Chapter 44 Regulating the Internal Environment AP Biology

Chapter 44. Regulating the Internal Environment AP Biology 2005 -2006

Homeostasis § Living in the world organisms had a choice: u regulate their internal environment § maintain relatively constant internal conditions u conform to the external environment § allow internal conditions to fluctuate along with external changes reptiles fluctuate with external conditions AP Biology mammals internally regulate 2005 -2006

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 & waste disposal nutrients ion balance cell growth maintaining a “steady state” condition 2005 -2006

Homeostasis § Osmoregulation u solute balance & gain or loss of water § Excretion u elimination of nitrogenous wastes § Thermoregulation u AP Biology maintain temperature within tolerable range 2005 -2006

Chapter 44. Regulating the Internal Environment Water Balance AP Biology 2005 -2006

AP Biology 2005 -2006

Unicellular Multi-cellular Warm, dilute ocean waters • All cells in direct contact with environment • Direct exchange of nutrients & waste with environment AP Biology Warm, dilute ocean waters • Internal cells no longer in direct contact with environment • Must solve exchange problem • Have to maintain the “internal ocean” 2005 -2006

What are the issues? Warm, dilute ocean waters CH aa O 2 CH 2 O O 2 CO 2 NH 3 CH O 2 aa CH 2 O Warm, dilute ocean waters CH O 2 CH 2 O aa O 2 aa CO 2 CH 2 O CH O 2 NH 3 CH 2 O O 2 CO 2 NH CO 2 3 CO 2 NH 3 CO 2 CO NH 3 2 CO 2 CH CO NH 3 2 CH 2 O aa Diffusion is not adequate for moving material across more than 1 cell barrier AP Biology 2005 -2006

Solving exchange problem § Had to evolve exchange systems for: distributing nutrients § circulatory system u removing wastes § excretory system u Warm, dilute ocean waters overcoming the limitations of diffusion AP Biology 2005 -2006

Osmoregulation § Water balance u freshwater = hypotonic § manage water moving into cells § salt loss u saltwater = hypertonic § manage water loss from cells § salt accumulation u land § manage water loss § need to conserve water Why do all land animals have to conserve water? • always need water for life • always lose water (breathing & waste) • may lose life while searching for water AP Biology 2005 -2006

Water & salt… § Salt secreting glands of marine birds remove salt from blood allowing them to drink sea water during months at sea u secrete a fluid much more salty than ocean water How does structure of epithelial cells govern water regulation? § different proteins in membranes § sea birds pump salt out of blood § freshwater fish pump salts into blood from water AP Biology 2005 -2006

Waste disposal § What waste products? u Animals can’t store proteins what do we breakdown? § § carbohydrates = CHO CO 2 + H 2 O 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 w relatively small amount in cell NH 2 = AP Biology ammonia H| OH || H N –C– C–OH | H R CO 2 + H 2 O 2005 -2006

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 N-wastes depends on u who you are (evolutionary relationship) u where you live (habitat) AP Biology 2005 -2006

N waste § Ammonia u u most toxic freshwater organisms § Urea u u less toxic terrestrial § Uric acid u u u AP Biology least toxic egg layers most water conservative 2005 -2006

Freshwater animals § Nitrogen waste disposal in water u if you have a lot of water you can dilute ammonia then excrete § freshwater fish pass ammonia continuously through gills w need to excrete a lot of water anyway so excrete very dilute urine § freshwater invertebrates pass ammonia through their whole body surface AP Biology 2005 -2006

Land animals § Nitrogen waste disposal on land u evolved less toxic waste product § need to conserve water § urea = less soluble = less toxic u kidney § filter wastes out of blood § reabsorb H 2 O § excrete waste w urine = urea, salts, excess sugar & H 2 O n n AP Biology urine is very concentrated NH 3 would be too toxic 2005 -2006

Urea § 2 NH 2 + CO 2 = urea u combined in liver § Requires energy H N to produce u worth the investment of energy § Carried to kidneys by circulatory system AP Biology H H C N H 2005 -2006 O

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 = less soluble = less toxic u AP Biology birds, reptiles, insects 2005 -2006

Uric acid § Polymerized urea And that folks… is why a male bird doesn’t have… a penis! large molecule u precipitates out of solution u § doesn’t harm embryo in egg w white dust in egg § adults excrete white paste w no liquid waste w white bird poop! AP Biology 2005 -2006

Mammalian System § Key functions u filtration § body fluids (blood) collected § water & soluble material removed u reabsorption § reabsorb needed substances back to blood u secretion § pump out unwanted substances to urine u excretion § remove excess substances & toxins from body AP Biology 2005 -2006

Mammalian kidney § Urinary system filters blood & helps maintain water balance (osmoregulation) u u pair of bean-shaped kidneys supplied with blood § renal artery § renal vein AP Biology 2005 -2006

AP Biology 2005 -2006

Mammalian Kidney AP Biology 2005 -2006

Kidney & Nephron nephron AP Biology 2005 -2006

Nephron § Functional units of kidney u 1 million nephrons per kidney § Function u remove urea & other solutes (salt, sugar…) § Process u u AP Biology liquid of blood (plasma) filtered into nephron selective recovery of valuable solutes that’s called a “counter current exchange system” 2005 -2006

Mammalian kidney § Interaction of circulatory & § excretory systems Circulatory system u glomerulus = ball of capillaries § Excretory system u u u nephron Bowman’s capsule loop of Henle § descending limb § ascending limb u AP Biology collecting duct 2005 -2006

Nephron: Filtration § Filtered out H 2 O u glucose u salts / ions u urea u § Not filtered out cells u proteins u AP Biology 2005 -2006

Nephron: Re-absorption § Proximal tubule u reabsorbed § Na. Cl w active transport Na+ w Cl- follows by diffusion § H 2 O § glucose § HCO 3 w bicarbonate w buffer for Descending limb Ascending limb blood p. H AP Biology 2005 -2006

Nephron: Re-absorption § Loop of Henle u descending limb § many aquaporins in cell membranes § high permeability to H 2 O § low permeability to salt u structure fits function! Descending limb Ascending limb reabsorbed § H 2 O AP Biology 2005 -2006

Nephron: Re-absorption § Loop of Henle u structure fits function! ascending limb § low permeability to H 2 O § Cl- pump § Na+ follows by diffusion u reabsorbed Descending limb Ascending limb § salts w maintains osmotic gradient AP Biology 2005 -2006

Nephron: Re-absorption § Distal tubule u reabsorbed § salts § H 2 O § HCO 3 w bicarbonate AP Biology 2005 -2006

Nephron: Reabsorption & Excretion § Collecting duct u reabsorbed § H 2 O u excretion § urea passed through to bladder AP Biology 2005 -2006

Osmotic control in nephron § How is all this re-absorption achieved? tight osmotic control to reduce the energy cost of excretion u as much as possible, use diffusion instead of active transport u AP Biology 2005 -2006

Summary § Not filtered out (remain in blood) u cells u proteins § Reabsorbed: active transport u u Na+ Cl- amino acids u glucose u § Reabsorbed: diffusion u Na+ u Cl- § Reabsorbed: osmosis u H 2 O § Excreted u u AP Biology urea u H 2 O any excess solutes 2005 -2006

Maintaining Water Balance § Monitor blood osmolarity u amount of dissolved material in blood High solutes in brain AP Biology ADH = anti-diuretic hormone 2005 -2006

Maintaining Water Balance § High blood osmolarity level u too many solutes in blood Get more water into blood fast § dehydration, salty foods u u release ADH (anti-diuretic hormone) from pituitary (in brain) increases permeability of collecting duct & reabsorption of water in kidneys § increase water absorption back into blood § decrease urination u also stimulates thirst = drink more Alcohol inhibits ADH… makes you urinate a lot! AP Biology 2005 -2006

Maintaining Water Balance § Low blood osmolarity level or low blood pressure Oooh… zymogen ! Low solutes renin activates angiotensinogen angiotensin triggers aldosterone increases absorption of & H 2 O in kidney AP Na. Cl Biology 2005 -2006

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? 2005 -2006