Transcript Regulating the Internal Environment

Water Balance &
Nitrogenous Waste Removal
Kidney Function
AP Biology
2009-2010
Animal systems evolved to
support multicellular life
aa
O2
CH
CHO
CO2
aa
NH3
CHO
O2
O2
CH
aa
CO2
aa
NH3
CO2
NH3
CH
CO2
CO2
NH3
NH3
CO2
AP Biology
NH3
NH3
CO2
CO2
aa
O2
NH3
NH3
CO2
O2
intracellular
waste
CO2
CHO
CO2
aa
Diffusion too slow!
extracellular
waste
Overcoming limitations of diffusion
 Evolution of exchange systems for
CO2
CO2
aa
CO2
CO2
O2
NH3
CO2
NH3
CH
CO2
CO2
NH3
NH3
CO2
systems to support
organisms
AP multicellular
Biology
NH3
NH3
CO2
aa
O2
NH3
NH3
CHO
CO2
aa
Osmoregulation
 Water balance vs. habitat
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Why do
all land animals
have to conserve
water?
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 =
AP Biology
ammonia
H| O
||
H
N –C– C–OH
|
H
R
CO2 + H2O
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
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terrestrial
terrestrial egg layer
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Freshwater animals
 Hypotonic environment

water diffuses into cells
 Manage water & waste together

remove surplus water & waste
 use surplus water to dilute ammonia & excrete it
 also diffuse ammonia continuously through gills

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
 white bird “poop” =
H
uric acid paste!
O
H
N
N
O
O
N
N
AP Biology
H
H
Mammalian System
blood
filtration
 Filter solutes out of blood &
reabsorb H2O + desirable solutes
 Key functions
filtrate
reabsorption
secretion
excretion
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urine
Mammalian Kidney
inferior
vena cava
aorta
adrenal gland
kidney
ureter
bladder
urethra
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nephro
n
renal vein
& artery
epithelial
cells
Nephron
 Functional units of kidney

1 million nephrons
per kidney
 Function


filter out urea & other
solutes (salt, sugar…)
blood plasma filtered
into nephron
 high pressure flow

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selective reabsorption of
valuable solutes & H2O
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

Bowman’s
capsule
_________________Glomerulus
=
ball of capillaries
Proximal
tubule
Distal
tubule
 Excretory system



_________________
_________________
_________________





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proximal tubule
descending limb
ascending limb
distal tubule
_________________
Glucose
Amino
acids
H2O
Mg++ Ca++
H2O
Na+ ClH2O
H2O
Na+ Cl-
H2O
H2O
Loop of Henle
Collecting
duct
Nephron: Filtration
 At glomerulus

filtered out of blood
 ______________
 ______________
 ______________
 ______________

not filtered out
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high blood pressure in kidneys
 ______________ force to push (filter) H2O & 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

reabsorbed back into blood
 ________________
 ________________
 ________________
 ________________
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Descending
limb
Ascending
limb
Nephron: Re-absorption
 Loop of Henle
structure fits
function!
descending limb
 reabsorbed

 ___________________

structure
Descending
limb
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Ascending
limb
Nephron: Re-absorption
 Loop of Henle
structure fits
function!
ascending limb
 reabsorbed

 ___________________

structure
Descending
limb
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Ascending
limb
Nephron: Re-absorption
 Distal tubule

reabsorbed
 ______________
 ______________
 ______________
 HCO3 regulate blood pH
AP Biology
Nephron: Reabsorption & Excretion
 Collecting duct

reabsorbed
 ________________

excretion
 ________________
 to bladder
Descending
limb
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Ascending
limb
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

the value of a
counter current
exchange system
AP Biology
Recap…
AP Biology
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


AP Biology
urea
excess H2O
 excess solutes (glucose, salts)
toxins, drugs, “unknowns”
Maintaining Homeostasis
AP Biology
2009-2010
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
Endocrine System Control
Water Balance: Blood Osmolarity
ADH
pituitary
increased
water
reabsorption
high
blood osmolarity
blood pressure/volume
low
AP Biology
increase
thirst
nephron
ADH =
AntiDiuretic Hormone
Maintaining Water Balance
 High blood osmolarity level

too many solutes in blood
Get more
water into
blood
 dehydration, high salt diet

triggers release antidiuretic hormone (ADH)
 produced in hypothalamus
 stored in pituitary

makes collecting duct more permeability
to water
H2O
 increase water absorption back into blood
 more concentrated urine; decrease urination
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Alcohol
suppresses ADH…
makes you
urinate a lot!
H2O
H2O
Endocrine System Control
Blood Pressure / Volume
Oooooh,
zymogen!
high
blood osmolarity
blood pressure/volume
low
adrenal
gland
increased
water & salt
reabsorption
JGA =
JuxtaGlomerular
Apparatus
JGA
nephron
renin
aldosterone
AP Biology
angiotensinogen
angiotensin
Maintaining Water Balance
 Low blood volume or
low blood pressure

Get more
water & salt into
blood fast!
JGA releases renin which acts as an enzyme
 activates angiotensinogen  angiotensin

angiotensin acts as a hormone
 causes arterioles to constrict = raises blood pressure
 triggers release of aldosterone from adrenal gland

aldosterone acts as a hormone
 increases kidney reabsorption of Na+ & H2O
 puts more water & salts back in blood
Why such a
rapid response system?
AP Biology
Spring a leak?
adrenal
gland
Endocrine System Control
Water Balance
ADH
pituitary
increased
water
reabsorption
increase
thirst
nephron
high
blood osmolarity
blood pressure/volume
low
adrenal
gland
increased
water & salt
reabsorption
JuxtaGlomerular
Apparatus
nephron
renin
aldosterone
AP Biology
angiotensinogen
angiotensin
Don’t get batty…
Ask Questions!!
AP Biology
2009-2010