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Regulating the InternalEnvironment
Water Balance & Nitrogenous Waste
Removal
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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
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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
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intracellular waste
extracellular waste
Animal systems evolved to support multicellular life
O2
CHO
CHO
aa
aa
CH
CO2
NH3aa
O2
CH
O2
aa
CO2
CO2
CO2
CO2
CO2
CO2 CO2
CO2
CO2
CO2
NH3
NH3 NH3
NH3
NH3
NH3
NH3NH3
O2
aa
CH
aa
CHO
O2
Diffusion too slow!
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Overcoming limitations of diffusion• Evolution of exchange systems for
– distributing nutrients • Circulatory
– removing wastes• Excretory
systems to support multicellular organisms
systems to support multicellular organisms
aa
CO2
CO2
CO2
CO2
CO2
CO2 CO2
CO2
CO2
CO2
NH3
NH3 NH3
NH3
NH3
NH3
NH3NH3
O2
aa
CH
aa
CHO
O2
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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
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Intracellular Waste
• What waste products?– what do we digest our food into…
• carbohydrates = CHO• lipids = CHO• proteins = CHON • nucleic acids = CHOPN
CO2 + H2O
NH2 =
ammonia
CO2 + H2O CO2 + H2O
CO2 + H2O + N
CO2 + H2O + P + N
|
| ||H
HN C–OH
O
R
H–C–
lots!verylittle
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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
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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
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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
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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
OC
HNH
HNH
mammals
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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
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N
N N
N
O
HO
O
H
HH
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”!
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Mammalian System• Filter solutes out of blood &
reabsorb H2O + 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
blood filtrate
concentratedurine
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Mammalian Kidney
kidney
bladder
ureter
urethra
renal vein& artery
nephron
epithelialcells
adrenal glandinferior
vena cavaaorta
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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 & H2O back into bloodstream
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Mammalian kidney
Proximaltubule
Distal tubule
Glomerulus
Collecting ductLoop of Henle
Aminoacids
Glucose
H2O
H2O
H2O
H2O
H2O
H2O
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-
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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 transportwherever possible
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Any Questions?
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Regulating the InternalEnvironment
Maintaining Homeostasis
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sensor
Negative Feedback Loop
high
low
hormone or nerve signal
lowersbody condition(return to set point)
hormone or nerve signal
gland or nervous system
raisesbody condition (return to set point)
gland or nervous system
sensor
specific body condition
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Controlling Body Temperature
high
low
nerve signals
sweat
nerve signals
body temperature
shiver brain
dilates surfaceblood vessels
constricts surfaceblood vessels
Nervous System Control
brain
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nephron
low
Blood Osmolarity
blood osmolarityblood pressure
ADH
increasedwater
reabsorption
increasethirst
high
Endocrine System Control
pituitary
ADH = AntiDiuretic Hormone
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H2O
H2O
H2O
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
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low
Blood Osmolarity
blood osmolarityblood pressure
increasedwater & saltreabsorption
in kidney
high
Endocrine System Control
angiotensigenangiotensin
nephronadrenalgland
aldosterone
JGA
JGA = JuxtaGlomerular Apparatus
rennin
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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 & H2O in kidneys• puts more water & salts back in blood adrenal
gland
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nephron
low
Blood Osmolarity
blood osmolarityblood pressure
ADH
increasedwater
reabsorption
increasethirst
renin
increasedwater & saltreabsorption
high
Endocrine System Control
pituitary
angiotensinogenangiotensin
nephronadrenalgland
aldosterone
JuxtaGlomerularApparatus
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Don’t get batty…
Ask Questions!!