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Thermoregulation & Feedback How do different organisms maintain temperature balance? Warm-blooded (endotherms) Cold-blooded (ectotherms)

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Presentation on theme: "Thermoregulation & Feedback How do different organisms maintain temperature balance? Warm-blooded (endotherms) Cold-blooded (ectotherms)"— Presentation transcript:

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2 Thermoregulation & Feedback How do different organisms maintain temperature balance? Warm-blooded (endotherms) Cold-blooded (ectotherms)

3 Temp Regulation - Homeostasis Why must organisms maintain internal temp balance? Enzymes!!  Enzymes speed up chemical rxns in your body  Enzymes only work under certain conditions

4 Thermostat Temperature set on thermostat Too cool? Heater kicks on and temperature goes up Too warm? Stays off until house cools down Constant checking and turning on and off

5 Control of homeostasis through feedback Feedback system- cycle of events in which the status of a body condition is continually monitored, evaluated, changed, re- monitored, re-evaluated, etc.

6 1) receptor  sensor that responds to changes (stimuli) 2) control center  sets range of values, evaluates input and sends output 3) effector  receives output from control center and produces a response 3 basic components of a feedback system

7 Body Temperature Control The hypothalamus acts as a thermostat and receives nerve impulses from heat and cold thermoreceptors in the skin. There are also receptors in the hypothalamus- called central thermoreceptors. These detect changes in blood temperature.

8 Summary What is the difference between an ectotherm and an endotherm? What are the components of a feedback system?

9 Maintenance of Body Temperature

10 Epidermis Dermis Outermost layer Middle layer Innermost layer Sweat gland Blood capillaries Subcutaneous fat Receptors Erector muscle Nerve fibres Sebaceous gland Hair follicle Structure of Mammalian Skin

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12 Vasoconstriction and Vasodilatation

13 Correction of overheating 1. Detected by thermoreceptors in the hypothalamus. 2. Causes vasodilation. 3. Sweating

14 Sweating How does it work? Heat energy in the body is used to convert the water in sweat to vapour cooling down the body.

15 Heat Loss Radiation: Transfer of heat via infrared rays  60% heat loss at rest Conduction: Heat loss due to contact with another surface Convection: Form of conductive heat loss

16 Heat Loss Evaporation  Heat transferred via water (sweat) on skin surface Evaporation rate depends on  Temperature and relative humidity  Amount of skin surface exposed 25% heat loss at rest Most important means of cooling off during exercise

17 Correction of overcooling 1. Detected by thermoreceptors in the hypothalamus. 2. Causes vasoconstriction. 3. Decreased sweating 4. Shivering

18 Keeping warm When it's cold, the muscle contracts pulls the hair up. A layer of warm air accumulates around the hair and insulates the organism. Heat retained

19 Shivering How does it work?

20 Voluntary responses In humans the cerebrum “makes” people feel cold or hot. They can then e.g. put on more clothes, eat a hot meal, exercise etc as appropriate.

21 Summary Describe the specific pathway that is used to keep us warm. Start with the temperature receptors in the skin. Describe the specific pathway that is used to cool us off. Start with the temperature receptors in the skin.


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