Regulating the Internal Environment AP Biology 2006 -2007

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

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

Regulating the Internal Environment Water Balance & Nitrogenous Waste Removal AP Biology 2006 -2007

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

Overcoming limitations of diffusion § Evolution of exchange systems for distributing nutrients § circulatory system u removing wastes § excretory system u aa AP Biology aa CH NH 3 CO 2 NH 3 O 2 NH 3 CO 2 systems to support multicellular organisms CO 2 NH 3 CO 2 aa CHO

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

Intracellular Waste § What waste products? u what do we digest our food into… § § carbohydrates = CHO CO 2 + H 2 O lots! lipids = CHO CO 2 + H 2 O proteins = CHON CO 2 + H 2 O + N nucleic acids = CHOPN CO 2 + H 2 O + P + N cellular digestion… cellular waste NH 2 = AP Biology ammonia Animals poison themselves from the inside by digesting proteins! H O | || H N –C– C–OH | H R very little CO 2 + H 2 O

Nitrogenous waste disposal § Ammonia (NH 3) u very toxic § carcinogenic u very soluble § easily crosses membranes u must dilute it & get rid of it… fast! § How you get rid of nitrogenous wastes depends on u who you are (evolutionary relationship) u where you live (habitat) aquatic AP Biology terrestrial egg layer

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

Freshwater animals § Water removal & nitrogen waste disposal u remove surplus water § use surplus water to dilute ammonia & excrete it w 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 u overcome loss of salts § reabsorb in kidneys or active transport across gills AP Biology

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

Egg-laying land animals § Nitrogen waste disposal in egg no place to get rid of waste in egg u need even less soluble molecule u § uric acid = BIGGER = less soluble = less toxic u birds, reptiles, insects itty bitty living space! AP Biology

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

Mammalian System blood filtrate § Filter solutes out of blood & § reabsorb H 2 O + desirable solutes Key functions u filtration § fluids (water & solutes) filtered out of blood u reabsorption § selectively reabsorb (diffusion) needed water + solutes back to blood u secretion § pump out any other unwanted solutes to urine u excretion § expel concentrated urine (N waste + solutes + toxins) from body AP Biology concentrated urine

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

Nephron § Functional units of kidney u 1 million nephrons per kidney § Function u u filter out urea & other solutes (salt, sugar…) blood plasma filtered into nephron § high pressure flow u AP Biology selective reabsorption of valuable solutes & H 2 O back into bloodstream § greater flexibility & control why selective reabsorption & not selective filtration? “counter current exchange system”

How can different sections allow the diffusion of different molecules? Mammalian kidney § Interaction of circulatory § & excretory systems Circulatory system u glomerulus = ball of capillaries Bowman’s capsule Proximal tubule Distal tubule Glomerulus § Excretory system u u u nephron Bowman’s capsule loop of Henle § § u AP Biology proximal tubule descending limb ascending limb distal tubule collecting duct Glucose Amino acids H 2 O Mg++ Ca++ H 2 O Na+ Cl. H 2 O Loop of Henle Collecting duct

Nephron: Filtration § At glomerulus u filtered out of blood § § u H 2 O glucose salts / ions urea not filtered out § cells § proteins AP Biology high blood pressure in kidneys force to push (filter) H 2 O & solutes out of blood vessel BIG problems when you start out with high blood pressure in system hypertension = kidney damage

Nephron: Re-absorption § Proximal tubule u reabsorbed back into blood § Na. Cl w active transport of Na+ w Cl– follows by diffusion § H 2 O § glucose § HCO 3 w bicarbonate w buffer for AP Biology blood p. H Descending limb Ascending limb

Nephron: Re-absorption structure fits § Loop of Henle function! u descending limb § high permeability to H 2 O w many aquaporins in cell membranes § low permeability to salt w few Na+ or Cl– channels u reabsorbed § H 2 O AP Biology Descending limb Ascending limb

Nephron: Re-absorption structure fits § Loop of Henle function! u ascending limb § low permeability to H 2 O § Cl- pump § Na+ follows by diffusion w different membrane proteins u reabsorbed § salts w maintains osmotic AP Biology gradient Descending limb Ascending limb

Nephron: Re-absorption § Distal tubule u reabsorbed § salts § H 2 O § HCO 3 w bicarbonate AP Biology

Nephron: Reabsorption & Excretion § Collecting duct u reabsorbed § H 2 O u excretion § concentrated urine passed to bladder w impermeable lining AP Biology Descending limb Ascending limb

Osmotic control in nephron § How is all this re-absorption achieved? tight osmotic control to reduce the energy cost of excretion u use diffusion instead of active transport wherever possible u the value of a counter current exchange system AP Biology

why selective reabsorption & not selective filtration? Summary § Not filtered out u u cells u proteins remain in blood (too big) § Reabsorbed: active transport u u Na+ Cl– amino acids u glucose u § Reabsorbed: diffusion u u Na+ H 2 O u Cl– § Excreted u u AP Biologyu urea excess H 2 O u excess solutes (glucose, salts) toxins, drugs, “unknowns”

Any Questions? AP Biology 2006 -2007

Regulating the Internal Environment Maintaining Homeostasis AP Biology 2006 -2007

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

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

Endocrine System Control Blood Osmolarity ADH pituitary increased water reabsorption nephron high blood osmolarity blood pressure AP Biology increase thirst low ADH = Anti. Diuretic Hormone

Maintaining Water Balance § High blood osmolarity level u too many solutes in blood Get more water into blood fast § dehydration, high salt diet u u stimulates thirst = drink more release ADH from pituitary gland § antidiuretic hormone u increases permeability of collecting duct & reabsorption of water in kidneys H 2 O § increase water absorption back into blood § decrease urination AP Biology Alcohol suppresses ADH… makes you urinate a lot! H 2 O

Endocrine System Control Blood Osmolarity Oooooh, zymogen! JGA = Juxta. Glomerular Apparatus high blood osmolarity blood pressure adrenal gland increased water & salt reabsorption in kidney JGA nephron renin aldosterone AP Biology low angiotensinogen

Maintaining Water Balance § Low blood osmolarity level or low blood pressure u u u Get more water & salt into blood fast! JGA releases renin in kidney renin converts angiotensinogen to angiotensin causes arterioles to constrict § increase blood pressure u u angiotensin triggers release of aldosterone from adrenal gland increases reabsorption of Na. Cl & H 2 O in kidneys § puts more water & salts back in blood AP Biology Why such a rapid response system? Spring a leak? adrenal gland

Endocrine System Control Blood Osmolarity ADH increased water reabsorption pituitary nephron high blood osmolarity blood pressure adrenal gland increased water & salt reabsorption low Juxta. Glomerular Apparatus nephron renin aldosterone AP Biology increase thirst angiotensinogen

Don’t get batty… Ask Questions!! AP Biology 2006 -2007