Regulating the Internal Environment Water Balance & Nitrogenous Waste Removal

Conformers vs. Regulators Two evolutionary paths for organisms –Endothermy maintain relatively constant internal conditions –Ectothermy allow internal conditions to fluctuate along with external changes conformer thermoregulation regulator conformer osmoregulation regulator

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

intracellular waste extracellular waste Animal systems evolved to support multicellular life O2O2 CHO aa CH CO 2 NH 3 aa O2O2 CH O2O2 aa CO 2 NH 3 O2O2 aa CH aa CHO O2O2 Diffusion too slow!

Overcoming limitations of diffusion Evolution of exchange systems for –distributing nutrients Circulatory –removing wastes Excretory systems to support multicellular organisms aa CO 2 NH 3 O2O2 aa CH aa CHO O2O2

Osmoregulation Why do all land animals have to conserve water? 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

Intracellular Waste What waste products? –what do we digest our food into… carbohydrates = CHO lipids = CHO proteins = CHON nucleic acids = CHOPN CO 2 + H 2 O NH 2 = ammonia  CO 2 + H 2 O  CO 2 + H 2 O + N  CO 2 + H 2 O + P + N | ||| H H N C–OH O R H –C– lots! very little

Nitrogenous waste disposal Ammonia (NH 3 ) –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) aquaticterrestrialterrestrial egg layer

Nitrogen waste Aquatic animals –can afford to lose water –_Ammonia_______ most toxic Terrestrial Animals –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 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

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 + CO 2 = urea –produced in liver –Kidney_______ filter solutes out of blood reabsorb H 2 O (+ any useful solutes) excrete waste –Urine = urea, salts, excess sugar & H 2 O »urine is very concentrated »concentrated NH 3 would be too toxic O C H N H H N H mammals

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

N N N N O H O O H H H Uric acid Polymerized urea –large molecule –Requires more energy to make –Relatively non-toxic doesn’t harm embryo in egg –white dust in egg adults excrete N waste as white paste –no liquid waste –urea = white bird “poop”!

Mammalian System Filter solutes out of blood & reabsorb H 2 O + 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 –Excreation expel concentrated urine (N waste + solutes + toxins) from body bloodfiltrate concentrated urine

Mammalian Kidney kidney bladder ureter urethra renal vein & artery nephron epithelial cells adrenal gland inferior vena cava aorta

Nephron Functional units of kidney –1 million nephrons per kidney Function –filter out urea & other solutes (salt, sugar…) –Blood pressure forces blood into nephron high pressure flow –Proximal tubule, loop of Henle and distal tubule reabsorb valuable solutes & H 2 O back into bloodstream

Mammalian kidney Proximal tubule Distal tubule Glomerulus Collecting duct Loop of Henle Amino acids Glucose H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O Na + Cl - Mg ++ Ca ++ Interaction of circulatory & excretory systems Circulatory system –Glomerulus = ball of capillaries Excretory system –Bowman’s capsule –Proximal tubule –Loop of Henle descending limb ascending limb –Distal tubule –Collecting duct Bowman’s capsule Na + Cl -

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

Any Questions?

Regulating the Internal Environment Maintaining Homeostasis

sensor Negative Feedback Loop high low hormone or nerve signal lowers body condition (return to set point) hormone or nerve signal gland or nervous system raises body condition (return to set point) gland or nervous system sensor specific body condition

Controlling Body Temperature high low nerve signals sweat nerve signals body temperature shiver brain dilates surface blood vessels constricts surface blood vessels Nervous System Control brain

nephron low Blood Osmolarity blood osmolarity blood pressure ADH increased water reabsorption increase thirst high Endocrine System Control pituitary ADH = AntiDiuretic Hormone

H2OH2O H2OH2O H2OH2O Maintaining Water Balance 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

low Blood Osmolarity blood osmolarity blood pressure increased water & salt reabsorption in kidney high Endocrine System Control angiotensigen angiotensin nephron adrenal gland aldosterone JGA JGA = JuxtaGlomerular Apparatus rennin

Maintaining Water Balance 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 & H 2 O in kidneys puts more water & salts back in blood adrenal gland

nephron low Blood Osmolarity blood osmolarity blood pressure ADH increased water reabsorption increase thirst renin increased water & salt reabsorption high Endocrine System Control pituitary angiotensinogen angiotensin nephron adrenal gland aldosterone JuxtaGlomerular Apparatus

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