Regulating the Internal Environment

1. Regulating the InternalEnvironment

2. Homeostasis • All organisms either: • regulate their internal environment • maintain relatively constant internal conditions • conform to the external environment • allow internal conditions to fluctuate along with external changes reptiles fluctuate with external conditions mammals internally regulate

3. Homeostasis Keeping the balance animal body needs to coordinate many systems all at once • temperature • blood sugar levels • energy production • water balance & waste disposal • nutrients • ion balance • cell growth • maintaining a “steady state” condition

4. Examples of Homeostasis • Osmoregulation • solute balance & gain or loss of water • Excretion • elimination of nitrogenous wastes • Thermoregulation • maintain temperature within tolerable range

5. Regulating the InternalEnvironment Focus: Water Balance

7. Unicellular  Multi-cellular • All cells in direct contact with environment • Direct exchange of nutrients & waste with environment • Internal cells no longer in direct contact with environment • Must solve exchange problem • Have to maintain the “internal ocean” Warm, dilute ocean waters Warm, dilute ocean waters

8. Diffusion is not adequate for moving material across more than 1 cell barrier What are the issues? Warm, dilute ocean waters Warm, dilute ocean waters O2 O2 aa aa CO2 CO2 NH3 CH CH2O CH2O CO2 CO2 CH NH3 O2 NH3 CO2 aa O2 CH NH3 CO2 CO2 CO2 NH3 CO2 CH CH2O O2 O2 NH3 CO2 NH3 CH2O NH3 aa O2 CH2O CH CH2O CO2 aa

9. Warm, dilute ocean waters Solving exchange problem • Had to evolve exchange systems for: • distributing nutrients • circulatory system • removing wastes • excretory system overcoming the limitations of diffusion

10. Ex. Osmoregulation • Water balance • freshwater = hypotonic • manage water moving into cells • salt loss • saltwater = hypertonic • manage water loss from cells • salt accumulation • land • manage water loss • need to conserve water Why do all land animals have to conserve water? • always need water for life • always lose water (breathing & waste) • may lose life while searching for water

11. H N H Animals can’t store proteins Various types of Waste disposal • What are waste products? How do we get rid of waste? • carbohydrates = CHOCO2 +H2O • lipids = CHOCO2 +H2O • proteins = CHON CO2+H2O+ N • nucleic acids = CHOPN  CO2+H2O+ P + N • relatively small amount in cell H OH | | | CO2 + H2O –C– C–OH | NH2= ammonia R

12. Nitrogenous waste disposal • Ammonia (NH3) • very toxic • carcinogenic • very soluble • Therefore easily crosses membranes • must dilute it & get rid of it… fast! • How you get rid of N-wastes depends on • who you are (evolutionary relationship) • where you live (habitat)

13. N waste • Ammonia • most toxic • freshwater organisms • Urea • less toxic • terrestrial • Uric acid • least toxic • egg layers • most water conservative

14. Freshwater animals • Nitrogen waste disposal in water • if you have a lot of water you can dilute ammonia then excrete • Ex. freshwater fish pass ammonia continuously through gills • need to excrete a lot of water anyway so excrete very dilute urine • Ex. freshwater invertebrates pass ammonia through their whole body surface

15. Land animals- the answer!! • Nitrogen waste disposal on land • evolved less toxic waste product • need to conserve water • urea = less soluble = less toxic • kidney • filter wastes out of blood • reabsorb H2O • excrete waste • urine = urea, salts, excess sugar & H2O • urine is very concentrated • concentrated NH3 would be too toxic

16. C O H H N N H H What is Urea? • 2NH2 + CO2= urea • combined in liver • Requires energy to produce • worth the investment of energy • Carried to kidneys by circulatory system

17. If you an Egg-laying land animal… • Nitrogen waste disposal occurs in egg • no place to get rid of waste in egg • need even less soluble molecule • uric acid = less soluble = less toxic • birds, reptiles, insects

18. What is Uric acid? Polymerized urea (What is a polymer?) • large molecule • precipitates out of solution • doesn’t harm embryo in egg • white dust in egg • adults excrete white paste • no liquid waste • white bird poop!

19. Human kidney Urinary system filters blood & helps maintain water balance (osmoregulation) Location of kidneys: rear of abdominal cavity Shape: They are a Pair bean-shaped organs Supply: supplied with blood • renal artery • renal vein

20. The Human Urinary System Includes: • Two kidneys • Two ureters • A urinary bladder • A urethra Overview of functions: • Kidneys filter blood and form urine • Other organs in system: collect, store and channel it out of the body

21. Outer layer is renal capsule (‘renal’ means relating to the kidneys’) Inside the renal capsule are two zones: Outer renal cortex Inner renal medulla renal arteries carry blood: to kidneys Renal veins carry blood: back to the lungs Zones of kidney

22. Once Urine is formed (we will get to that next) how does it exit the body? • Collects in renal pelvis (central cavity inside each kidney) • Tube-like ureter conveys fluid to urinary bladder • Bladder stores until sphincter at lower end opens and urine flows into the urethra where it is expelled outside of the body.

23. Kidney have over 1 million nephrons • Each begins in renal cortex • (outer layer) • The walls balloon outward and fold creating the cup-shaped Bowman’s capsule. • Past the capsule, the nephron twists and results in the proximal tubule – extends down into the loop of Henle and then back up into distal tubule • Distal tubule drains into collecting duct (where does it go from there? Ureter/bladder/out! Nephron: Basic Functional unit (parts of)

24. Another view: Note where the parts of the nephron are located in terms of the overall parts of the kidney – you should fill this in on your paper now! Descendinglimb Ascendinglimb To renal pelvis

26. Essentially…TWO systems within nephron… Interaction of circulatory & excretory systems (mammals) • Circulatory system • Includes: glomerulus = ball of capillaries • Excretory system Includes: • nephron • Bowman’s capsule • loop of Henle • descending limb • ascending limb • collecting duct

27. Additional System not discussed : endocrine (hormones) • antidiuretic hormone • Aldosterone • parathyroid hormone

28. To remove toxins from blood/filtrate • How? • liquid of blood (plasma) filtered into nephron • selective recovery of valuable solutes • (note the continuous nature of the capillary network and oxygen levels indicted by color) Nephron: Basic Functions

29. Specific functions (not in your PPT) • eliminates wastes from the body • regulates blood volume • regulates blood pressure • controls levels felectrolytes and metabolites • regulates blood pH. 

30. Specific roles of nephron… • Key functions • filtration • body fluids (blood) collected • water & soluble material removed • reabsorption • reabsorb needed substances back to blood • secretion • pump out unwanted substances to urine (K+ and H+) • excretion • remove excess substances & toxins from body

31. Nephron: Filtration (Khan, 7:17) • The renal artery branches into many arterioles (small arteries). • Each arteriole branches into a glomerulus (capillary bed inside the Bowman’s capsule) • This is a blood filtering unit!

32. Blood flow and the nephron • Blood travels through afferent arteriole and into glomerulus; a portion of fluid is filtered INTO Bowman’s capsule • The rest of the blood enters the efferent arteriole , which branches into peritubular capillaries that thread around nephron • Blood continues out to venules, leading to veins out of kidney

33. 47.5 gallons fluid is filtered daily What’s filtered? Filtered out (into Bowman’s capsule) H2O glucose salts / ions urea Not filtered out (stays in blood) cells Proteins

34. glomerulus inside Bowman’s capsule outer wall of Bowman’s capsule efferent arteriole (to peritubular capillaries) filtrate (to proximal tubule) afferent arteriole (from renal artery) p. 728a

35. Descendinglimb Ascendinglimb Restated… • Blood pressure drives water and small solutes from the blood into the nephron from glomerulus to Bowman’s capsule. • Later, variations in permeability along nephrons tubes determine what leaves (in urine) and what stays (in blood)

36. Following filtration…

37. Descendinglimb Ascendinglimb Re-absorption • Proximal tubule • reabsorbed back into blood • NaCl • active transport of Na+ • Cl– follows by diffusion • H2O • glucose • HCO3- • bicarbonate • buffer for blood pH

38. Descendinglimb Ascendinglimb • Loop of Henle • descending limb • high permeability to H2O (water leaves) • many aquaporins in cell membranes • low permeability to salt • few Na+ or Cl– channels • Reabsorbed (back into bloodstream) • H2O Re-absorption structure fitsfunction!

39. Descendinglimb Ascendinglimb • Loop of Henle • ascending limb • low permeability to H2O (water cannot leave) • Cl- pump • Na+ follows by diffusion • different membrane proteins • Reabsorbed (into blood) • Salts : maintains osmotic gradient Re-absorption

40. Na+ Cl– H2O renal medulla saltiest near turn Why? Not many Na or Cl channels in mb p. 729

41. Re-absorption (to blood) • Distal tubule • reabsorbed • Salts (Na, Cl) • H2O • HCO3- • bicarbonate

42. Secretion What?: Urea and excess ions (K+, H+) From?: peritubular capillaries to interstitial fluid – goes from interstitial fluid to filtrate in tubule How(do these compounds cross)? • transport proteins in wall of capillaries actively transport out

43. Secretion costs energy • Secretion costs the cell energy, therefore most of the processes are passive • Ion distribution with water allows for most passive processes!

44. Final stages of : Reabsorption & Excretion Descendinglimb Ascendinglimb • Collecting duct • reabsorbed • H2O • excretion • concentrated urine passed to bladder • impermeable lining

45. Osmotic control in nephron • How is all this re-absorption achieved? • tight osmotic control to reduce the energy costof excretion • use diffusioninstead of active transportwherever possible

46. Summary • Not filtered out • cells u proteins • remain in blood (too big) • Reabsorbed: active transport • Na+u amino acids • Cl–u glucose • Reabsorbed: diffusion • Na+u Cl– • H2O • Excreted • urea • excess H2O u excess solutes (glucose, salts) • toxins, drugs, “unknowns”

47. Any Questions?