Biology 1108

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Lecture 24

• Biology 1108
• Chapter 44 Control of the Internal Environment

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Learning Objectives (1 of 3)

• Contrast
• Osmoregulation in salt water fresh water fish
• Ectotherms and endotherms
• Define
• Homeostasis
• Discuss
• Goose bumps

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Learning Objectives (2 of 3)

• Contrast
• Ammonia excretion in fish, birds, mammals
• Recall
• Maximum amount of water lost to sweat
• Functions of liver, kidneys
• Function of each part of the excretory system
• Discuss
• Seasonal dehydration
• Water bear survival
• Stone Mountain fairy shrimp

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Learning Objectives (3 of 3)

• Some words to define
• Trehalose
• Identify ALL urinary system parts

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Homeostasis

• This chapter Control of the Internal
  Environment
• Homeostasis maintenance of stability
• For today, 2 types of internal control
• Temperature (thermoregulation)
• Chemical (osmoregulation)

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Thermoregulation

• Maintenance of a certain body temperature
• Two basic types of animals
• Endotherms vs. Ectotherms

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Ectotherms

• Most of body heat comes from outside
• Often must use behavior to regulate heat
  gain/loss
• Reptiles bask in sun or on hot rock
• Fish find water suitable for body temp
• Trout prefer cold
• Bass prefer somewhat warmer

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Endotherms

• Most of heat comes from metabolism
• Examples
• Birds
• Mammals
• Great white sharks

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Endotherms Limiting Heat Loss

• Most endotherms must limit heat loss
• Thick body fat
• Feathers in birds
• Fur in mammals
• Counter current exchange

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Goose Bumps

• Each hair follicle has a tiny muscle
• When cold, muscles raise hairs
• Insulating air is trapped
• Works better for furry mammals
• We still have it as vestige of our evolutionary
  history
• Birds have similar strategy

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Counter Current Heat Exchange

• Limits heat loss through blood
• Where is it found?
• Great white shark
• Penguin legs

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How it works

• Veins and arteries close together
• Thermal energy flows from warmer to colder
• Outgoing blood warms incoming blood
• Heat stays towards bodys center

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How it Works
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Endotherms Cooling

• Sometimes cooling necessary
• Increased blood flow to skin helps
• Elephants dilate ear arteries flap
• Humans flush
• Sweating causes evaporative cooling

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Osmoregulation

• Control of internal chemical environment
• Ex Enzymes require certain pH salinity to work
  properly
• Saltwater freshwater fish must have opposite
  strategies for osmoregulation!

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Hypotonic vs. Hypertonic

• Just remember to ask, How is the outside?
• If less concentrated, then environment is
  hypotonic (lower in salt)
• If more concentrated, then environment is
  hypertonic (higher in salt)

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Freshwater Fish Ion Balance

• Constantly loses ions to hypotonic (lower salt)
  environment
• Sodium Na
• Calcium Ca
• Chloride Cl-
• To compensate
• Gills absorb ions from water
• Digestive system absorbs ions from food

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Freshwater Fish Water Balance

• In danger of having too much water
• These fish must avoid drinking
• Kidneys produce copious, dilute urine

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Saltwater Fish Ion Balance

• Fish at risk of having too many ions
• To compensate, gills constantly expel ions

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Saltwater Fish Water Balance

• Environment is hypertonic (salty)
• Will rob fish of water
• To compensate
• Saltwater fish drink lots!
• Produce very little, but concentrated urine

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Question

• Lets say youre dehydrated
• Which is absorbed by your body more quickly
• A sports drink?
• Plain water?

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Dehydration from Sweating

• Body sweats to cool skin
• Up to 2 liters per hour during heavy exercise!
• 2 loss affects performance
• Excess loss reduces blood flow to skin, sweating
  stops
• At 5, heat stroke can occur

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Seasonal Dehydration

• Problematic for aquatic or moisture-requiring
  organisms
• Strategies
• Lay desiccation-resistant eggs
• Evolve to tolerate drought

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Stone Mountain Fairy Shrimp

• Endangered species
• Stone Mountain, GA is only home!
• Live in ephemeral (temporary) pools
• All adults die when pool dries up
• Eggs resistant to dessication
• Can survive for years

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Water Bears Survive Dehydration!

• Can lose 95 of body moisture!
• Homeostasis requirement relaxed
• Remain inactive for decades
• Rehydrate in minutes
• Water bears Phylum Tardigrada

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More Amazing Feats

• Temperature -270C to 150C
• Pressure 6000atm 10km under sea!
• Pure alcohol!
• Websites
• Nature
• Tardigrade Animations

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Dehydration in Nematodes

• Some nematodes can survive dessication
• Normally, cell membranes would collapse, proteins
  would break down
• Nematodes have special sugar (trehalose) which
  prevents damage
• Trehalose used to preserve some protein-based
  pharmaceuticals

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Homeostasis Stretch
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Nitrogenous Wastes

• Proteins have many nitrogen-containing amino
  groups
• In waste products, they become ammonia
• Very toxic!
• Body must eliminate ammonia!

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Eliminating Ammonia

• Ammonia is chemically simple
• Fish excrete ammonia directly through gills,
  directly to water
• Terrestrial animals must convert ammonia to less
  toxic chemicals

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Terrestrial Animals Urea

• Mammals make urea
• Water soluble (excreted in urine)
• Disadvantage energy cost (more complex)

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Terrestrial Animals Uric Acid

• Birds, reptiles make uric acid
• Not water soluble (excreted as white paste)
• Highest energy cost (most complex)

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Excretory System

• We have 2 kidneys
• Filters blood, producing urine
• Each has 80 km of tubing!
• Tubing has semipermeable membrane
• Sorts waste molecules out of blood

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Overview of Excretory System

• Contrast ureter vs. urethra
• Ureter connects kidneys to bladder
• Urethra (with an A) connects bladder to outside
  (think, AHHHH!)

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Anatomy of the Kidney

• Contrast cortex (outer surface) vs. medulla
  (inner parts)
• Note that renal pelvis collects urine

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Anatomy of the Nephron

• Contrast filtrate vs. urine
• Filtrate removed from blood by Bowmans capsule
• Has valuable solutes, glucose
• Urine is filtrate after refining by the rest of
  the nephron
• Returns solutes, glucose to blood stream

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Nephron Details

• Filtrate goes from glomerulus, to proximal tuble,
  loop of Henle, distal tubule
• Becomes more concentrated on journey

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Dialysis

• If kidneys fail, patient must receive
  blood-cleansing treatment, or death will occur
• Dialysis machine has pump, semi-permeable tubing,
  dialyzing solution
• Treatments expensive
• Three times a week, 4-6 hours each time

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Liver

• Many homeostatic functions, including
• Changing ammonia into urea
• Converting alcohol drugs into inactive wastes
• Regulation of blood glucose levels