Regulating the Internal Environment

1. Regulating the InternalEnvironment Water Balance & Nitrogenous Waste Removal

2. HOMEOSTASIS…Again! • Animal bodies must maintain balance between • Water uptake and water loss • Metabolic toxin build up / disposal • Both of these require movement of solutes into and out of the body in order for homeostasis to be maintained. • Usually discussed together in terms of a urinary or excretory system

3. Conformers vs. Regulators • Two evolutionary paths for organisms • regulate internal environment • maintain relatively constant internal conditions regardless of external conditions • conform to external environment • allow internal conditions to fluctuate along with external conditions osmoregulation thermoregulation endotherm ectotherm regulator regulator conformer conformer

4. What is Osmoregulation? • The regulation of water balance (water homeostasis) in an animal • ALL animals need to maintain homeostasis with regard to water in their cells • However, depending on where an animal lives, etc., what it must do to achieve homeostasis may be DIFFERENT • Fresh water vs. salt water vs. land

5. Osmoregulation in FRESH Water • Fresh water is Hypotonicto cells • water flows into cells • Follows concentration gradient from HI to LO • Could result in lysis • Also, salt concentrations decrease in cells as water increases (imbalance) • To combat both these outcomes, freshwater animals generally excrete large amounts of very dilute (mostly water) urine. • Indeed, freshwater fish kidney is more for maintenance of water balance than for removal of waste. hypotonic

6. Osmoregulation in SALT water • Salt water is hypertonic to cells • Water flows out of cells • Follows concentration gradient from HI to LO • Can result in cell death due to dehydration • Also, salt concentrations rise as water is lost AND due to continued ingestion of salt water • To combat water loss and salt imbalance. salt water animals… • Excrete excess salt through special glands and gills • Excrete urine that has VERY LOW water content hypertonic

7. Osmoregulation on LAND • dry environment (land) • Water loss a BIG issue; need to conserve water • Water loss due to breathing • Water lost in waste • Water may not be easy to find • may also need to conserve salt

8. 2nd Issue – Beyond Water Regulation: Homestasis and Metabolic Waste • As much as animals must regulate water loss, they must also control the toxic waste materials that accumulate among their cells as a byproduct of normal cellular processes. • Water balance and toxin disposal are closely related… • So..What exactly is the toxic waste animals make? • NITROGENOUS WASTE

9. Ok…So What is Nitrogenous Waste? • The short answer is that Nitrogenous Waste is AMMONIA • Ammonia is EXTREMELY TOXIC • VERY DANGEROUS • EVEN CARCINOGENIC

10. H O H | | | –C– C–OH N | H R Animalspoison themselves from the inside by digestingproteins! Why is Ammonia Made? • When food is digested, useful stuff is obtained (energy) and wastes are created… • carbohydrates = CHO • lipids = CHO • proteins = CHON • nucleic acids = CHOPN CO2 +H2O + Energy lots! CO2 +H2O + Energy verylittle  CO2 +H2O + N + Energy  CO2 +H2O + P + N + En Ammonia is made because it is a byproduct of metabolizing proteins to to get energy. cellular digestion…cellular waste What is this molecule? CO2+H2O + Energy NH2= ammonia AMINO ACID

11. So how do cells deal with this toxic ammonia? • Ammonia (NH3) • very toxic • very soluble • easily crosses membranes • The Answer(s): • MUST DILUTE AMMONIA & GET RID OF IT… FAST! • OR CHANGE AMMONIA into something LESS TOXIC • Which option you use depends on… • who you are (your evolutionary lineage – who you came from) • where you live (habitat) aquatic terrestrial terrestrial egg layer

12. Nitrogen Waste Disposal – FRESHWATER animals • Can afford to lose water • Deal directly with highly toxic ammonia by DILUTING it QUICKLY with LOTS of WATER • Nearly constant release of VERY dilute urine • Also diffuse ammonia across gill surface

13. Freshwater animals • Water removal & nitrogen waste disposal • remove surplus water • use surplus water to dilute ammonia & excrete it • need to excrete a lot of water so dilute ammonia & excrete it as very dilute urine • also diffuse ammonia continuously through gills or through any moist membrane • overcome loss of salts • reabsorb in kidneys or active transport across gills

14. Nitrogen Waste Disposal – Land Animals and Salt Water Fish • Cannot afford to lose water • Must CONVERT highly toxic ammonia to a LESS TOXIC form • Then it can be allowed to accumulate in the body to a degree • This reduces the needfor constant urination and water loss • Allows water to be CONSERVED • Ammonia is converted to less toxic UREA • This occurs in the liver

15. H H H H N N C O Nitrogen waste disposal on Land • Why is urea less toxic • larger molecule = less soluble = less toxic • 2NH2 + CO2 = urea • produced in liver • Also, kidney is well developed in land animals • filter solutes out of blood • reabsorb H2O (+ any useful solutes) • excrete waste • urine = urea, salts, excess sugar & H2O • urine is very concentrated • concentrated NH3 would be too toxic Urea costs energyto synthesize,but it’s worth it! mammals

16. Egg-laying land animals • Nitrogen waste disposal in egg • no place to get rid of waste in egg • need an even less soluble molecule • uric acid = BIGGER = less soluble = less toxic • birds, reptiles, insects itty bittyliving space! Don’t want to poison baby inside his own little house!

17. O O O N N N N H H H H Uric acid is the answer! (in eggs) • Is really polymerized urea • large molecule • precipitates out of solution • doesn’t harm embryo in egg • white dust in egg • adults still excrete N waste as uric acid • white paste • no liquid waste • uric acid = white bird “poop”!

18. Summary • Osmoregulation in fresh water • ALL about getting rid of excess water while maintaining salt concentrations • Osmoregulation on land • All about retaining water and maintaining salt concentrations

19. Adaptations to Life on LAND • Threat of dessication is perhaps the most important problem facing terrestrial life. • Only two animal groups (arthropods and vertebrates) have colonized land with great success. • Adaptations made: • Body coverings to prevent water loss • Waxy exoskeletons of insects • Shells of land snails • Multiple layers of dead keratinized cells in terrestrial vertebrates • Nocturnal activity • Water supply replenished by drinking, but some are so well adapted that they can survive in deserts without drinking at all • Kangaroo rat – recovers 90% of water lost by using metabolic water

20. Excretory Systems • Central to homeostasis • Dispose of metabolic wastes • Respond to imbalances in body fluids • Excrete more or less of some particular ion • Common theme to all solutions for water balance problem is… • Regulation of solute movement • if you regulate solute movement, you regulate water movement. • THE WATER WILL FOLLOW THE SOLUTES…

21. Excretory System Diversity Among Animals • Phylum Platyhelminthes • Excretory Organ: Protonephridium • Tubular excretory system • Branch throughout body • Capped by “flame bulb” – a structure with beating cilia • Beating of cilia draws water and solutes from body fluid through flame bulb and into tubule system • Urine from tubes empties into environment through pores. • Excreted fluid is very dilute in freshwater flatworms • Functions mainly in osmoregulation • Nitrogenous Wastes mostly diffuse through body surface

22. Excretory System Diversity Among Animals • Phylum Annelida • Metanephridia • Tubular excretory system • Internal ciliated openings collect fluids • nephrostome • Each segment of worm has a pair • Tubules immersed in coelomic fluid • Wrapped in capillaries • Both excretory and osmoregulatory functions

23. Excretory System Diversity Among Animals • Insects • Malpighian tubules • Attached to digestive tract • Remove nitrogenous wastes and function in osmoregulation • Excreted along with solid waste

24. Mammalian Excretory System • Central to homeostasis • Water Balance • Nitrogenous waste disposal • REMEMBER: Common theme to all solutions for water balance problem • Regulate the solutes and the water will follow • if you regulate solute movement, you regulate water movement.

25. 4 Main processes used in Mammalian Excretory Systems: blood filtrate • Filtration • Unwanted stuff is filtered out of the blood • Reabsorption • Good stuff that might have been filtered out with the bad is reclaimed • Secretion • PUMP any additional unwanted solutes OUT of the body and add to the filtrate • Excretion • Concentrated urine is expelled from the body concentratedurine

26. Mammalian Kidney inferiorvena cava aorta adrenal gland kidney nephron ureter renal vein& artery Epithelial cells line the nephron bladder urethra Kidney cross section

27. Nephron • Functional units of kidney • 1 million nephronsper kidney • How it Works • Blood plasma is filteredinto nephron • high pressure of blood pushes water and solutes out of capillaries and into nephron • Nephron selectively reabsorbsvaluable solutes & H2O back into the bloodstream “counter current exchange system”

28. How candifferent sectionsallow the diffusionof different molecules? Parts of Nephron • Bowman’s capsule • proximal tubule • loop of Henle • descending limb • ascending limb • distal tubule • collecting duct Bowman’s capsule Mg++ Ca++ Proximal tubule Distal tubule Amino acids Glomerulus Glucose H2O H2O Na+ Cl- H2O H2O H2O Na+ Cl- H2O H2O H2O H2O Collecting duct Loop of Henle

29. Nephron: Filtration • Intersects with circulatory system • Glomerulus • Ball of capillaries • Blood pressure pushes solutes and water out of glomerulus • Bowman’s Capsule • Funnel shaped beginning of nephron • Glomerulus fits inside of Bowman’s capsule • Catches filtrate pushed out of capillaries and passes it to the rest of the nephron • filtered out of blood • H2O • glucose • salts / ions • urea • not filtered out • cells • proteins high blood pressure in kidneysforce (filter) H2O & solutes out of blood vessel BIG problems when you start out with high blood pressure in systemhypertension = kidney damage

30. Nephron: Re-absorption • Proximal tubule • Reclaims for the body: • NaCl • active transport • H2O • Passive transport • Glucose • HCO3- • bicarbonate • buffer for blood pH

31. structure fitsfunction! Nephron: Re-absorption • Loop of Henle-descending limb • high permeability to H2O • many aquaporins in cell membranes • low permeability to salt • few Na+ or Cl– channels • Water flows OUT of the descending limb from HI to LO concentration gradient • As water flows out of the descending limb, the concentration of solution left inside gets increasingly salty. • This will set up for events in next part of nephron • Bottom line: reabsorbed • H2O

32. HI H2O IN TUBE Water out of nephron due to diffusion LO H2O outside of Tube Hi SOLUTE conc. outside of tube due to reabsorption of solutes into Kidney tissue at Proximal Tubule Descending Limb

33. structure fitsfunction! Nephron: Re-absorption • Loop of Henle - ascending limb • Concentration of salt has become high at bottom of loop of Henle due to water reabsorption • Salt now diffuses out of the ascending limb • It can flow with its concentration gradient because it has gotten so concentrated within the nephron • Higher in the ascending loop, NaCl must be PUMPED out b/c the salt concentration will have lessened on its journey up. • Also, low permeability in ascending limb to H2O; it can’t get out well. • Few aquaporins… • Bottom Line: reabsorbed • salts • maintains osmotic gradient in kidney tissue Hi conc. Salt in tube

34. Nephron: Re-absorption • Distal tubule • reabsorbed • salts • H2O • HCO3- • bicarbonate

35. Nephron: Reabsorption & Excretion • Collecting duct • reabsorbed • H2O • Also… • Salt • Urea?? • Helps maintain concentration gradient • excretion • concentrated urine passed to bladder • impermeable lining

36. 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

37. May I please have a pass? I’ve gotta go! Summary • Not filtered out • cells proteins • remain in blood (too big) • Reabsorbed: active transport • Na Cl u glucose • amino acids • Reabsorbed: diffusion • NaCl • H2O • Excreted • urea • excess H2O u excess solutes (glucose, salts) • toxins, drugs, “unknowns”

38. Any Questions?

39. Regulating the InternalEnvironment Maintaining Homeostasis

40. high low Negative Feedback Loop hormone or nerve signal lowersbody condition (return to set point) gland or nervous system sensor specific body condition sensor raisesbody condition(return to set point) gland or nervous system hormone or nerve signal

41. high low Nervous System Control Controlling Body Temperature nerve signals brain sweat dilates surfaceblood vessels body temperature brain constricts surfaceblood vessels shiver nerve signals

42. increasethirst pituitary nephron high low Endocrine System Control Blood Osmolarity ADH increasedwaterreabsorption blood osmolarity blood pressure ADH = AntiDiuretic Hormone

43. Maintaining Water Balance Get morewater intoblood fast • High blood osmolarity level • too many solutes in blood • dehydration, high salt diet • stimulates thirst = drink more • release ADH from pituitary gland • antidiuretic hormone • increases permeability of collecting duct & reabsorption of water in kidneys • increase water absorption back into blood • decrease urination H2O H2O Alcohol suppresses ADH… makes youurinate a lot! H2O

44. high low JGA adrenalgland nephron Endocrine System Control Blood Osmolarity Oooooh,zymogen! JGA = JuxtaGlomerular Apparatus blood osmolarity blood pressure increasedwater & saltreabsorption in kidney renin aldosterone angiotensinogen angiotensin

45. adrenalgland Maintaining Water Balance Get morewater & salt intoblood fast! • Low blood osmolarity level or low blood pressure • JGA releases renin in kidney • renin converts angiotensinogen to angiotensin • angiotensin causes arterioles to constrict • increase blood pressure • angiotensin triggers release of aldosterone from adrenal gland • increases reabsorption of NaCl & H2O in kidneys • puts more water & salts back in blood Why such arapid responsesystem? Spring a leak?

46. increasethirst pituitary nephron high JuxtaGlomerularApparatus low adrenalgland nephron Endocrine System Control Blood Osmolarity ADH increasedwaterreabsorption blood osmolarity blood pressure increasedwater & saltreabsorption renin aldosterone angiotensinogen angiotensin

47. Don’t get batty… Ask Questions!!

48. Nitrogen waste • Aquatic organisms • can afford to lose water • ammonia • most toxic • Terrestrial • need to conserve water • urea • less toxic • Terrestrial egglayers • need to conserve water • need to protectembryo in egg • uric acid • least toxic