Biology - Homeostasis presentation
Transcript of Biology - Homeostasis presentation
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Homeostasis
Chapter 30
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Homeostasis
Homeostasis refers to maintaining
internal stability within an organism and
returning to a particular stable state after
a fluctuation.
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Homeostasis
Changes to the internal environment
come from:
Metabolic activities require a supply of
materials (oxygen, nutrients, salts, etc) that
must be replenished.
Waste products are produced that must be
expelled.
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Homeostasis
Systems within an organism function in
an integrated way to maintain a constant
internal environment around a setpoint.
Small deviations in pH, temperature,
osmotic pressure, glucose levels, & oxygen
levels activate physiological mechanisms to
return that variable to its setpoint. Negative feedback
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Osmoregulation & Excretion
Osmoregulation regulates solute
concentrations and balances the gain
and loss of water.
Excretion gets rid of metabolic wastes.
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Osmosis
Cells require a balance between osmotic
gain and loss of water.
Water uptake and loss are balanced by
various mechanisms of osmoregulation
in different environments.
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Osmosis
Osmosis is the movement of water
across a selectively permeable
membrane.
If two solutions that are separated by a
membrane differ in their osmolarity, water
will cross the membrane to bring the
osmolarity into balance (equal soluteconcentrations on both sides).
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Osmotic Challenges
Osmoconformers, which are only
marine animals, are isoosmotic with
their surroundings and do not regulate
their osmolarity.
Osmoregulators expend energy to
control water uptake and loss in a
hyperosmotic orhypoosmoticenvironment.
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Osmotic Regulation
Most marine invertebrates are osmotic
conformers their bodies have the
same salt concentration as the seawater.
The sea is highly stable, so most marine
invertebrates are not exposed to osmotic
fluctuations.
These organisms are restricted to a narrowrange of salinitystenohaline.
Marine spider crab
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Osmotic Regulation
Conditions along thecoasts and in estuariesare often more variablethan the open ocean.
Animals must be able tohandle large, often abruptchanges in salinity.
Euryhaline animals cansurvive a wide range ofsalinity changes by using
osmotic regulation. Hyperosmotic regulator
(body fluids saltier thanwater)
Shore crab.
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Osmotic Regulation
The problem of dilution is solved by
pumping out the excess water as dilute
urine.
The problem of salt loss is compensated
for by salt secreting cells in the gills the
actively remove ions from the water and
move them into the blood. Requires energy.
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Osmotic Regulation - Freshwater
Freshwater animals face an even more
extreme osmotic difference than those
that inhabit estuaries.
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Osmotic Regulation - Freshwater
Freshwater fishes have skin covered with scales andmucous to keep excess water out.
Water that enters the body is pumped out by thekidney as very dilute urine.
Salt absorbing cells in the gills transport salt ions intothe blood.
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Osmotic Regulation - Freshwater
Invertebrates and
amphibians also
solve these
problems in a similarway.
Amphibians actively
absorb salt from the
water through theirskin.
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Osmotic Regulation Marine
Marine bony fishes are hypoosmotic regulators.
Maintain salt concentration at 1/3 that of seawater.
Marine fishes drink seawater to replace water lost by
diffusion.
Excess salt is carried to the gills where salt-secreting cells
transport it out to the sea.
More ions voided in feces or urine.
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Osmotic Regulation Marine
Sharks and rays retain urea (a metabolic
waste usually excreted in the urine) in
their tissues and blood.
This makes osmolarity of the sharks
blood equal to that of seawater, so water
balance is not a problem.
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Osmotic Regulation Terrestrial
Terrestrial animalslose water byevaporation fromrespiratory and bodysurfaces, excretion(urine), andelimination (feces).
Water is replaced bydrinking water, waterin food, and retainingmetabolic water.
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Osmotic Regulation Terrestrial
The end-product of protein metabolism is
ammonia, which is highly toxic.
Fishes can excrete ammonia directly
because there is plenty of water to wash itaway.
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Osmotic Regulation Terrestrial
Terrestrial animals must convert
ammonia to uric acid.
Semi-solid urine little water loss.
In birds & reptiles, the wastes of developing
embryos are stored as harmless solid
crystals.
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Osmotic Regulation Terrestrial
Marine birds and
turtles have a salt
gland capable of
excreting highlyconcentrated salt
solution.
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Excretory Processes
Most excretory
systems produce
urine by refining a
filtrate derived frombody fluids (blood,
hemolymph, or
coelomic fluid).
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Excretory Processes
Key functions of most excretory systems
are:
Filtration, pressure-filtering of body fluids
producing a filtrate.
Reabsorption, reclaiming valuable solutes
from the filtrate.
Secretion, addition of toxins and othersolutes from the body fluids to the filtrate.
Excretion, the filtrate leaves the system.
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Invertebrate Excretory Structures
Contractile vacuoles are found in
protozoans and freshwater sponges.
An organ of water balance expels excess
water gained by osmosis.
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Invertebrate Excretory Structures
The most common type ofinvertebrate excretory organis the nephridium. The simplest arrangement
is the protonephridium of
acoelomates and somepseudocoelomates.
Fluid enters through flamecells, moves through thetubules, water andmetabolites are recoveredand wastes are excretedthrough pores that openalong the body surface. Highly branched due to
lack of circulatory system.
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Invertebrate Excretory Structures
The metanephridium isan open system found inannelids, molluscs, andsome smaller phyla.
Tubules are open atboth ends.
Water enters throughthe ciliated, funnelshaped nephrostome.
The metanephridium issurrounded by bloodvessels that assist inreclaiming water andvaluable solutes.
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Invertebrate Excretory Structures
In arthropods,antennal glands arean advanced form ofthe nephridial organ. No open
nephrostomes,hydrostatic pressureof the blood formsan ultrafiltrate in theend sac.
In the tubule,selective resorptionof some salts andactive secretion ofothers occurs.
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Invertebrate Excretory Structures
Insects and spiders haveMalpighian tubules thatare closed and lack anarterial supply.
Salts (especially
potassium) are secretedinto the tubules from thehemolymph (blood). Water & other solutes
(including uric acid)
follow. Water & potassium are
reabsorbed.
Uric acid is expelled infeces.
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Vertebrate Kidneys
Kidneys, the excretory organs of
vertebrates, function in both excretion
and osmoregulation.
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Vertebrate Kidneys
Nephrons and associated blood vessels
are the functional unit of the mammalian
kidney.
The mammalian excretory system
centers on paired kidneys which are also
the principal site of water balance and
salt regulation.
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Vertebrate Kidneys
Each kidney is
supplied with
blood by a renal
artery anddrained by a
renal vein.
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Vertebrate Kidneys
Urine exits each kidney through a duct
called the ureter.
Both ureters drain into a common urinary
bladder.
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Structure and Function of the Nephron
and Associated Structures
The mammalian kidney has two distinct
regions:
An outerrenal cortex
An innerrenal medulla
(b) Kidney structure
Ureter
Section of kidney from a rat
Renal
medulla
Renal
cortex
Renal
pelvis
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Structure and Function of the Nephron
and Associated Structures
The nephron, the
functional unit of
the vertebrate
kidney consists ofa single long
tubule and a ball
of capillaries
called theglomerulus.
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Filtration of the Blood
Filtration occurs as
blood pressure
forces fluid from the
blood in theglomerulus into the
lumen ofBowmans
capsule.
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Pathway of the Filtrate
From Bowmans
capsule, the filtrate
passes through three
regions of the nephron:
Proximal tubule
Loop of Henle
Distal tubule
Fluid from severalnephrons flows into a
collecting duct.
F Bl d Filt t t U i A
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From Blood Filtrate to Urine: A
Closer Look
Filtrate becomes urine as it flows through
the mammalian nephron and collecting
duct.
The composition of the filtrate is modified
through tubular reabsorption and secretion.
Changes in the total osmotic concentration
of urine through regulation of waterexcretion.
F Bl d Filt t t U i A
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From Blood Filtrate to Urine: A
Closer Look
Secretion and reabsorption in the proximal
tubule substantially alter the volume and
composition of filtrate.
Reabsorption of water continues as the filtratemoves into the descending limb of the loop of
Henle.
F Bl d Filt t t U i A
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From Blood Filtrate to Urine: A
Closer Look
As filtrate travels through the ascendinglimb of theloop of Henle salt diffuses outof the permeable tubule into the interstitial
fluid. The distal tubule plays a key role in
regulating the K+ and NaCl concentration ofbody fluids.
The collecting duct carries the filtratethrough the medulla to the renal pelvis andreabsorbs NaCl.
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Conserving Water
The mammalian kidneys ability to
conserve water is a key terrestrial
adaptation.
The mammalian kidney can produce
urine much more concentrated than body
fluids, thus conserving water.
Solute Gradients and Water
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Solute Gradients and Water
Conservation
In a mammalian kidney, the cooperative
action and precise arrangement of the
loops of Henle and the collecting ducts
are largely responsible for the osmoticgradient that concentrates the urine.
Solute Gradients and Water
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Solute Gradients and Water
Conservation
The collecting duct, permeable to water
but not salt conducts the filtrate through
the kidneys osmolarity gradient, and
more water exits the filtrate by osmosis.
Solute Gradients and Water
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Solute Gradients and Water
Conservation
Urea diffuses out of the collecting duct
as it traverses the inner medulla.
Urea and NaCl form the osmotic gradient
that enables the kidney to produce urine
that is hyperosmotic to the blood.
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Regulation of Kidney Function
The osmolarity of the urine is regulated
by nervous and hormonal control of
water and salt reabsorption in the
kidneys.
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Regulation of Kidney Function
Antidiuretic
hormone (ADH)
increases water
reabsorption in thedistal tubules and
collecting ducts of
the kidney.
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Temperature Regulation
Animals must keep their bodies within a
range of temperatures that allows for
normal cell function.
Each enzyme has an optimum
temperature.
Too low and metabolism slows.
Too high and metabolic reactions becomeunbalanced. Enzymes may be destroyed.
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Temperature Regulation
Poikilothermicanimals body
temperatures fluctuate with
environmental temperatures.
Homeothermicanimals body
temperatures are constant.
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Temperature Regulation
All animals produce heat from cellularmetabolism, but in most this heat is lostquickly.
Ectotherms lose metabolic heat quickly,so body temperature is determined by theenvironment. Body temp may be regulated environmentally.
Endotherms retain metabolic heat andcan maintain a constant internal bodytemperature.
Ectothermic Temperature
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Ectothermic Temperature
Regulation
Many ectotherms regulate body temperature
behaviorally.
Basking to increase temperature.
Shelter in shade or coolness of a burrow todecrease temperature.
Ectothermic Temperature
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Ectothermic Temperature
Regulation
Most ectotherms can also adjust their
metabolic rates to the environmental
temperature.
Activity levels can remain unchanged over awider range of temperatures.
Endothermic Temperature
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Endothermic Temperature
Regulation
Constant temperature in endotherms is
maintained by a delicate balance
between heat production and heat loss.
Heat is produced by the animalsmetabolism.
Producing heat requires energy supplied
by food. Endotherms must eat more in cold weather.
Endothermic Temperature
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Endothermic Temperature
Regulation
If an animal is toocool, it cangenerate heat byincreasingmuscular activity
(exercise orshivering). Heat isretained throughinsulation.
If an animal is too
warm it decreasesheat productionand increases heatloss.
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Adaptations for Hot Environments
Small desert mammals are mostly
fossorial (living underground) or
nocturnal.
Burrows are cool and moist.
Adaptations to derive water from
metabolism and produce concentrated
urine & dry feces.
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Adaptations for Hot Environments
Larger desert mammals(camels, desertantelopes) have differentadaptations. Glossy, pallid color
reflects sunlight. Fat tissue is
concentrated in ahump, rather thanbeing evenly distributedin an insulating layer.
Sweating and pantingare ways of dumpingheat.
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Adaptations for Cold Environments
In cold environments,mammals reduce heatloss by having a thickinsulating layer of fat,fur, or both.
Heat production isincreased.
Extremities are allowedto cool.
Heat loss is preventedthroughcountercurrent heatexchange.
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Adaptations for Cold Environments
Small mammals are not as well
insulated.
Many avoid direct exposure to the cold by
living in tunnels under the snow. Subnivean environment.
This is where food is located.
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Adaptive Hypothermia
Endothermy is energetically expensive.
Ectotherms can survive weeks without
eating.
Endotherms must always have energysupplies.
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Adaptive Hypothermia
Some very small
mammals & birds
(bats or
hummingbirds)maintain high body
temperatures when
active, but allow
temperatures to dropwhen sleeping.
Daily torpor
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Adaptive Hypothermia
Hibernation is a way to solve
the problem of low
temperatures and the scarcity
of food.
True hibernators store fat,then enter hibernation
gradually.
Metabolism & body slows to a
fraction of normal.
Body temperature decreases.
Shivering helps increase
temperatures when they are
waking up.
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Adaptive Hypothermia
Other mammals, such as bears,
badgers, raccoons and opossums enter
a state of prolonged sleep, but body
temperature does not decrease.
Ad i H h i
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Adaptive Hypothermia
Adverse conditions can also occur during
the summer.
Drought, high temperatures.
Some animals enter a state of dormancy
called estivation.
Breathing rates and metabolism decrease.
African lungfish, desert tortoise, pigmymouse, ground squirrels.