Ch. 44: REGULATING THE INTERNAL ENVIRONMENT

1. Ch. 44: REGULATING THE INTERNAL ENVIRONMENT

2. Introduction • A.Homeostasis: • Thermoregulation = Regulation of Body • Temperature • Osmoregulation = Regulation of solute • and water balance • Excretion = Control of Nitrogen containing • waste • Regulators v. Conformers: • Regulators: Maintain constant internal • environment • Conformers: Allow for internal environment • to change over a range of external • conditions.

4. Thermoregulation: Regulation of Body Temp. • Q10 Effect: The rate at which an enzyme- • mediated chemical reactions increases for • every 10° C temperature increase. Ex. Rate of glycogen hydrolysis in a frog is 2.5 time greater at 30° C than 20° C. It’s Q10 for that reaction is 2.5. • Temperature has a great effect on an animal’s • ability to do work. • Four physical processes account for heat gain • or loss: • Conduction: direct transfer of thermal • motion (heat) between molecules of objects • in direct contact with each other, as when • an animal sits on a pool of cold water or on • a hot rock.

5. Convection: is the transfer of heat by the • movement of air or liquid past a surface. • Radiation: is the emission of electro- • magnetic waves by all objects warmer than • absolute zero, including an animal’s body, • the environment, and the sun. • Ex. Transfer of heat from animal’s body.

6. Evaporation: Loss of heat from liquid to • gas.

7. Sources of Body Heat: • 1.Ectotherms: determined by the • surrounding environment. • 2.Endotherms: determined by metabolic • rates.

8. Advantages of endothermy: • High level of cellular respiration; allows for • endotherms to perform vigorous activities • much longer than ectotherms. • Stable body temperature allows for an • endotherm to live in fluctuating temps, that • are characteristics of terrestrial landscape. • However, endothermy requires much more energy intake than ectothermy. Example: 20°C, a human at rest has a metabolic rate of 1,300 to 1,800 kcal/day and an American alligator, has a metabolic rate of only about 60 kcal per day at 20°C.

9. Thermoregulation involves physiological and • behavioral adjustments that balance heat gain • and loss. Four categories of adpations that help animals thermoregulate: • Adjusting the rate of heat exchange • between the animal and its surroundings: • Insulation (hair, fur, feathers, fat) • reduces the flow of heat between an • animal and its environment. • Adaptations of the circulatory system: • Vasodilation: an increase in the • diameter superficial blood vessels, • increasing the transfer of body heat to a • cool environment by radiation, conduction, • and convection.

11. Vasoconstriction: Reduces blood flow and heat transfer by decreasing the diameter of superficial vessels.

13. Countercurrent heat exchanger: special arrangement of blood vessels that help trap heat in the body core; helps reduce heat loss in many endotherms. Heat from the body core in the arteries are transferred to the veins.

14. Cooling by evaporative heat loss: • evaporation at skin and by breathing; as • water evaporates, it also removes the heat. • -Panting • -Sweating • -Bathing • Behavioral responses: Sun basking, lying • in shade, hibernation, and migration, etc. • Changing the rate of metabolic heat • production: greatly increase heat • production when exposed to cold (will be • discussed further in the next section) • -Applies only to endotherms

15. Endothermy: Mammals and Birds • Body temp range: mammals = 36-38° C • birds = 39-42° C • 2.Must counteract the constant heat loss to • the environment by: • a.High metabolic rate • b.Shivering to produce heat • c.Certain hormones can cause mitochondria • to increase their metabolic activity and • produce heat instead of ATP. This is • called NST (Nonshivering • Thermogenesis). It takes place • throughout the body, and also in a • specialized region called “brown fat.”

16. Insulation: Hair, feathers, fat • Vasodilation/Vasoconstriction • Panting • Sweating/Spreading saliva on body • surfaces • Ectothermy: Amphibians and Reptile • Body temp range: 7° to 25° C. • Behavioral adaptations: Moving to shade • or sunny spots. • Galapagos Island Iguana: vasoconstrict • their superficial blood vessels to conserve • body heat. • 4.Large Endothermic Reptiles: Female • pythons, incubating eggs, increase their • metabolic rates by shivering, generating • heat (Dinosaurs endothermic??).

17. Ectothermy: Fishes • Conformers: within 1-2° C of their • surroundings. • Specialized endothermic fishes: powerful • swimmers like bluefin tuna, swordfish, and • great white sharks, have circulatory • adaptations that retain metabolic heat in • the body.

18. -Endothermy in great white sharks: countercurrent heat exchanger in its swimming muscles.

19. Ectothermy: Invertebrates • Aquatic Invertebrates: conformers • Terrestrial Invertebrates are actually endo- • thermic as they can elevate body temp by • moving their powerful flight muscles. -Bees and moths (Ex. Hawk moth) -Countercurrent heat exchanger at the thorax -Honeybee social behavior: huddle and shiver together in cold weather

21. Feedback Mechanisms in Thermoregulation: • Nerve cells that regulate thermoregulation • is concentrated in the hypothalamus.

22. The hypothalamus is like a thermostat, • responding to changes in body temperature • above and below a set point by activating • mechanisms that promote heat loss or gain.

23. Adjusting to Changing Temperature: • Many animals adjust to a new range of • environmental temperatures over a period • of days or weeks. This is called • acclimatization. • Acclimatization in birds and mammals: • Adjust the amount of insulation (thicker • coat of fur in the winter, etc), adjust the • metabolic heat production. • Acclimatization in ectotherms: process of • compensating for changes in body • temperature through adjustments in • physiology and temperature tolerance. • Ex. Winter-acclimated catfish can only survive • temps as high as 28°C, but summer-acclimated • fish can survive temps to 36°C.

24. -Acclimation in ectotherms often include • adjustments at the cellular level: • Variant enzymes are produced that have the same function, but has a different optimal temperature. • Membranes can also change the proportions of saturated and unsat. lipids they contain, which helps keep membranes fluid at different temps. • Antifreeze chemical: prevents ice from forming in cells. Ex. Cryoprotectants • Stress-Induced proteins (i.e., heat- shock proteins): help maintain the integrity of other proteins that would otherwise be destroyed by heat.

25. Torpor conserves energy during • environmental extremes. • Torpor: a physiological state in which • activity is low and metabolism decreases. • Hibernation: long-term torpor • a.Body temp declines • b.Low metabolic rate •  Allows for survival on limited supplies of • energy • Belding squirrel: hibernates for 8 months; body temp during hibernation is near freezing; arouses for a few hours every week or two.

26. Body temp and metabolism during Hibernation of Belding’s ground squirrel:

27. Estivation: Summer torpor; slow • metabolism and inactivity during high • temps and when water is scarce. • Daily torpor: Small endotherms; occurs • at night or during the day (during hours • when they cannot feed).

28. Water Balance and Waste Disposal • Osmoregulation: management of water • content and solute composition. • Water balance and waste depends on • transport epithelia. • Transport epithelium: layers of epithelial • cells that move specific solutes in controlled • amounts in particular directions. • An animal’s nitrogenous wastes are • correlated with is phylogeny and habitat. • -Nitrogenous waste is produced when macro- • molecules are broken down for energy. • -Nitrogen is removed in the form of • ammonia.

30. Ammonia: small and very toxic molecule • created when macromolecules are broken • down. • Can only be tolerated at low • concentrations  requires access to lots • of water. • Ammonia release is common in aquatic • species. • Released easily by diffusion to the • surrounding water. -Marine invertebrates: Diffuses across the entire body surface. -Fish: lost as ammonium ions (NH4+) across the epithelium of gills, while the kidneys extract minor amounts of nitrogenous wastes.

31. Urea: Made in the liver by combining • ammonia with carbon dioxide and excreted • by the kidneys. • Low toxicity  allows for animals to • store and transport urea safetly at high • concentrations. • Disadvantage: Requires energy to • convert ammonia into urea. • Uric Acid: Land snails, insects, birds, and • reptiles excrete uric acid. • Insoluble in water and can be excreted • as a semisolid paste with very little water • loss (advantage). • Disadvantage: Requires a considerable • amount of ATP to synthesize it from • ammonia.

32. Osmoregulation: • Osmoconformers: internal osmolarity is • the same as that of its environment. • Osmoconformers often live in water that • has a very stable composition. • Osmoregulator: animals that must • control their internal osmolarity. • Most animals are stenohalines (animals • that cannot tolerate substantial changes in • external osmolarity. • Euryhalines are animals that can survive • large fluctuations of external osmolarity. • Example: Salmon migrate back and forth • between fresh and salt water.

33. Maintaining water balance in the sea: • Most marine invertebrates are osmo- • conformers. • Marine fishes (Class Osteichthyes) • constantly lose water through their skin • and gills. • -gain water through food, and drinking • large volumes of water (with salt disposed • by active transport out of the gills) • -very little urine is produced • Cartilagenous fish, like sharks (Class • Chondrichthyes) do not have large water • loss due to high concentrations of urea in • their body fluids, along with trimethylamine • oxide (TMAO), which protects proteins from • the urea; body is hyperosmotic to seawater.

34. Maintaining osmotic balance in freshwater: • Since freshwater fish are hypotonic to their • surroundings, they are constantly gaining • water by osmosis. • Freshwater fish excrete large amounts of • very dilute urine and regain lost salts in • food. • Paramecium have • a contractile • vacuole to • pump water out:

35. Salmon must adjust to different environ- • ments as they migrate from freshwater to • saltwater. • Ocean: Salmon drink seawater and excrete • salt from their gills. • Freshwater: Salmon cease drinking, begin • to produce lots of dilute urine and their • gills take in salt from water.

36. Freshwater fish are hypertonic to their environment. Saltwater fish are hypotonic to their environment.

37. Special Problems of Living in Temporary • Waters: Anhydrobiosis (“life without water”) • Example: Tardigrades, or water bears • -Tiny invertebrates • -Active, hydrated state (85%) • -Inactive, dehydrate state (2%); can • survive in this state for decades Active State Inactive State

38. Maintaining Water Balance On Land: • 1.Loss of water = Largest problem for • terrestrial organisms • Adaptations: • -Waxy cuticle • -Skin • -Drinking water and eating moist food

39. Excretory Systems A. An Overview: • Urine is produced in two steps: • a. Body fluid is collected – Filtration • b. Reabsorbtion • Filtrate: water and • small solutes, such • as salts, sugars, • amino acids, and • nitrogenous wastes • After filtration, the filtrate is modified in the excretory tubule as valuable substances from the filtrate are reabsorbed.

40. Diverse excretory systems: 1. Protonephridia: Flame-Bulb System • Network of dead-end tubules lacking • internal openings. • b.Tubes branch throughout body, capped by • a flame bulb. • Cilia draws water and solutes • into flame bulb. • Urine is moved • outwards through • the nephridiopores. • Urine = dilute • Most metabolic • waste diffuses out • across the body surface • or into body cavity and out through mouth

41. Metanephridia: tubular excretory system • -Internal openings that collect body fluid • -Ciliated funnel, the nephrostome, which • collects fluids from coelom • -Each body segment contains a pair of • metanephridia

42. Malpighian Tubules: In insects and • terrestrial arthropods • -Remove nitrogenous wastes and • osmoregulate • -Tubes open to digestive tract and the • tips are immersed in the hemolymph

43. -Epithelial lining the tubules secrete solutes and nitrogen wastes -Water follows the solutes into tubule -Most solutes are pumped back into the hemolymph -Water follows the solutes, and nitrogen waste (uric acid) is eliminated as dry matter (conserves water!)

44. Vertebrate Kidneys: • -Functions: osmoregulation and excretion • -Compact, hightly organized tubules • -Associated with capillaries and ducts • -Mammals have a pair of kidneys: • Bean shape • Supplied with blood by the renal artery and a renal vein • Urine exits each kidney through a duct called the ureter • Each ureter drains into the bladder • Urine is expelled through a tube called the urethra

45. Female and Male urinary tracts

46. C.Structure and Function of the Nephron and their Associated Structures: 1.Two distinct regions of the kidney: a. Renal Cortex b. Renal Medulla

47. 2.Nephron = the functional unit of the kidney 3.A nephron is a long tubule and a ball of capillaries called the glomerulus 4.Bowman’s capsule: the end of the tubule that surrounds the glomerulus. 5.Average human kidney has a million nephrons, with a total tubule length of 80 km.

49. Filtration of blood: • -Blood pressure forces fluid from blood in • the glomerulus into the lumen of • Bowman’s capsule • -Specialized cells called podocytes are • permeable to solutes and water • -Filtrate: salts, glucose, and vitamins; & • nitrogenous wastes • Pathway of the Filtrate - Passes through 3 • regions of the nephron: Proximal tubules  Loop of Henle  Distal Tube (empties into collecting duct)

50. 8.Two types of nephrons: -Cortical (reduced or no loop of henle) -Juxtamedullary well-developed loop of henle; goes into renal medulla)