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Lecture 24

Lecture 24. Biology 1108 Chapter 44: Control of the Internal Environment. Learning Objectives (1 of 3). Contrast Osmoregulation in salt water & fresh water fish Ectotherms and endotherms Define Homeostasis Discuss “Goose bumps”. Learning Objectives (2 of 3). Contrast:

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Lecture 24

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  1. Lecture 24 Biology 1108 Chapter 44: Control of the Internal Environment

  2. Learning Objectives (1 of 3) • Contrast • Osmoregulation in salt water & fresh water fish • Ectotherms and endotherms • Define • Homeostasis • Discuss • “Goose bumps”

  3. Learning Objectives (2 of 3) • Contrast: • Ammonia excretion in fish, birds, mammals • Recall: • Maximum amount of water lost to sweat • Functions of liver, kidneys • Function of each part of the excretory system • Discuss: • Seasonal dehydration • Water bear survival • Stone Mountain fairy shrimp

  4. Learning Objectives (3 of 3) • Some words to define: • Trehalose • Identify ALL urinary system parts

  5. Homeostasis • This chapter: “Control of the Internal Environment” • Homeostasis = maintenance of stability • For today, 2 types of internal control: • Temperature (thermoregulation) • Chemical (osmoregulation)

  6. Thermoregulation • Maintenance of a certain body temperature • Two basic types of animals • Endotherms vs. Ectotherms

  7. Ectotherms • Most of body heat comes from outside • Often must use behavior to regulate heat gain/loss • Reptiles bask in sun or on hot rock • Fish find water suitable for body temp • Trout prefer cold • Bass prefer somewhat warmer

  8. Endotherms • Most of heat comes from metabolism • Examples: • Birds • Mammals • Great white sharks

  9. Endotherms: Limiting Heat Loss • Most endotherms must limit heat loss • Thick body fat • Feathers in birds • Fur in mammals • Counter current exchange

  10. “Goose Bumps” • Each hair follicle has a tiny muscle • When cold, muscles raise hairs • Insulating air is trapped • Works better for furry mammals • We still have it as vestige of our evolutionary history • Birds have similar strategy

  11. Counter Current Heat Exchange • Limits heat loss through blood • Where is it found? • Great white shark • Penguin legs

  12. How it works: • Veins and arteries close together • Thermal energy flows from warmer to colder • Outgoing blood warms incoming blood • Heat stays towards body’s center

  13. How it Works

  14. Endotherms: Cooling • Sometimes cooling necessary • Increased blood flow to skin helps • Elephants dilate ear arteries & flap • Humans flush • Sweating causes evaporative cooling

  15. Osmoregulation • Control of internal chemical environment • Ex: Enzymes require certain pH & salinity to work properly • Saltwater & freshwater fish must have opposite strategies for osmoregulation!

  16. Hypotonic vs. Hypertonic • Just remember to ask, “How is the outside?” • If less concentrated, then environment is hypotonic (lower in salt) • If more concentrated, then environment is hypertonic (higher in salt)

  17. Freshwater Fish: Ion Balance • Constantly loses ions to hypotonic (lower salt) environment • Sodium Na+ • Calcium Ca+ • Chloride Cl- • To compensate: • Gills absorb ions from water • Digestive system absorbs ions from food

  18. Freshwater Fish: Water Balance • In danger of having too much water • These fish must avoid drinking • Kidneys produce copious, dilute urine

  19. Saltwater Fish: Ion Balance • Fish at risk of having too many ions • To compensate, gills constantly expel ions

  20. Saltwater Fish: Water Balance • Environment is hypertonic (salty) • Will rob fish of water • To compensate: • Saltwater fish drink lots! • Produce very little, but concentrated urine

  21. Question: • Let’s say you’re dehydrated • Which is absorbed by your body more quickly: • A sports drink? • Plain water?

  22. Dehydration from Sweating • Body sweats to cool skin • Up to 2 liters per hour during heavy exercise! • 2% loss affects performance • Excess loss reduces blood flow to skin, sweating stops • At 5%, heat stroke can occur

  23. Seasonal Dehydration • Problematic for aquatic or moisture-requiring organisms • Strategies • Lay desiccation-resistant eggs • Evolve to tolerate drought

  24. Stone Mountain Fairy Shrimp • Endangered species • Stone Mountain, GA is only home! • Live in ephemeral (temporary) pools • All adults die when pool dries up • Eggs resistant to dessication • Can survive for years

  25. Water Bears Survive Dehydration! • Can lose 95% of body moisture! • Homeostasis requirement relaxed • Remain inactive for decades • Rehydrate in minutes • Water bears = Phylum Tardigrada

  26. More Amazing Feats: • Temperature: -270°C to 150°C • Pressure: 6000atm = 10km under sea! • Pure alcohol! • Websites • Nature • Tardigrade Animations

  27. Dehydration in Nematodes • Some nematodes can survive dessication • Normally, cell membranes would collapse, proteins would break down • Nematodes have special sugar (trehalose) which prevents damage • Trehalose used to preserve some protein-based pharmaceuticals

  28. Homeostasis Stretch

  29. Nitrogenous Wastes • Proteins have many nitrogen-containing amino groups • In waste products, they become ammonia • Very toxic! • Body must eliminate ammonia!

  30. Eliminating Ammonia • Ammonia is chemically simple • Fish excrete ammonia directly through gills, directly to water • Terrestrial animals must convert ammonia to less toxic chemicals

  31. Terrestrial Animals: Urea • Mammals make urea • Water soluble (excreted in urine) • Disadvantage: energy cost (more complex)

  32. Terrestrial Animals: Uric Acid • Birds, reptiles make uric acid • Not water soluble (excreted as white paste) • Highest energy cost (most complex)

  33. Excretory System • We have 2 kidneys • Filters blood, producing urine • Each has 80 km of tubing! • Tubing has semipermeable membrane • Sorts waste molecules out of blood

  34. Overview of Excretory System • Contrast ureter vs. urethra • Ureter connects kidneys to bladder • Urethra (with an A) connects bladder to outside (think, AHHHH!)

  35. Anatomy of the Kidney • Contrast cortex (outer surface) vs. medulla (inner parts) • Note that renal pelvis collects urine

  36. Anatomy of the Nephron • Contrast filtrate vs. urine • Filtrate removed from blood by Bowman’s capsule • Has valuable solutes, glucose • Urine is filtrate after refining by the rest of the nephron • Returns solutes, glucose to blood stream

  37. Nephron Details • Filtrate goes from glomerulus, to proximal tuble, loop of Henle, distal tubule • Becomes more concentrated on journey

  38. Dialysis • If kidneys fail, patient must receive blood-cleansing treatment, or death will occur • Dialysis machine has pump, semi-permeable tubing, dialyzing solution • Treatments expensive • Three times a week, 4-6 hours each time

  39. Liver • Many homeostatic functions, including: • Changing ammonia into urea • Converting alcohol & drugs into inactive wastes • Regulation of blood glucose levels

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