1. Regulating the Internal Environment
Chapter 44
Regulating the Internal Environment

2. Homeostasis
Thermoregulation
Osmoregulation
Excretion

3. Homeostasis
All organisms must maintain a constant internal environment to function properly
Temperature pH
ion levels
hormones

4. Negative Feedback
Body Temperature Regulation

5. Coping with Environmental Fluctuations
Regulating:
Endotherms are thermoregulators
Fundulus-osmoregulator
Conforming:
Ectotherms
Many inverts- nonregulator
                                                                                                                                                         

6. Regulators & Conformers
Spider crab Libinia

7. Anadromous Salmon

8. Four physical processes account for heat gain or loss
Heat exchange by:
Conduction- transfer of heat between objects in direct contact with each other
Convection- heat is conducted away from an object of high temp to low temp
- Rate varies with different materials
Radiation- transfers heat between objects not in direct contact
- sun energy
Evaporation- change of liquid to vapor
- cooling

9. Heat exchange between an organism and its environment

10. Ectotherm vs Endotherm

11. Advantages of Endothermy :
Maintains stable body temp
Cooling & heating the body
cooling and heating the body
high levels of aerobic metabolism
sustains vigorous activity for much longer than ectotherms
Long distance running
Flight

12. Disadvantages of Endothermy :
Greater food consumption to meet metabolic needs
Human metabolic mate at 200C & at rest
1,300 to 1,800 kcal per day.
American alligator metabolic rate at 200C & at rest
60 kcal per day at 200C.

13. Mechanisms for thermoregulation
Insulation
Fur
Hair
Feathers
Fat
Blubber
Evaporative cooling
sweating, panting, bathing
Shivering
Nonshivering thermogenesis & brown fat
Circulation adaptations
Countercurrent exchange
Vasodilatation (cooling)
Vasoconstriction (heat conservation)
Behavioral responses

14. Countercurrent heat exchangers
Goose leg
Dolphin flipper

16. Evaporative Cooling
Hippos bathing

19. Brown Fat & Non-shivering Thermogenesis
Brown fat- generates heat
important in neonates, small mammals in cold environments, and animals that hibernate
Located in neck and in inner scapula area
Non-shivering Thermogenesis
Larges amts of heat produced by oxidizing fatty acids in the mitochondria

20. Regulating Body Temp in Humans

21. Acclimatization to New Env. Temps.
Endotherms (birds and mammals): grow a thicker fur coat in the winter and shedding it in the summer - and sometimes by varying the capacity for metabolic heat production seasonally.
Ectotherms compensate for changes in body temperature through adjustments in physiology and temperature tolerance.
For example, winter-acclimated catfish can only survive temperatures at high as 28oC, but summer-acclimated fish can survive temperatures to 36oC.

22. Some ectotherms that experience subzero body temperatures protect themselves by producing “antifreeze” compounds (cryoprotectants) that prevent ice formation in the cells.
In cold climates, cryoprotectants in the body fluids let overwintering ectotherms, such as some frogs and many arthropods and their eggs, withstand body temperatures considerably below zero.
Cyroprotectants are also found in some Arctic and Antarctic fishes, where temperatures can drop below the freezing point of unprotected body fluids (about -0.7oC).

23. Cells can often make rapid adjustments to temperature changes.
For example, marked increases in temperature or other sources of stress induce cells grown in culture to produce stress-induced proteins, including heat-shock proteins, within minutes.
These molecules help maintain the integrity of other proteins that would be denatured by severe heat.
These proteins are also produced in bacteria, yeast, and plants cells, as well as other animals.
These help prevent cell death when an organism is challenged by severe changes in the cellular environment.

24. Torpor in Ground Squirrels
Hibernation: long-term torpor as an adaptation to long-term winter cold and food shortage
Torpor in Ground Squirrels
Body temperature: 37oC
Metabolic rate: 85 kcal per day.
During the eight months the squirrel is in hibernation, its body temperature is only a few degrees above burrow temperature and its metabolic rate is very low.

25. Body Temperature and metabolism during hibernation of Belding’s ground squirrel

26. Osmoregulation
Osmoregulation- the control of the concentration of body fluids.
Diffusion- movement of substance from an area of greater concentration to an area of lower concentration
Osmosis- diffusion of water through a semipermeable membrane

27. Adaptation to Marine Environment
Reducing salt
Seabird and marine iguana- nasal salt secreting gland
Sea snake- sublingual gland
Crocodile- lacrimal gland
Fish gills- chloride cells
Shark- rectal gland

28. Salt Excretion in Birds

29. Nitrogenous Waste Excretion
Ammonia- toxic
Excrete directly into water- jellies
Detoxifyurea
Urea- need lots of water to get rid of
Uric Acid- birds & reptiles
more costly to produce than urea, but needs less water to be removed

30. Strategies to remove Nitrogenous Waste

31. Balancing NaCl in Blood
Osmoconformer: isoosmotic
Osmoregulator: hyper-, hypo-, ureoosmotic
Euryhaline: wide tolerance range
Stenohaline: narrow tolerance range
Osmols- total solute concentration in moles of solute/liter of solution

32. Less salt than external environment
Marine Fish: hypoosmotic
Less salt than external environment
H2O continually leaves body
continually drinks seawater
excretes salt through gills
produces small amts of dilute urine

33. More salt than external environment
Freshwater Fish: hyperosmotic
H2O continually enters body
does not drinks water
More salt than external environment
produces large amts of dilute urine

34. Shark and Coelacanth: ureoosmotic
Maintains high levels of urea and TMAO in blood
excretes salt through rectal gland
coelacanth
Rana cancrivora

35. Hagfish: ionosmotic nonregulator
Seawater concentration = internal concentration

36. Osmolarity in Freshwater and Saltwater
Osmolarity- measure of total solutes(dissolved particles)
Ions FW m osmol/l SW m osmol/l Na Cl
Ca variable 10
Total

37. Concentration of Ions Habitat Na+ Cl- Urea seawater sw 478 558
Habitat
Na+
Cl-
Urea
seawater sw
478
558
hagfish (Myxine)
537
542
lamprey fw
120 96
Goldfish (Carassius)
115
107
Toadfish (Opsanus)
160
Crab-eating frog (Rana)
252
227
350
Dogfish
287
240
354
freshwater ray
150
149
<1
coelacanth
197
199

38. Adaptations to Dry Environment
Many desert animals don’t drink water
Kangaroo rats lose so little water that they can recover 90% of the loss from metabolic water and gain the remaining 10% in their diet of seeds.
Also have long loop of Henle

40. Most excretory systems produce a filtrate by pressure-filtering body fluids into tubules.

41. Diverse excretory systems are variations on a tubular theme
Flatworms have an excretory system called protonephridia, consisting of a branching network of dead-end tubules.
The flame bulb draws water and solutes from the interstitial fluid, through the flame bulb, and into the tubule system.

42. Metanephridia consist of internal openings that collect body fluids from the coelom through a ciliated funnel, the nephrostome, and release the fluid through the nephridiopore.
Found in most annelids, each segment of a worm has a pair of metanephridia.

43. Insects and other terrestrial arthropods have organs called Malpighian tubules that remove nitrogenous wastes and also function in osmoregulation.
These open into the digestive system and dead-end at tips that are immersed in the hemolymph.

45. Nephron

47. Hormonal Control via Negative Feedback

48. Hormonal Control