Water Balance & Nitrogenous Waste Removal

1. Water Balance & Nitrogenous Waste Removal Kidney Function

2. 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 Animal systems evolved to support multicellular life intracellular waste extracellular waste Diffusion too slow!

3. 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 Overcoming limitations of diffusion • Evolution of exchange systems for systems to support multicellular organisms

4. Osmoregulation • Water balance vs. habitat Why doall land animalshave to conservewater?

5. H O H | | | –C– C–OH N | H R Animalspoison themselvesfrom the insideby digestingproteins! Intracellular Waste • 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

6. Nitrogenous waste disposal • Ammonia (NH3) • _________________________ • carcinogenic • _________________________ • 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

8. Freshwater animals • Hypotonic environment • water diffuses into cells • Manage water & waste together • remove surplus water & waste • use surplus water to dilute ammonia & excrete it • also diffuse ammonia continuously through gills • overcome loss of salts • reabsorb in kidneys or active transport across gills

9. H H H H N N C O Land animals • 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

10. 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!

11. O O O N N N N H H H H And that folks, is why mostmale birds don’t have a penis! Uric acid • 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 • white bird “poop” = uric acid paste!

12. Mammalian System blood filtration • Filter solutes out of blood & reabsorb H2O + desirable solutes • Key functions filtrate reabsorption secretion excretion urine

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

14. 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”

15. How candifferent sectionsallow the diffusionof different molecules? Mammalian kidney • Interaction of circulatory & excretory systems • Circulatory system • _________________ = ball of capillaries • Excretory system • _________________ • _________________ • _________________ • proximal tubule • descending limb • ascending limb • distal tubule • _________________ 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

16. Nephron: Filtration • At glomerulus • filtered out of blood • ______________ • ______________ • ______________ • ______________ • not filtered out • ______________ • ______________ 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

17. Descendinglimb Ascendinglimb Nephron: Re-absorption • Proximal tubule • reabsorbed back into blood • ________________ • ________________ • ________________ • ________________

18. Descendinglimb Ascendinglimb Nephron: Re-absorption structure fitsfunction! • Loop of Henle • descending limb • reabsorbed • ___________________ • structure

19. Descendinglimb Ascendinglimb Nephron: Re-absorption structure fitsfunction! • Loop of Henle • ascending limb • reabsorbed • ___________________ • structure

20. Nephron: Re-absorption • Distal tubule • reabsorbed • ______________ • ______________ • ______________ • HCO3- • regulate blood pH

21. Descendinglimb Ascendinglimb Nephron: Reabsorption & Excretion • Collecting duct • reabsorbed • ________________ • excretion • ________________ • to bladder

22. 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

23. Recap…

24. whyselective reabsorption& not selectivefiltration? 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”

25. Maintaining Homeostasis

26. 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

27. increasethirst pituitary nephron high low Endocrine System Control Water Balance: Blood Osmolarity ADH increasedwaterreabsorption blood osmolarity blood pressure/volume ADH = AntiDiuretic Hormone

28. Maintaining Water Balance Get morewater intoblood • High blood osmolarity level • too many solutes in blood • dehydration, high salt diet • triggers release antidiuretic hormone(ADH) • produced in hypothalamus • stored in pituitary • makes collecting duct more permeabilityto water • increase water absorption back into blood • more concentrated urine; decrease urination H2O H2O Alcohol suppresses ADH… makes youurinate a lot! H2O

29. high low JGA adrenalgland nephron Endocrine System Control Blood Pressure / Volume Oooooh,zymogen! JGA = JuxtaGlomerular Apparatus blood osmolarity blood pressure/volume increasedwater & saltreabsorption renin aldosterone angiotensinogen angiotensin

30. adrenalgland Maintaining Water Balance Get morewater & salt intoblood fast! • Low blood volume or low blood pressure • JGA releases renin which acts as an enzyme • activates angiotensinogenangiotensin • angiotensin acts as a hormone • causes arterioles to constrict = raises blood pressure • triggers release of aldosterone from adrenal gland • aldosterone acts as a hormone • increases kidney reabsorption of Na+ & H2O • puts more water & salts back in blood Why such arapid response system? Spring a leak?

31. increasethirst pituitary nephron high JuxtaGlomerularApparatus low adrenalgland nephron Endocrine System Control Water Balance ADH increasedwaterreabsorption blood osmolarity blood pressure/volume increasedwater & saltreabsorption renin aldosterone angiotensinogen angiotensin

32. Don’t get batty… Ask Questions!!