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Louis Chow

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Louis Chow

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  1. HOMEOSTASIS Thermoregulation Louis Chow

  2. What is it? Significance? Enables organisms to explore inhospitable environments 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

  3. Negative Feedback Mechanism...

  4. Negative feedback mechanism • Receptors detects a stimulus (external or internal change). • Communication between the receptor and the effector(through a control centre). • Effector brings about the response to restore balance. • 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 • Body temperature is less dependent on the external temperature • High metabolic rate • 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

  10. Heat gain vs heat loss

  11. Heat Exchange between organisms and their surroundings:

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

  13. Thermoregulation Hot: Cold: Increase heat gain decrease heat loss • decrease heat gain • Increase heat loss

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

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

  16. Sweat production Hot: Cold: Inhibition of sweat glands Decreased sweat production • Activation of sweat glands • Increased sweat production

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

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

  19. Preventing hyperthermia • Find shades • Avoid excess exercise

  20. 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.

  21. THE END Thank you!