades  Avoid excess exercise

24. What might come in the exam..  Where is the best place to take a temperature of a person?  Define evaporative heat loss.  Describe and explain a way of losing heat.

25. THE END Thank you!