Transcript Control of the Internal Environment

CONTROL OF THE INTERNAL
ENVIRONMENT
Chapter 25
THERMOREGULATION

Maintenance of an
internal temperature

Life processes are
temperature sensitive
Stable internal
temperature despite
external fluctuations
 Endotherms use their
metabolism


Some reptiles, fish, and
insects too
Ectotherms gain heat
from external sources
 Not mutually exclusive

HEAT EXCHANGE

Conduction: molecules
between 2 objects in
direct contact
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Higher to lower
temperature movement
Convection: movement
of air or liquid past an
object
Radiation:
electromagnetic waves
between 2 objects not in
direct contact
Evaporation: surface
of a liquid losing
molecules as a gas
ADAPTATIONS FOR THERMOREGULATION

Metabolic heat


Hormonal boost or moving around to contract skeletal muscles, i.e
shivering
Insulation
Hair, fur and feathers rise to trap insulating layer of air, goose
bumps are vestigial remnant
 Blubber in aquatic birds and mammals


Circulatory adaptations
Change blood flow by constricting blood vessels to surfaces to
conserve heat, dilation to dissipate
 Countercurrent heat exchange: adjacent vessels flow opposite
directions
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Evaporative cooling
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Standing on ice, cold water across gills, and muscles
Sweating and panting expose moisture to be removed with heat
Behavioral response

Migration, basking in sun when cold and damp areas when hot,
bathing, and layered clothing
OSMOREGULATION

Balancing uptake and loss of water and solutes

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Osmoconformers: no net gain or loss of water
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Animal cells: net uptake = ? Net loss = ?
Water follows solutes by osmosis
Marine invertebrates have body fluids of similar [solute] as
seawater
Osmoregulators: necessary to regulate to prevent
changes

Freshwater fish have higher [solute] than environment

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Saltwater fish have lower [solute] than environment
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H2O gained and salt lost = doesn’t drink H20, ions from food, and
lots of dilute urine
H2O lost and salt gained = drinks salt H2O with salt out gills and
little concentrated urine
Land animals obtain H2O from food and drink while losing
water through evaporation and excretion

Exoskeleton, dead skin layers, egg shells, and amnitotic sac to
prevent dehydration
DISPOSAL OF WASTES

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Metabolism produces toxic
nitrogenous wastes that
are removed by excretion
Form of waste depends on
habitat and evolution
Ammonia too toxic to
store, but diffuses in water
Urea less toxic so can be
stored, but costs energy
and H2O loss to remove
Uric acid insoluble in
H2O so is semisolid

Costs more energy, but
conserves H2O
URINARY SYSTEM

Forms and excretes urine
while regulating water
and ion concentrations in
body fluids
Kidneys filter blood to
extract filtrate which
contains H2O, urea,
glucose, AA’s, ions, and
vitamins
 Filtrate is processed so
valuable solutes not lost in
urine


Blood enters kidney
through the renal arteries
to be filtered and leaves
via the renal veins

What is the urine pathway
from kidneys to outside?
THE KIDNEYS

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Consist of renal cortex
(outer) and renal medulla
(inner)
Nephrons are the
functional units

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Bowman’s capsule
encloses the glomerulus
which filters the blood
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Start and end in cortex, part
in medulla
Nephron tubule has 3 parts
Drains to collecting duct to
join filtrate from other
nephrons
Capillary system in
Bowman’s capsule and
around tubule system
URINARY SYSTEM PROCESSING
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Filtration
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Reabsorption
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Filtrate returns valuable solutes to blood (tubule capillaries)
Secretion
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H2O and small molecules through capillary tube from glomerulus
to nephron tubule
Excess ions, drugs, and toxic substances from blood transported
into filtrate (tubule capillaries)
Excretion

Urine from kidneys to outside
BLOOD FILTRATE TO URINE
NaCl enters
interstitial fluid,
bringing H2O with
Excess H+ secreted
and HCO3reabsorbed to
maintain blood pH
Toxins from liver
into tubule system
Loop of Henle
facilitates H2O
reclaimation
ADH sets amount
of H2O
reabsorbtion
Lots of H2O dilutes
solutes so ADH
down = less H2O
retained
Alcohol inhibits
ADH release =
excess H2O loss