Transcript Nerve activates contraction

REGULATION - what does this word
mean to you?
• Why?
• What?
• How?
Set point =
homeostasis
CHAPTER 44
REGULATING THE INTERNAL
ENVIRONMENT
Regulation of Body Temperature
*Ectotherms -use outside heato warm upbody temperatures close to environmental
temperature;
*Endotherms can use metabolic heat to
keep body temperature warmer than their
surroundings
Fig. 44.4
• It is not constant body temperatures that
distinguish endotherms from ectotherms.
(WHAT??).
•They both can maintain constant body temp.
but it is HOW they go about it.
Aahh the sun!
Its always cool here!
• Thermoregulation= rate of heat gain exactly
matches the rate of heat loss.
Why thermoregulate?
• Q10 effect - The rates for most enzyme-mediated
reactions increase by a factor of 2-3 for every 10oC
temperature increase, until temperature is high
enough to denature proteins.
• Plasma membrane fluidity (structure) depends on
temperature – high temp membrane can “melt”
• Endothermy advantages:
• Live on land - more varible than water in temp.
• High levels of aerobic metabolism = more ATP, more cellular
work like movement, biosynthesis.
• Perform vigorous activity for much longer
• Live in extreme conditions - many ectotherms die in winter
• What is the price to be an aerobically fit
ENDOTHERM?
• Food consumed: Human -1,300 to 1,800 kcal per day at
200C
• American alligator- 60 kcal per day at 200C.
Thermoregulation in endotherms involves
physiological and behavioral adjustments
(1) Adjusting the rate of heat exchange between the animal and its
surroundings.
•
Insulation-fat
•
Vasodilation- blood vessels enlarge, heat is lost to the skin
•
Vasoconstriction-blood vesels onstrict, trapping heat in
• Countercurrent heat exchanger helps trap heat in
the body core and reduces heat loss.
• Artery and vein are arranged with opposing blood
flow. This allows for heat to exchange all along
the length of the blood vessel and maintain warm
core temp.
(2) Cooling by evaporative heat loss - sweat allows
body to cool off when water evaporates.
•(3) Behavioral responses - panting,
licking paws, sunning….
• (4) Changing the rate of metabolic heat
production-shivering
And then there is
the frozen frog!!!
Quic kTime™ and a
TIFF (Unc ompres sed) dec ompres sor
are needed t o s ee t his pict ure.
CHAPTER 44
REGULATING THE INTERNAL
ENVIRONMENT
Water Balance and Waste Disposal
•When two solutions differ in osmolarity (solute
• THIS IS REVIEW :
concentration), the one with the greater concentration of
• Osmolarity
of solute per liter
of solution)
solutes
is referred-(moles
to as hyperosmotic
and the
more dilute
(mosm/L).
solution
is hypoosmotic. (Blood - 300mosm/L, sea water1000mos/L, fresh water - 10 mosm/L)
•Water flows by osmosis from a hypoosmotic solution to
a hyperosmotic one.
•Isoosmotic solutions – no net movement
• Osmoregulation - Management of the body’s water content and solute
composition; maintenance of an osmolarity difference between the body and the
surrounding costs energy (ATP).
• Osmoregulators - different osmotic concentration than surrounding
• Osmoconformer - same osmolarity as surrounding
Osmoregulators expend energy (active
transport) to control their internal osmolarity
Osmoconformers are iso-osmotic with
their surroundings (Marine Invertebrates)
•Stenohaline- cannot tolerate substantial changes in
external osmolarity
•Euryhaline can survive large fluctuations in external
osmolarity (osmoconformers and salmon).
Salmon
Petrolisthes armatus
(CRAB)
Important!
Fig. 44.14a
Is this protist (Paramecium) an osmoregulator or
osmoconformer - it lives in fresh water
• Anhydrobiosis – loose most of the water (water
bears ex.tardigrades/water bears dehydrate to 2%
of their weight!!!)
Fig. 44.15
Fig. 44.13
Ammonia excretion
= more water
needed (toxic)
Urea excretion =
less toxic
Quic kTime™ and a
TIFF ( Unc ompres s ed) dec ompr ess or
are needed to s ee this pic ture.
Water balance and waste disposal depend
on transport epithelia
• Water birds can actually excrete sea water!! They
excrete the salt through salt excreting glands
• Freshwater fishes actively pump salts from the gills
• So what helps this
into their blood (review)
process? AND
HOW???
• Transport
epithelium - helps
both water and
Nitrogen waste
removal
Water balance and waste disposal depend
on transport epithelia
• Transport epithelium THIN layer of cells
that faces the outside
directly or through
tubes that open to the
outside. The
circulatory fluid is in
close contact with the
transport epithelium why? Tight junctions
between cells - why?
CHAPTER 44
Excretory Systems
How is URINE produced?
Excretory systems produce urine by refining a filtrate derived
from body fluids
• Three-step process.
• body fluid (blood, coelomic fluid, or
hemolymph) is filtered so solutes and water
move out from body fluid to the excretory
tubule (has transport epithelia).
• the composition of the collected fluid is
adjusted by selective reabsorption (important
solutes move backby ACTIVE TRANSORT
into blood).
• Toxins, and other solutes are secreted or
passed into the tubule for excretion. Water and
small solutes, such as salts, sugars, amino
acids, and nitrogenous wastes, collectively
called URINE moves into the excretory
tubule -
Diverse excretory systems are variations on
a tubular theme
• Flatworms have an excretory system
called protonephridia,
consisting of a branching
network of dead-end tubules.
• These are capped by a
flame bulb with a tuft
of cilia that draws water
and solutes from the
interstitial fluid, through
the flame bulb, and into
the tubule system.
Fig. 44.18
• Metanephridia, another tubular excretory system,
consist of internal openings that collect body fluids
from the coelom through a ciliated funnel, the
nephrostome, and release the fluid through the
nephridiopore.
• Found in most annelids, each segment of a worm has a
pair of metanephridia.
Fig. 44.19
• Insects and other terrestrial arthropods have organs
called Malpighian tubules that remove
nitrogenous wastes and also function in
osmoregulation.
• These open into the
digestive system
and dead-end at
tips that are
immersed in
the hemolymph.
Fig. 44.20
• The kidneys of vertebrates usually function in
both osmoregulation and excretion. We produce
hyperosmotic (to blood) urine
Renal Artery and
Renal Vein
Medulla - inner
part
• Kidney - an outer renal cortex
and an inner renal medulla.
• Structural unit of kidney =
NEPHRON
• Cortex has glomerulus part of
nephrons (a million) and blood
vessels.
• Medulla- has the collecting
tubules of the nephron
• Each nephron consists of a single
long tubule and a ball of
capillaries, called the glomerulus.
• The blind end of the tubule forms
a cup-shaped swelling, called
Bowman’s capsule
• Nephron tubules are lined by
transport epithelia
Bowman’s
Capsule –
blind end of
excretory
tubule
Glomerulus capillaries
NEPHRON
Fig. 44.21
Glomerulus
Bowman’s
capsule
Proximal
Tube
Distal Tube
Loop of
Henle
Collecting
Duct
C. Glomerulus
B. Bowman’s
capsule
G. Proximal
Tube
D. Distal Tube
F. Loop of
Henle
E. Collecting
Duct
Glomerulus
Bowman’s
capsule
Proximal
Tube
Distal Tube
Loop of
Henle
Collecting
Duct
Filtration occurs as blood pressure
forces fluid from the blood in the
glomerulus into the lumen of
Bowman’s capsule.
The porous capillaries, are
permeable to water and small
solutes but not to blood cells or
large molecules such as plasma
proteins.
The filtrate in Bowman’s capsule
contains salt, glucose, vitamins,
nitrogenous wastes, and other
small molecules.
Cortex
Medulla
• Filtrate from Bowman’s capsule flows through the
nephron and collecting ducts as it becomes urine.
Fig. 44.22
The mammalian kidney’s ability to
conserve water is a key terrestrial
adaptation
• The osmolarity of human blood is about 300
mosm/L, but the kidney can excrete urine up to four
times as concentrated - about 1,200 mosm/L.
• Nephrons can be thought as tiny energy-consuming
machines whose function is to produce a region of high
osmolarity in the kidney, which can then extract water
from the urine in the collecting duct.
• The two primary solutes used to produce the high
osmolarity are - NaCl and urea.
• The ability of the mammalian kidney to convert
interstitial fluid at 300 mosm/L to 1,200 mosm/L as
urine depends on a counter- current multiplier between
the ascending and descending limbs of the loop of
Henle.
Fig. 44.23
•Regulation of blood osmolarity is maintained by
hormonal control of the kidney by negative feedback
circuits.
Fig. 44.24a
Antidiuretic hormone (ADH)
Juxtaglomerular apparatus- located near the arteriole that supplies the
glomerulus. When BP and Blood volume drop in the JGA, enzyme renin
secreted -> converts angiotensinogen into angiotensin. Angiotensin ->
constricts blood vessels -> less blood flow into kidneys; stimulates salt
and water reabsorption; causes Aldosterone to be released by adrenal
glands (same effect on kidneys) - RAAS - renin-angiotensin-aldosterone
system
Fig. 44.24b
• Why have 2 systems - ADH and RAAS for 1
purpose?
• Normally, ADH and the RAAS are partners in
homeostasis.
• ADH alone stimulates only water reabsorption in the
kidney.
• But the RAAS helps maintain balance by stimulating
salt and water reabsorption.
• Compare blood loss in an accident to blood osmolarity
increase due to a high salt diet
• The South American vampire bat, Desmodus
rotundas- feeds on the blood of large birds and
mammals by making an incision in the victim’s
skin and the lapping up blood from the victim
• Excretes huge amounts of dilute urine so it can be
light enough to FLY
Fig. 44.25
5. Diverse adaptations of the vertebrate
kidney have evolved in different habitats
• Variations in nephron structure and function equip
the kidneys of different vertebrates for
osmoregulation in their various habitats.
• Mammals that excrete the most hyperosmotic urine, such
as hopping mice and other desert mammals, have
exceptionally long loops of Henle.
• This maintains steep osmotic gradients, resulting in
urine becoming very concentrated.
• In contrast, beavers, which rarely face problems of
dehydration, have nephrons with short loops, resulting in
much lower ability to concentrate urine.
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• Birds, like mammals, have kidneys with
juxtamedullary nephrons that specialize in
conserving water.
• However, the nephrons of birds have much shorter
loops of Henle than do mammalian nephrons.
• Bird kidneys cannot concentrate urine to the
osmolarities achieved by mammalian kidneys.
• The main water conservation adaptation of birds is use
of uric acid as the nitrogen excretion molecule.
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• The kidneys of reptiles, having only cortical
nephrons, produce urine that is, at most,
isoosmotic to body fluids.
• However, the epithelium of the cloaca helps conserve
fluid by reabsorbing some of the water present in urine
and feces.
• Also, like birds, most terrestrial reptiles excrete
nitrogenous wastes as uric acid.
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• In contrast to mammals and birds, a freshwater fish
must excrete excess water because the animal is
hyperosmotic to its surroundings.
• Instead of conserving water, the nephrons produce a
large volume of very dilute urine.
• Freshwater fishes conserve salts by reabsorption of ions
from the filtrate in the nephrons.
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• Amphibian kidneys function much like those of
freshwater fishes.
• When in fresh water, the skin of the frog accumulates
certain salts from the water by active transport, and the
kidneys excrete dilute urine.
• On land, where dehydration is the most pressing
problem, frogs conserve body fluid by reabsorbing
water across the epithelium of the urinary bladder.
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• Marine bony fishes, being hypoosmotic to their
surroundings, have the opposite problem of their
freshwater relatives.
• In many species, nephrons lack glomeruli and
Bowman’s capsules, and concentrated urine is produced
by secreting ions into excretory tubules.
• The kidneys of marine fishes excrete very little urine
and function mainly to get rid of divalent ions such as
Ca2+, Mg2+,and SO42-, which the fish takes in by its
incessant drinking of seawater.
• Its gills excrete mainly monovalent ions such as Na+
and Cl- and the bulk of its nitrogenous wastes in the
form of NH4+.
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6. Interacting regulatory systems maintain
homeostasis
• Numerous regulatory systems are involved in
maintaining homeostasis in an animal’s internal
environment.
• The mechanisms that rid the body of nitrogenous wastes
operate hand in hand with those involved in
osmoregulation and are often closely linked with energy
budgets and temperature regulation.
• Similarly, the regulation of body temperature directly
affects metabolic rate and exercise capacity and is closely
associated with mechanisms controlling blood pressure,
gas exchange, and energy balance.
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• Under some conditions, usually at the physical
extremes compatible with life, the demands of one
system may come into conflict with those of other
systems.
• For example, in hot, dry environments, water
conservation often takes precedence over evaporative
heat loss.
• However, if body temperature exceeds a critical upper
limit, the animal will start vigorous evaporative cooling
and risk dangerous dehydration.
• Normally, however, the various regulatory systems act
together to maintain homeostasis in the internal
environment.
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• The liver, the vertebrate body’s most functionally
diverse organ, is pivotal to homeostasis.
• For example, liver cells interact with the circulatory
system in taking up glucose from the blood.
• The liver stores excess glucose as glycogen and, in
response to the body’s demand for fuel, converts
glycogen back to glucose, releasing glucose to the
blood.
• The liver also synthesizes plasma proteins important in
blood clotting and in maintaining osmotic balance in the
blood.
• Liver cells detoxify many chemical poisons and prepare
metabolic wastes for disposal.
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