1. Temperature, Osmotic Regulation, and the Urinary System Homeostasis – the ability of living organisms to maintain internal conditions within an optimal range –a steady-state physiological condition, extremely important for the proper functioning of cells

2. Homeostasis Thermoregulation (temperature) Osmoregulation (solute and water balance) Excretion (rids system of nitrogen-containing metabolic byproducts)

3. Thermoregulation The rate of any chemical reaction is affected by temperature The rate of reaction increases with increasing temperature The rate of reaction decreases with decreasing temperature Q 10 is a quantitative examination of how reaction rates vary with temperature

4. Thermoregulation, Q 10 Q 10 – the ratio between the rates of a reaction at two temperatures that differ by 10°C Q 10 = R T+10 / R T For example, if Q 10 = 2, then for every 10°C increase in temperature, the rate of reaction doubles (increases by a factor of 2)

5. Thermoregulation, Q 10 For most enzymes, Q 10 = 2 Q 10 can also be applied to metabolism (the set of all chemical reactions that occur in living organisms in order to maintain life) In most organisms, the Q 10 of metabolism is 2-3 In some organisms, their Q 10 is close to 1 –Little to no change in metabolic rate with temperature

6. Thermoregulation The reactions in your body that make up your metabolism are constantly producing heat –Can be dissipated or used to raise internal body temperature –Metabolic rate and body temperature are inter-related Lower body temperatures do not permit high metabolic rates

7. Thermoregulation External temperatures affect metabolism as well As external temperatures decrease, tremendous heat loss can occur As body temperatures are reduced, it becomes more difficult to generate metabolic heat

8. Thermoregulation Internal body heat = heat produced + heat transferred or Body heat = heat produced + (heat gained – heat lost)

9. Thermoreguation Four mechanisms of heat transfer –Radiation: no direct contact; e.g., Sun –Conduction: direct transfer of heat from one object to another –Convection: involves movement of gas or liquid –Evaporation: energy loss, conversion of liquid  gas

10. Thermoregulation

11. Thermoregulation: Ectothermy vs. Endothermy

12. Endothermy vs. Ectothermy Ectothermy –Lower energy requirements (more efficient at converting energy into biomass) –Typically limited to diurnal environments, tropical and semi-tropical environments, short bursts of activity Endothermy –May be active at night; in tropics to the poles –Very high energy requirements

13. Thermoregulation Organisms have evolved adaptations to regulate their body temperature (and reduce heat loss to their environment) –Changes in surface area, temperature difference and heat conduction –In Ectotherms Presence of ’antifreeze’ (cold temps) Different enzyme systems (hot temps)

14. Thermoregulation –In Endotherms Increase muscular activity; shivering (cold temps) Adjusting blood flow through skin (cold or hot) Adjusting amount of heat loss through evaporation Adjusting amount of insulation Adjusting proportion of body parts in order to reduce or increase surface area

16. Thermoregulation www.flickr.com/photos/hearman/9884614/ http://dive.scubadiving.com/d2d_archive/read.php?f=1&t=920399&a=2& www.flickr.com/photos/80835774@N00/2096697676/

17. Thermoregulation Adaptations to regulating temperatures can be both physiological and behavioral Most invertebrates (ectodermic) use behavior to adjust their temperature –Orientation of body towards sun –Shivering www.flickr.com/photos/fxd/2760414614/

18. Countercurrent Heat Exchange Vertebrate ectoderms, as well as some endodermic birds and mammals regulate their internal body temperature by way of a counter-current heat exchange system –Warm blood pumped from within the body is used to warm the cooler blood returning from the extremities –Ingenious! Blood leaving the warm interior loses its heat to returning vessels just before they enter (cooler) extremities

19. Countercurrent Heat Exchange

20. Countercurrent Heat Exchange in Action!!!

21. Marine birds do this as well!

22. Countercurrent Heat Exchange

24. Common dolphin dorsal fin

26. artery vein

27. Thermoregulation In general, ectotherms have low metabolic rates, which has the advantage of correspondingly low intake of food Some endoderms can prevent overheating by perspiring (sweating) and panting Mud baths are particularly useful in preventing overheating

28. Adaptations to Temperature Extremes When temperatures fall below a critical threshold, the animal must resort to thermogenesis, the use of normal energy metabolism to produce heat –Shivering (muscular activity) –Nonshivering thermogenesis Occurs primarily in brown fat (hibernating animals, babies, arctic mammals)

29. Adaptations to Temperature Extremes In mammals, thermoregulation is controlled by the hypothalamus When the temperature of blood exceeds 98.6°F, neurons in the hypothalamus detect the temperature change, stimulates its heat-losing center –Causes dilation of peripheral blood vessels, bringing more blood to the surface to dissipate heat –Stimulates sweating; suppression of metabolism-stimulating hormones

30. Adaptations to Temperature Extremes When the temperature of blood falls below 98.6°F, the heat promoting center of the hypothalamus is stimulated –Causes constriction of blood vessels –Inhibit sweating –Epinephrine produced by adrenal medulla to stimulate metabolism

31. Adaptations to Temperature Extremes Torpor – decrease of metabolic rate over a relatively short period of time –Reduces the need for food intake by reducing metabolism –More common in smaller animals; larger animals have too much mass to effectively cool

32. Adaptations to Temperature Extremes Hibernation – drastic decrease in metabolic rate over a long period of time, in response to colder temperatures Effective only in midsize animals –Too big; costs more energy to increase temperature than what is saved over winter –Too small: can’t store enough energy –Estivation – large decrease in metabolic rate over a long period of time, in response to hotter temperatures (& food, water supplies)

33. Thermoregulation Fever – an increase in body temperature to levels above normal Considered to be one of the body’s (normal) immune mechanisms to inhibit the growth of bacteria or viruses Extremely high fevers, however, are detrimental and can result in seizures and hallucinations