Regulating the Internal Environment Water Balance & Nitrogenous Waste Removal

Transcription

1 Regulating the Internal Environment Water Balance & Nitrogenous Waste Removal Animal systems evolved to support multicellular life CH CHO O 2 O 2 NH 3 CH CHO O 2 CO 2 NH NH 3 O 2 3 NH 3 intracellular waste O 2 NH 3 NH3 NH 3 NH 3 NH 3 CHO CH Diffusion too slow! extracellular waste 1

2 Overcoming limitations of diffusion Evolution of exchange systems for distributing nutrients circulatory system removing wastes excretory system CO 2 NH NH 3 O 2 3 NH 3 systems to support multicellular organisms O 2 CH NH 3 NH3 NH 3 NH 3 NH 3 CHO Osmoregulation 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 hypotonic hypertonic Why do all land animals have to conserve water? always lose water (breathing & waste) AP may Biology lose life while searching for water 2

3 Intracellular Waste What waste products? Animals poison themselves from the inside by digesting proteins! what do we digest our food into carbohydrates = CHO + lipids = CHO + proteins = CHON + + N lots! nucleic acids = CHOPN + + P + N very little cellular digestion cellular waste NH 2 = ammonia H O H H N C C OH R + Nitrogenous waste disposal Ammonia (NH 3 ) 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 3

4 Nitrogen waste Aquatic organisms can afford to lose water ammonia most toxic Terrestrial need to conserve water urea less toxic Terrestrial egg layers need to conserve water need to protect embryo in egg uric acid least toxic 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 4

5 Land animals Nitrogen waste disposal on land need to conserve water must process ammonia so less toxic urea = larger molecule = less soluble = less toxic 2NH 2 + = urea Urea produced in liver costs energy kidney to synthesize, but it s worth it! filter solutes out of blood reabsorb (+ any useful solutes) excrete waste urine = urea, salts, excess sugar & urine is very concentrated concentrated NH 3 would be too toxic mammals HH N HH N C O 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 bitty living space! 5

6 H N O Uric acid O N H 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! H N N H O And that folks, is why most male birds don t have a penis! Mammalian System Filter solutes out of blood & reabsorb + desirable solutes Key functions filtration fluids (water & solutes) filtered out of 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 blood filtrate concentrated urine 6

7 Mammalian Kidney inferior vena cava aorta adrenal gland kidney ureter bladder urethra renal vein & artery nephro n epithelial cells Nephron Functional units of kidney 1 million nephrons per kidney Function filter out urea & other solutes (salt, sugar ) blood plasma filtered into nephron high pressure flow selective reabsorption of valuable solutes & back into bloodstream greater flexibility & control why selective reabsorption & not selective filtration? counter current exchange system 7

8 Mammalian kidney Interaction of circulatory & excretory systems Circulatory system glomerulus = ball of capillaries Excretory system nephron Bowman s capsule loop of Henle proximal tubule descending ascending distal tubule collecting duct Glomerulus Bowman s capsule How can different sections allow the diffusion of different molecules? Glucose Amino acids Mg ++ Ca ++ Proximal tubule Loop of Henle Na + Cl - Na + Cl - Distal tubule Collecting duct Nephron: Filtration At glomerulus filtered out of blood glucose salts / ions urea not filtered out cells proteins high blood pressure in kidneys force to push (filter) & solutes out of blood vessel BIG problems when you start out with high blood pressure in system hypertension = kidney damage 8

9 Nephron: Re-absorption Proximal tubule reabsorbed back into blood NaCl active transport of Na + Cl follows by diffusion glucose HCO 3 - bicarbonate buffer for blood ph Descending Ascending Nephron: Re-absorption Loop of Henle descending high permeability to many aquaporins in cell membranes low permeability to salt few Na + or Cl channels reabsorbed Descending structure fits function! Ascending 9

10 Nephron: Re-absorption Loop of Henle ascending low permeability to Cl - pump Na + follows by diffusion different membrane proteins reabsorbed salts maintains osmotic gradient Descending structure fits function! Ascending Nephron: Re-absorption Distal tubule reabsorbed salts HCO 3 - bicarbonate 10

11 Nephron: Reabsorption & Excretion Collecting duct reabsorbed excretion concentrated urine passed to bladder impermeable lining Descending Ascending Osmotic control in nephron How is all this re-absorption achieved? tight osmotic control to reduce the energy cost of excretion use diffusion instead of active transport wherever possible the value of a counter current exchange system 11

12 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 Excreted urea why selective reabsorption & not selective filtration? excess u excess solutes (glucose, salts) toxins, drugs, unknowns Any Questions?

13 Regulating the Internal Environment Maintaining Homeostasis Negative Feedback Loop hormone or nerve signal gland or nervous system lowers body condition (return to set point) high sensor specific body condition sensor low raises body condition (return to set point) gland or nervous system hormone or nerve signal 13

14 Nervous System Control Controlling Body Temperature nerve signals brain sweat high body temperature low dilates surface blood vessels constricts surface blood vessels shiver brain nerve signals Endocrine System Control Blood Osmolarity Oooooh, zymogen! adrenal gland high increased water & salt reabsorption in kidney aldosterone blood osmolarity blood pressure angiotensin low nephron renin JGA = JuxtaGlomerular Apparatus JGA angiotensinogen 14

15 Maintaining Water Balance 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 permeability to water increase water absorption back into blood more concentrated urine; decrease urination Alcohol suppresses ADH makes you urinate a lot! Get more water into blood Endocrine System Control Blood Pressure / Volume Oooooh, zymogen! adrenal gland JGA = JuxtaGlomerular high Apparatus blood osmolarity blood pressure/volume low JGA increased water & salt nephron reabsorption renin aldosterone angiotensinogen angiotensin 15