Transcript Regulating the Internal Environment

Endocrine System, Feedback
loops, & Digestive System
AP Biology
2006-2007
Osmoregulation
hypotonic
 Water balance

freshwater
 hypotonic
 water flow into cells & salt loss

saltwater
 hypertonic
 water loss from cells

hypertonic
land
 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)
AP
may
lose life while searching for water
Biology
Intracellular Waste
 What waste products?

Animals
poison themselves
from the inside
by digesting
proteins!
what do we digest our food into…
 carbohydrates = CHO  CO2 + H2O
 lipids = CHO  CO2 + H2O
lots!
 proteins = CHON  CO2 + H2O + N
very
little
 nucleic acids = CHOPN  CO2 + H2O + P + N
cellular digestion…
cellular waste
NH2 =
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ammonia
H| O
||
H
N –C– C–OH
|
H
R
CO2 + H2O
Nitrogenous waste disposal
 Ammonia (NH3)

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
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terrestrial
terrestrial egg layer
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
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 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
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H
Land animals
 Nitrogen waste disposal on land
H
H
H
need to conserve water
 must process ammonia so less toxic

N
C
O
N
 urea = larger molecule = less soluble = less toxic
 2NH2 + CO2 = urea
Urea
 produced in liver
costs energy

kidney
to synthesize,
but it’s worth it!
 filter solutes out of blood
 reabsorb H2O (+ any useful solutes)
 excrete waste
 urine = urea, salts, excess sugar & H2O

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
urine is very concentrated
concentrated NH3 would be too toxic
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
itty bitty
living space!
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
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Uric acid
 Polymerized urea
And that folks,
is why most
male birds don’t
have a penis!
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”!
O
H
H
N
N
O
O
N
N
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H
H
Mammalian System
 Filter solutes out of blood &
blood
filtrate
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

excretion
 expel concentrated urine (N waste +
AP Biology
solutes + toxins) from body
concentrated
urine
why
selective reabsorption
& not selective
filtration?
Summary
 Not filtered out


cells
 proteins
remain in blood (too big)
 Reabsorbed: active transport


Na+
Cl–
amino acids
 glucose

 Reabsorbed: diffusion


Na+
H2O

Cl–
 Excreted


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urea
excess H2O
 excess solutes (glucose, salts)
toxins, drugs, “unknowns”
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)
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low
hormone or nerve signal
Nervous System Control
Controlling Body Temperature
nerve signals
brain
sweat
high
body temperature
low
brain
constricts surface shiver
blood vessels
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nerve signals
dilates surface
blood vessels
Endocrine System Control
Blood Osmolarity
ADH
pituitary
increased
water
reabsorption
increase
thirst
nephron
high
blood osmolarity
blood pressure
low
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ADH =
AntiDiuretic Hormone
Endocrine System Control
Blood Osmolarity
Oooooh,
zymogen!
JGA =
JuxtaGlomerular
Apparatus
high
blood osmolarity
blood pressure
adrenal
gland
low
increased
water & salt
reabsorption
in kidney
nephron
renin
aldosterone
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JGA
angiotensinogen
angiotensin
Digestive System
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Gastrovascular Cavities
 Gastrovascular

cavities are the
digestive systems in
simple animals
(Cnidarians,
Platyhelminthes)
Incomplete
Digestive Systemone opening
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Digestion in Alimentary Canals
 Complex animals
An “Entrance” and an “Exit”
 This is a complete digestive system.

 Mouth = site of ingestion
 Anus = site of elimination
 What phyla have complete digestive

tracts?
(Nematoda, Mollusca, Annelida,
Arthropoda, Echinodermata, Chordata)
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Alimentary Canals/Complete
Digestive System
AP Biology
INTESTINAL LUMEN
Absorption
Mechanisms
carbohydrates
monosaccharides
Monosaccharides &
amino acids are
proteins
actively transported
across plasma
EPITHELIAL
CELL
membrane of
epithelial cells, then
from cell into
internal environment
AP Biology
Figure 41.11
Page 734
INTERNAL
ENVIRONMENT
amino acids