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Example 3: Osmoregulation

Homeostatic Mechanisms 1 (function). Example 3: Osmoregulation. Big Questions:. How do the physiological systems of organisms help the organism maintain homeostasis? How have the physiological systems of organisms been adapted to the constraints of the environments that organisms live in?.

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Example 3: Osmoregulation

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  1. Homeostatic Mechanisms 1 (function) Example 3: Osmoregulation

  2. Big Questions: How do the physiological systems of organisms help the organism maintain homeostasis? How have the physiological systems of organisms been adapted to the constraints of the environments that organisms live in?

  3. What does an organism need to do? Stay alive (at least until reproduction)! The physiological systems that an organism has are adapted to this purpose.

  4. Generalized Animal Body Plan: How does each system contribute to homeostasis?

  5. Generalized PlantBody Plan What do each of the following do to maintain homeostasis? • root root tip/root hairs • shoot (stem) Nodes/internodes Buds Terminal/apical/axillary buds Flower buds & flowers • leaves mesophyll tissue/veins (vascular bundles)

  6. How does the environment influence an organism’s physiology? Tremendously! Natural selection will tend to drive the adaptation of physiology to environmental contstraints. This has resulted in a variety of mechanisms for maintaining homeostasis

  7. A Note About Plants: Plants have it a bit different: • They release almost no Nitrogenous waste. • Nitrogen is a limiting factor for plant growth in most soils. • They regulate osmolarity through transpiration. • Nitrogenous waste is an “animals only” problem. • Animals couple Nitrogenous waste excretion to osmolarity regulation.

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

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

  10. Animal systems evolved to support multicellular life aa O2 CH CHO CO2 aa NH3 CHO O2 CH O2 aa CO2 CO2 O2 NH3 aa NH3 CO2 NH3 CO2 CO2 NH3 NH3 O2 CO2 CO2 CO2 NH3 aa NH3 NH3 CHO CO2 CO2 aa CH intracellular waste extracellular waste Diffusion too slow!

  11. Overcoming limitations of diffusion CO2 CO2 O2 NH3 aa NH3 CO2 NH3 CO2 CO2 NH3 NH3 O2 CO2 CO2 CO2 NH3 aa NH3 NH3 CHO CO2 CO2 aa CH • Evolution of exchange systems for • distributing nutrients • circulatory system • removing wastes • excretory system systems to support multicellular organisms

  12. Osmoregulation hypotonic • Water balance • freshwater • hypotonic • water flow into cells & salt loss • saltwater • hypertonic • water loss from cells • land • dry environment • need to conserve water • may also need to conserve salt hypertonic Why do all land animals have to conserve water? • always lose water (breathing & waste) • may lose life while searching for water

  13. Intracellular Waste H O H | | | –C– C–OH N | H R Animalspoison themselvesfrom the insideby digestingproteins! • What waste products? • what do we digest our food into… • carbohydrates = CHO • lipids = CHO • proteins = CHON • nucleic acids = CHOPN  CO2 +H2O lots!  CO2 +H2O verylittle  CO2 +H2O + N  CO2 +H2O + P + N cellular digestion…cellular waste CO2 + H2O NH2= ammonia

  14. Nitrogenous waste disposal • Ammonia (NH3) • very toxic • carcinogenic • very soluble • easily crosses membranes • must dilute it & get rid of it… fast! • How you get rid of nitrogenous wastes depends on • who you are (evolutionary relationship) • where you live (habitat) aquatic terrestrial terrestrial egg layer

  15. 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

  16. 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

  17. Land animals H H H H N N C O • Nitrogen waste disposal on land • need to conserve water • must process ammonia so less toxic • urea = larger molecule = less soluble = less toxic • 2NH2 + CO2 = urea • produced in liver • kidney • 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 Ureacosts energyto synthesize,but it’s worth it! mammals

  18. Egg-laying land animals • Nitrogen waste disposal in egg • no place to get rid of waste in egg • need even less soluble molecule • uric acid = BIGGER = less soluble = less toxic • birds, reptiles, insects itty bittyliving space!

  19. Uric acid O O O N N N N H H H H And that folks, is why mostmale birds don’t have a penis! • Polymerized urea • large molecule • precipitates out of solution • doesn’t harm embryo in egg • white dust in egg • adults still excrete N waste as white paste • no liquid waste • uric acid = white bird “poop”!

  20. Mammalian System blood filtrate • Filter solutes out of blood & reabsorb H2O + desirable solutes • Key functions • Filtration: fluids (water & solutes) filtered outof blood • Reabsorption: selectively reabsorb (diffusion) needed water + solutes back to blood • Secretion: pump out any other unwanted solutes to urine • Excretion: expel concentrated urine (N waste + solutes + toxins) from body concentratedurine

  21. Mammalian Kidney inferiorvena cava aorta adrenal gland kidney nephron ureter renal vein& artery epithelialcells bladder urethra

  22. Nephron • Functional units of kidney • 1 million nephronsper kidney • Function • filter out urea & other solutes (salt, sugar…) • blood plasma filteredinto nephron • high pressure flow • selective reabsorption ofvaluable solutes & H2O back into bloodstream • greater flexibility & control whyselective reabsorption& not selectivefiltration? “counter current exchange system”

  23. Mammalian kidney How candifferent sectionsallow the diffusionof different molecules? • Interaction of circulatory & excretory systems • Circulatory system • glomerulus = ball of capillaries • Excretory system • nephron • Bowman’s capsule • loop of Henle • proximal tubule • descending limb • ascending limb • distal tubule • collecting duct Proximal tubule Distal tubule Bowman’s capsule Glomerulus Glucose H2O Na+ Cl- Amino acids H2O H2O Na+ Cl- H2O Mg++ Ca++ H2O H2O Collecting duct Loop of Henle

  24. Nephron: Filtration • At glomerulus • filtered out of blood • H2O • glucose • salts / ions • urea • not filtered out • cells • proteins high blood pressure in kidneysforce to push (filter) H2O & solutes out of blood vessel BIG problems when you start out with high blood pressure in systemhypertension = kidney damage

  25. Nephron: 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

  26. 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 • reabsorbed • H2O structure fitsfunction!

  27. Nephron: Re-absorption • Loop of Henle • ascending limb • low permeability to H2O • Cl- pump • Na+ follows by diffusion • different membrane proteins • reabsorbed • salts • maintains osmotic gradient structure fitsfunction!

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

  29. Nephron: Reabsorption & Excretion • Collecting duct • reabsorbed • H2O • excretion • concentrated urine passed to bladder • impermeable lining

  30. 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 the value of acounter current exchange system

  31. Summary whyselective reabsorption& not selectivefiltration? • Not filtered out • Cells, proteins • remain in blood (too big) • Reabsorbed: active transport • Na+Cl-, amino acids, glucose • Reabsorbed: diffusion • Na+, Cl–, H2O • Excreted • Urea, excess H2O , excess solutes (glucose, salts), toxins, drugs, “unknowns”

  32. Negative Feedback Loop high low 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

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

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

  35. 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

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

  37. Maintaining Water Balance adrenalgland • 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 Get morewater & salt intoblood fast! Why such arapid responsesystem? Spring a leak?

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

  39. Don’t get batty… Ask Questions!!

  40. Quick Check: Make Sure You Can • Explain the role of animal excretory systems in osmoregulation. • Compare the osmoregulatory approaches taken by conformers and regulators. • Label/Identify all organs that play major roles in the Excretory system. • Diagram all important parts of a nephron and explain their functions. • Diagram the feedback loops that function in regulating blood osmolarity. • Explain the causes of excretory system disruptions and how disruptions of the excretory system can lead to disruptions of homeostasis.

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