Control of the Internal Environment

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Control of the Internal Environment

• Ch. 25

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Objectives Define Comprehend

• Types of thermoregulation
• Endotherms vs. ectotherms
• Countercurrent heat exchanger
• Role of behavior in thermoregulation
• Metabolic rates
• Osmoregulation
• Seasonal dehydration

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Thermoregulation

• Heat is gained or lost in 4 ways
• Conduction direct transfer of thermal motion
  between molecules
• Convection transfer of heat by the movement of
  air/liquid past a body surface
• Radiation emission of electromagnetic energy
• Transfer heat between objects that are not in
  direct contact
• Evaporative cooling loss of heat from the
  surface of a liquid that is transforming into a
  gas

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Thermoregulation
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Thermoregulation
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Thermoregulation

• Endotherms and many ectotherms maintain a fairly
  constant internal temp as the external temp
  fluctuates
• Endotherms and some ectotherms alter rate of
  metabolic heat production
• Both endotherms and ectotherms change rate of
  heat gain or loss by conduction, convection,
  radiation, or evaporative cooling

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Thermoregulation

• In cold weather, mammals and birds
• Boost metabolic rate increases heat production
• How?
• Shivering increases heat produced by skeletal
  muscles
• Heat loss regulated by hair raise hairs when
  cold why?
• In some animals insulation provided by fat
• Blood flowing to skin
• vessels constrict or dilate
• Evaporative cooling panting or sweating

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Thermoregulation

• Many ectotherms
• Ex bees survive cold by clustering and shivering
• Combined metabolic activity generates enough heat
  to keep cluster alive

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Countercurrent heat exchanger
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Countercurrent heat exchanger

• Countercurrent heat exchange is important in
  controlling heat loss in many animals
• Ex birds in legs
• Ex flippers in seals, sea lions, and whales
• Ex great white sharks

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Behavior also affects body temperature

• Behavioral roles in thermoregulation

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Migration
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Penguinshuddling
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Elephants bathing
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Dressing for the weather
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Dressing for the weather
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MMM warmth through.
sunbathing
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Reduction of metabolic rate
Gray tree frog
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Reduction of metabolic rate

• Endothermy is expensive lots of food required
  to support ATP production
• When food supplies are low, some birds and
  mammals may reduce metabolic rates
• Bats exhibit torpor daily inactive during day
  and active at night
• Ground squirrels hibernate during cold weather
• A type of long-term torpor
• Live on energy stored in body fat

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Osmoregulation

• Metabolic reactions require a balance of water
  and dissolved solutes
• Ex Na, K, HCO3-
• Net movement of water from hypotonic solution to
  hypertonic solution until equilibrium is reached
• Most animals gain water from food drink
• Also lose water by urinating, defecating,
  breathing, and sweating
• Must balance the gain and loss of water
  dissolved solutes

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Osmoregulation

• Some aquatic animals are osmoconformers
• However, some ion concentrations in their body
  fluids are different than that of seawater
• Must actively transport ions into cells
• Most animals are osmoregulators
• Must use energy to control water loss/gain

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Osmoregulation freshwater fish
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Class Question

• What would happen to a freshwater fish if it was
  placed into seawater?

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Osmoregulation

• Land animals gain water by drinking and eating
• Lose from moist surfaces (lungs), urine, feces,
  and evaporation across the skin
• The problem is preventing dehydration .hmmm what
  to do.
• Insects waterproof exoskeletons
• Land verts skin, protected eggs, behavior,
  kidney

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Osmoregulation seasonal dehydration
The tardigrade
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Class Questions

• Why can a flock of geese stand on a frozen pond,
  while we could not stand on the pond without
  shoes?
• What would happen to you if you went out into the
  desert for 2 days without water? Why?

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Objectives Define comprehend

• How and why a variety of animals dispose of
  nitrogenous wastes
• Role of excretory system in homeostasis
• Path of urine through body
• Kidney functions
• How water and solutes are removed from blood
• Excretory system functions
• Role of nephrons and collecting ducts
• How filtrate becomes urine
• Liver function
• Alcohol metabolism

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Nitrogenous wastes

• Metabolism produces many toxic byproducts, for
  example those containing nitrogen
• From breakdown of protein and nucleic acids
• Must dispose of these wastes or be poisoned by
  them

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Nitrogenous wastes
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Nitrogenous wastes

• Ammonia very toxic
• soluble in water readily diffuses across
  membrane
• Mainly aquatic organisms
• Urea produced during protein breakdown in liver
  and transported by circulatory system to the
  kidneys
• Mammals, most adult amphibians, some fish
• Requires energy to produce

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Nitrogenous wastes

• Uric acid is a fairly non-toxic complex molecule
• Insoluble in water
• Avoid water-loss problem
• Excreted as paste or dry powder
• Requires energy to produce
• Birds, insects, many reptiles

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Excretory system

• Plays a vital role in homeostasis
• Forms and excretes urine
• Regulating amount of water and salts in body
  fluids

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Excretory system
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Excretory system

• Kidneys process 1,100 2000 L of blood/day
• Kidneys extract 180 L of filtrate
• Water, urea, and solutes (Na, K, HCO3-)
• Kidneys refine the filtrate and concentrate the
  urea, returning most of the water and solutes to
  the blood
• We excrete 1.5 L of urine/day

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Excretory system
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Excretory system
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Excretory System

• Blood pressure forces water and solutes from
  blood across wall of Bowmans capsule and into
  nephron
• Creates filtrate and leaves behind blood cells
  and large molecules in capillaries
• Rest of nephron
• Refines filtrate
• Distal tubule
• Collects filtrate and empties into collecting
  duct
• Filtrate then becomes urine

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Key functions of the excretory system
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Key functions of the excretory system

• Filtration water and other small molecules enter
  nephron
• Reabsorption water and solutes return to blood
• Ex glucose, salt, amino acids
• Secretion substances removed and added to
  filtrate
• Ex excess H or K
• Why H?

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Key functions of the excretory system

• Excretion urine the final product

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From filtrate to urine
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From filtrate to urine

• Water conservation is a vital part of body fluid
  homeostasis for a terrestrial animal
• Function of loop of Henle water reabsorption
• Concentration of solutes in interstitial fluid is
  higher in medulla than in cortex of kidney
  creating a solute gradient
• Water flows via osmosis to?
• Medulla
• Water carried to nearby blood capillaries
• Maintains concentration gradient

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From filtrate to urine

• As filtrate moves through the medulla
• More water reabsorbed
• Filtrate collects, forming urine, where it is
  passed into the renal pelvis
• Leaves via ureter to bladder and out the urethra

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Class Question

• Why can kidney failure lead to death?

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The liver
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The liver and homeostasis

• Among other things, the liver prepares
  nitrogenous wastes for disposal by synthesizing
  urea from ammonia
• Converts alcohol and other drugs into inactive
  products that the kidney can remove from the
  blood and excrete in urine

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The livers various roles

• Processes nutrients absorbed in small intestine
• Modify and detoxify substances
• Converts excess glucose to glycogen
• Synthesize plasma proteins
• Forms lipoproteins, which transport fats and
  cholesterol to body tissues

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Alcohol metabolism and the livernot in book

• Liver cells prefer fatty acids as fuel
• However, if alcohol is present, alcohol will be
  processed first
• Liver can metabolize ½ oz alcohol/hour
• Allows fatty acids to accumulate in liver
• Consistent heavy drinking can change cell
  structure
• Results in fatty liver
• First stage of liver deterioration
• Final, irreversible stage is cirrhosis