1. Controlling the Internal Environment I - Regulation of Body Temperature

2. Keywords (reading p. 865-873) Temperature effects
On reactions
On lipid bilayer
Endotherm
Ectotherm
Homeostasis
Thermoregulation
Behavioral thermoregulation
Physiological thermoregulation
Countercurrent heat exchange
Shivering
Effect of large size
insulation

3. Temperature
Affects the rates of reactions and the characteristics of macromolecules
Since organisms are machines made of macromolecules in which chemical reactions occur, temperature is an very important environmental feature

4. Temperature affects the rates of reactions, e. g
Temperature affects the rates of reactions, e.g. enzyme catalyzed reaction

5. Illustrated by gas molecules in a balloon slowing down if they are cooled

6. What is the magnitude of temperature effects for physiological processes or biochemical reactions?
Increase by 2-3 fold for a 10°C increase in temperature.
Q10 value = 2 to 3

8. Q10 values differ for different physiological processes or biochemical reactions
Some will speed up more, some less
This can ruin coordination of enzymes and reactions in metabolism, e.g., mitochondria

10. Temperature affects characteristics of macromolecules
Example: lipid bilayer

11. Lipid bilayer

12. Structure of an unsaturated phospholipid

13. Bilayer with unsaturated phospholipid stays fluid at lower temperatures

14. Since temperature has such a fundamental influence on biochemistry and physiology, animals:
A. regulate their body temperatures so they aren’t affected by temperature or can live under a wide range of conditions
B. Don’t regulate their temperature and accept metabolic consequences or live under small range of conditions

15. Endotherms vs. Ectotherms
Ectotherms have a body temperature the same as their environment
Endotherms use heat from metabolism
When endotherms are able to regulate their temperature they are called homeotherms

16. Example of endotherm and ectotherm

17. Homeostasis The steady-state physiological condition of the body
Internal fluctuations are small

18. Thermoregulation Regulation of body temperature
Can be behavioral or physiological

19. Behavioral thermoregulation

20. Example of physiological: countercurrent heat exchange

21. Arteries and veins in appendages are closely associated
Hot arterial blood passes heat to returning venous blood.
No heat is lost

22. Blood vessels in a bird leg

23. Similar mechanism in flippers of marine mammals

24. Blood flow can be controlled so that heat is lost
Blood flow can be controlled so that heat is lost. Blood goes to alternate veins close to the surface.

25. Countercurrent exchange is a trick used by many animals

26. Tuna heat exchanger

27. Great white shark

28. Body surface 7 12 17 22 27 5 10 15 20 25
Body core

29. Other tricks: shivering
Non-shivering thermogenesis: brown fat
Using ATP to contract muscles releasing heat instead of movement

30. Brown fat

31. Short-circuiting the mitochondria

32. Insect preflight warmup

34. Another trick: reduce heat loss
Large size - reduced surface area relative to volume prevents heat from escaping
Insulation - e.g., fur, feathers
Big problem for marine mammals since they have high body temp. and water conducts heat faster than air

35. Insulating fat (blubber)