Regulating The Internal Environment

1
Regulating The Internal Environment
2
Homeostasis

• The ability of animals to regulate their internal
  environment.
• Thermoregulation - the ability of animals to
  regulate their internal temperature.
• Osmoregulation the ability of animals to
• regulate their water balance.
• Excretion how animal s rid themselves of
  nitrogenous wastes.

3
An Overview of Homeostasis

• Regulators - actively regulate their own
  internal environment in response to external.
• Cannot tolerate large internal changes.
• Salmon are osmoregulators
• Endotherms are thermoregulators
• Conformers allow some conditions to vary in
  response to the external environment.
• Live in relatively stable environments and
  somewhat conform to their external environment.
• Spider crabs will gain or lose water in reponse
  to a variation in salinity.

4
Regulaters Verses Conformers
5
No Organism is a Perfect Conformer or Regulator

• Salmon may osmoregulate but they generally
  conform to the external temperatures.
• For a particular condition animals may regulate
  or conform.
• A forest dwelling lizard may have to travel long
  distances to perch in the sun and therefore
  choose to regulate its body temperature in the
  forest to avoid predation. The same lizard may
  choose to bask in the sun in open predation.

6
Biochemical and Physiological Processes Vary With
Body Temperature.

• Enzyme mediated reactions may vary 2-3 fold for
  every 10o C temperature increase.
• Q10 effect multiple by which a particular
  process increases with a 10o increase in body
  temperature.
• Glycogen hydrolysis occurs 2.5 greater at 30oC
  than 20oC then the Q10 of the reaction is 2.5.
• Membranes are affected by temperature and can
  affect animal unction.
• Muscle contractions can be affected and the
  ability of the animal to run, jump or fly.
• All animals have an optimal temperature in which
  they can function.

7
Physical Processes Account for Heat Lost or
Gained.

• Conduction - Direct transfer of heat through
  contact with the environment.
• Convection - transfer of heat by the movement of
  a liquid or gas past a surface.
• Radiation - emission of electromagnetic radiation
  from objects.
• Evaporation heat removal through evaporation

8
Heat Exchange
9
Cool Purple Lizard on a Rock
10
Ectothermy Verses Endothermy

• Ectotherms generate such little heat through
  metabolism that their body temperature is
  determined by the environment.
• Because endotherms can maintain a stable internal
  temperature they can sustain prolonged
  activities.
• Endotherms are also better designed to live on
  land and can tolerate the large fluxuations in
  temperature.
• A disadvantage of being an endotherm is that they
  must consume much more food because of their
  energy needs.

11
Endotherms Verses Ectotherms
12
Physiological Thermoregulation

• Adjusting the rate of heat exchange between the
  organism and its environment.
• Insulation fur and feather fluffing
• Vasodilation dilate blood vessels at the
  surface of the skin to dissapate heat.
• Vasoconstriction constrict blood vessels to
  direct blood towards the core and away from the
  extremities where heat is lost.

13
Countercurrent Heat Exchange

• Arrangement of blood vessels are designed to
  either trap or release heat more efficiently.
• Arteries carrying warm blood from the animals
  core are in close proximity to the cooler blood
  in the veins returning to the core.
• Keeps artic wolf legs from freezing.
• By counter current exchange un-insulated toe pads
  are kept just above 0 o C to prevent heat loss
  but not cold enough to freeze.
• Help dissipate heat when running long distances.

14
Counter Current Heat Exchange
15
Puffin
16
(No Transcript)
17
Warm Blood Heats Cold Blood
18
Great White Shark
19
Thermoregulation of the Shark
20
(No Transcript)
21
Skin Section
22

• Evaporative Cooling
• Sweating
• Panting
• Making their bodies wet
• Behavioral
• Change posture
• Migrate
• Bask in the sun or go swimming
• Changing the rate of metabolic heat production
• Non-shivering thermogenesis
• Brown fat lipid found in the neck and shoulders
  of some animals that create mostly thermal energy

23
Happy Happy Hippos
24
Invertebrates

• Mostly thermoconformers
• Desert locusts dont move until they warm up.
• Some bees and moths are endothermic
• Flight muscles generate heat
• Some shiver to produce heat
• Countercurrent exchange
• Some bees huddle together when cold
• Some bees transport water to the hive and
  evaporate the water by fanning their wings.

25
Adjustment to Changing Temperatures

• Nerves in the skin sense temperature changes and
  the hypothalamus in the brain responds.
• Acclimmatization is a physiological response to
  temperature change over a period of weeks or
  days.
• Grow a thicker coat or shed.
• Produce enzymes that work at different
  temperatures.
• Membranes change proportion of saturated verses
  unsaturated fatty acids within the phospholipds.
• May creates cryoprotectant compounds.

26

• Cells can make rapid adjustments in response to
  extreme stress.
• Heat shock proteins help maintain the integrity
  of other proteins that would denature under
  extreme heat.
• The physiological adaptations that animals make
  during acclimatization affect their tolerance to
  temperature.
• Summer acclimatization of the bull heaeded cat
  fish can survive water temperatures of 36oC but
  cannot function in cold water.

27
(No Transcript)
28
How Animals Deal With Environmental Extremes

• Torpor is a physiological state in which activity
  is low and metabolism decreases.
• Hibernation is a long term winter torpor.
• Estivation is a long term summer torpor when
  sources of water are scarce.
• Daily Torpor is a short term torper
• Adpated to feeding patterns.
• Shrews feed at night and are inactive during the
  day.
• Appears to be controlled by a biological clock.

29
The Beldings squirrel can live on one Kcal per
day while hibernating
30
Water and Waste Disposal
31
Osmoregulation

• Management of the bodys solute concentration.
• Management of water into and out of the body.
• Depends on transport epitheilium.
• Layer or layers of specialized cells that
  regulate solute movements in a particular
  direction and in certain quantities.

32
Structure Verses Function

• Some of these epitheilia
• Face outwards
• Line openings
• Are arranged in tubular networks that have large
  surface areas.
• Joined by tight junctions to create barriers
  between the environment and body tissue

33
Salt Excreting glands in Birds
34
The Nature of Nitrogenous Waste

• Nitrogenous wastes are created through
  de-amination, the removal of an amine group from
  of proteins and nucleic acids.
• Primary toxic product is ammonia.
• These wastes must be dissolved in water and
  therefore affect the water balance.

35
Nitrogenous Waste Depends on Habitat

• The kinds of nitrogenous waste an animal excretes
  depends on the availability of water in its
  habitat and evolutionary history.
• The amount and composition of waste produced
  depends on energy needs and diet.
• Endotherms have high energy needs and
  consequently excrete more than ectotherms.
• Carnivores take in large amounts of protein and
  excrete large amounts of nitorgenous watse.

36
(No Transcript)
37
Ammonia

• Animals that live in the water can excrete
  ammonia.
• They can simply swim away from their waste.
• Requires less energy to convert ammonia to
  something else.
• In Fish most of the ammonia is lost as ammonium
  ions(NH4) across the gills and the kidneys only
  excrete a small amount of waste

38
Urea

• Since terrestrial animals have to carry their
  waste around with them ammonia is much too toxic.
  
• Ammonia is converted to urea by combining CO2 and
  ammonia.
• It takes energy to do this and is consequently
  reflected in their energy
• budget.
• Mammals, adult amphibians and many marine fishes
  excrete urea.
• Urea can be excreted in much more concentrated
  solutions because it is less toxic than ammonia.
• Many amphibians excrete ammonia as tadpoles but
  switch to urea as adults.

39
Uric Acid

• Land snails, insects, reptiles and birds excrete
  uric acid.
• Egg layers and flying organisms that cannot carry
  a lot of water excrete solid waste only.
• Uric acid is the least toxic and precipitates.
• Settles to the bottom of the egg to protect
  growing bird or reptile embryo.
• Keeps insects from drying out and makes them
  light for flight.
• Tortoises can switch from urea to uric acid when
  there is a deficit of water in the environment.

40
(No Transcript)
41
Osmoconformers Verses Osmoregulators

• There are two solutions to maintaining internal
  water balance.
• Osmoconformers match the osmolarity of the
  environment.
• Osmoregulators actively absorb or excrete solutes
  to maintain a constant internal osmolarity within
  body tissues.
• The osmolarity of blood is approximately 300
  millimoles per liter(mosm/L).
• Sea water is approximately 1000 mosm/L

42
Extreme Environments

• Being an osmoregulator is expensive.
• Most animals are stenohaline.
• Steno means narrow , haline means salt.
• Euryhaline animals can tolerate large osmotic
  fluxuations in their external environment.
• Eurys means broad(Greek)

43
Maintaining Water Balance in the Sea

• Invertebrates are osmoconformers.
• Even though the osmolarity of their tissues match
  the environment they do regulate the composition
  of their internal environment. (specific solutes)
• Marine vertebrates except hagfish are
  osmoregulators.
• These animals constantly lose water to the
  environment.
• Must drink large amounts of water and excrete
  excess salts through their gills.
• Sharks are actually hyperosmotic to their
  environment because they concentrate urea in
  their tissues. They protect themselvs from the
  toxicity of urea with TMAO (trimethylamine
  oxide).
• Water enters the sharks body by diffusion so
  they dont drink.

44
Maintaining Osmotic Balance In Fresh Water

• Fresh water organisms are constantly gaining
  water because their tissues are hyperosmotic to
  their environment.
• Fresh water protists (Amoeba and Paramecium) have
  contractile vacuoles pump the excess water out.
• Most fresh water organisms excrete dilute urine
  and replenish salt through their diet.
• Salmon osmoregulate while in the ocean by
  drinking water and excreting slat through their
  gills and cease drinking and excrete dilute urine
  while in fresh water.

45
(No Transcript)
46
(No Transcript)
47
Special Problems

• Anhydrobiosis
• Organism completely dehydrates and enters a
  dormant state until water is available again.
• Membrane remains in tact during dehydration
  because trehalose (disaccharide) replaces water.
• Desert Kangaroo rat lives entirely on water
  created by their metabolism.

48
Kangaroo Rat from the South West
49
Osmotic Balance on Land

• Skin and keratinized shells prevent animals and
  insects from drying out.
• Waxy cuticles for plants.
• Drink water and eat moist food.
• Produce metabolic water (mitochondria)
• Go out at night time.

50
Anhydrobiosis of the Tardigrade
51
EXCRETORY SYSTEMS
52
OVERVIEW

• Body fluid is collected and filtered
• Hemolymph, blood, coelomic fluid
• Usually filtered by selectively permeable
  membranes of transport epithelia.
• Large proteins and cells are left behind.
• Hydrostatic pressure forces water and small
  solutes through.
• Salts
• Sugars
• Amino acids
• Nitrogenous wastes
• Largely non selective filtering occurs here.

53

• Selective absorption or secretion
• Now called the filtrate, its composition
  adjusted.
• Active transport is used to selectively reabsorb
  essential nutrients.
• Glucose
• Some salts
• Amino acids
• Wastes are left in the filtrate to be excreted.

54
(No Transcript)
55
Protonephridia of the Flatworm
56
Metanephridia of the Annelid
57
Malpighian Tubules of the Insect
58
(No Transcript)
59
(No Transcript)
60
(No Transcript)
61
(No Transcript)
62
Counter Current Exchange
63
(No Transcript)
64
(No Transcript)
65
Antidiuretic Hormone

• When there is an increase in osmolarity in the
  blood
• Osmoreceptors present in the hypothalamus make us
  feel thirsty.
• Antidiuretic Hormone is released by the
  pituitary gland and causes water to be reabsorbed
  in the collecting duct by increasing its
  permeability.

66
Rennin Angiotensin Aldosterone System

• RAAS is another mechansim that maintains the
  osmolarity of the blood.
• The jusxtaglomerular apparatus is a patch of
  tissue that within the afferent blood vessel that
  feeds blood to the glomurulus that responds tto a
  drop in blood pressure.
• In response to this drop in blood pressure the
  JGA releases renin which turns angiotensin into
  angiotensin II.
• Angiotensisn II constricts blood vesseles to
  increase blood pressure.

67
Aldosterone and the Adrenal Glands

• Angiotensis II also stimulates the adenal glands
  located on top of the kidneys to release
  Aldosterone.
• Aldosternone causes Na to be reabsorbed in the
  distal tubule and water follows.
• Ensures that the blood does not become diluted
  in response to the reabsorption of water.
• A hormone called atrial natriuretic factor is
  released from the atrium responds to an increase
  of blood pressure and is the off switch for RAAS.

68
How the Gradient is Maintained

• The juxtamedullary nephron uses the gradient in
  the kidney to excrete urine that is hyperosmotic
  to the kidney tissue.
• The descending Loop of Henle is permeable to H2O
  but not NaCl.
• As filtrtate moves towards the medulla H2O
  diffuses out.
• The filtrate becomes increasing hyperosmotic.
• The filtrate has the highest osmolarity at the
  bottom of the loop.

69

• The ascending Loop of Henle is permeable to salt
  but not water.
• Since the filtrate at this point is hyperosmotic
  to the kidney NaCl diffuses out.
• This contributes to the high osmolarity of the
  medulla.
• At the upper portion of the ascending loop salt
  moves out through active transport which requires
  ATP
• This ensures that the gradient will not dissapte.

70
Counter Current Exchange Also Maintains the
Gradient

• Capillaries that surround the nephron are called
  the vasa recta.
• The blood in the capillaries that surround the
  descending loop of Henle lose water and gain
  salt.
• The blood in the capillaries that surround the
  ascending loop of Henle lose salt and gain water.
• This helps maintain the gradient in the kidney.

71
How Terrestrial Animals Excrete Urine That is
Hyperosmotic

• When the filtrate reaches the distal tubule it is
  hypoosmotic because NaCl has been removed by
  active transport.
• When the filtrate descends back towards the
  medulla in the collecting duct H2O diffuses out
  because the collecting duct is permeable to H2O
  and not salt.
• This concentrates salt and urea in the filtrate.
• Urea leaks out at the bottom of the collecting
  duct which contributes the gradient.
• The filtrate is isoosmotic to the inner medulla
  when it empties into the renal pelvis but is
  hyperosmotic to the blood and interstitial fluid
  in the rest of the body.

72
Special Adaptations of the Kidney

• Vampire bats can switch from excreting large
  amounts of dilute urine while feeding to
  excreting urine concentrated with urea while
  roosting.

73
Diverse Adaptations of the Nephron

• Desert animals excrete hyperosmotic urine.
• Have exceptionally long loops of Henle to allow
  for maximum absorption of water.
• Maintain steep gradients in the kidney.
• Birds have very short loops of Henle and cannot
  concentrate urine like mammals can. They do
  produce hyperosmotic urine but conserve water by
  producing uric acid.

74

• Reptiles have only cortical nephrons and produce
  urine that is isoosmotic to body fluids.
• Epithelium of the cloaca reabsorb water.
• Excrete uric acid to conserve water as well.
• Amphibians take in water by diffusion through the
  skin.
• Excrete dilute urine and accumulate salts through
  the skin through active transport.
• On land frogs reabsorb water through bladder
  epithelia.
• Boney Salt water fish are hypoosmotic to their
  environment and have excretory tubules(no
  glomuruli or Bowmans capsule).
• Excrete small amounts of concentrated urine.