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

2. 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

3. 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

4. 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.

5. 3 basic components of a feedback system
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

6. 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.

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

8. Maintenance of Body Temperature
SKIN

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

11. Vasoconstriction and Vasodilatation

12. Correction of overheating
Detected by thermoreceptors in the hypothalamus.
Causes vasodilation.
Sweating

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

14. 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

15. Heat Loss Evaporation Evaporation rate depends on
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

16. Correction of overcooling
Detected by thermoreceptors in the hypothalamus.
Causes vasoconstriction.
Decreased sweating
Shivering

17. 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

18. Shivering
How does it work?

19. 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.

20. 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.