Osmoregulation - PowerPoint

Document Sample
Osmoregulation - PowerPoint Powered By Docstoc
					Osmoregulation

    BIO 202
Objectives
1. Distinguish between osmoregulators and osmoconformers
2. Discuss problems faced by organisms in marine, freshwater, and terrestrial
          environments in respect to osmoregulation. What are some adaptations that
          have evolved to meet these challenges?
3. Discuss the evolutionary changes in the regulation of water and wastes, from
          invertebrates to insects to complex vertebrates.
4. Identify and give the function of all the structures in the mammalian excretory system,
          include the nephron.
5. Discuss how the nephron functions.
6. What are structural and physiological adaptations of the kidney to different
          environments?
7. Explain correlation of type of nitrogenous waste and how this can be dealt with by
          different organisms
8. What are advantages of endothermy?
9. How do terrestrial mammals maintain a relatively constant body temperature?
10. How do other organisms (other than mammals) deal with thermoregulation?
You are responsible for knowing how the nephron functions: you should be able to
          discuss how blood is filtered in the glomerulus, what substances are secreted
          into or pulled out of the nephron at each area (proximal tube, loop of Henle,
          distal tube, and collecting duct). Substances that are of importance are salts,
          proteins, water, hydrogen ions, and bicarbonate ions. This understanding will
          be aided by knowing the structure of the nephron: including cortex, medulla,
          urinary bladder, ureter, urethra, glomerulus, glomerular capsule, proximal
          tubule, loop of Henle (intermediate tubule), distal tubule, and collecting duct.
• Organisms live in salt water,
  fresh water, land; each
  posses a different challenge
  for balancing water retention
  and salt concentration
• evolved from the water and
  this reflects their origin
•     conserve or excrete water




Kidneys have evolved in conjunction with reproductive
  system develop from adjacent tissues - kidney
  usually 1st and reproductive organs tap into kidney
  or derivatives
• Urinary system functions in the elimination of
  waste products (usually ammonia), and in the
  regulation of water and electrolytes
• Cellular metabolism produces CO2, water, N
  wastes that diffuse into interstitial fluid
• also have organic acids, phosphates, sulfate
  ions, etc that are produced


• Gain or loss of ions: fresh water, salt water, land
• interstitial fluid remains fairly constant despite all
  the changes
• Osmoregulation
  – Balancing chemical composition.
    • Changes in WATER & SOLUTES
    • conserve or excrete water
• Excretion
  – Getting rid of excess
    • Water and Nitrogenous wastes
    • Bad products (poisons, etc.)
    • Excess of some products (sugars, salts, etc.)
• Moves across transport Epithelium
  – With or against gradients (ATP dependent)
         Nitrogenous Waste
• By product of metabolic activity
  – Typically starts as - NH2 (amino)
  – Combines with H+ to form Ammonia – NH3
  – Excreted in a variety of forms
  – Water availability dependent
• Homeostasis by excretion and
  osmoregulation
• CO2 and H2O are products of
  carbohydrate and fat metabolism
   – easily eliminated
• N - harder to get rid of
   – forms NH3 which is highly toxic
• Ammonia
  – TOXIC
  – Lots of water to
    excrete (dilute)
  – Aquatic species
  – NH4+ ion
• Urea
  –   Produced in LIVER
  –   Energetically costly
  –   Low toxicity
  –   Water soluble
  –   Transport in high
      concentration
   (less water needed)
• Uric Acid
  –   Low toxicity
  –   Water Insoluble
  –   Solid like excretion
  –   VERY costly
  –   Important in
      SHELLED eggs
Switching between N waste forms..
• Change in lifestyle
  – Tadpole (NH3) to Frog (urea)
• Change in water availability
  – Wetter (urea) to Dry (uric acid)
 • STORY: DID THE FIRST VERTEBRATE
       ORIGINATE IN FRESHWATER OR
                   SEAWATER?
• 500 million years ago: freshwater had no
  multicellular organisms
   – no predators
   – no competitors
   – the vertebrate kidney indicates
     freshwater
• BUT: all the protochordate fossils (found
  at this point in time) indicate a marine start
    •    STORY: DID THE FIRST VERTEBRATE
            ORIGINATE IN FRESHWATER OR
                       SEAWATER?
•   Hagfish, the most primitive living vertebrate have
    blood and glomerular filtration similar to marine
•   There are invertebrates w/o a freshwater history.
•   They are true osmoconformers: Ca, PO4, Mg,
    SO4 are all regulated like marine invertebrates
•   They have primitive regulation of Na and Cl as do
    marine inverts
•          These are ion secreting cells
•   BUT…. They also have some freshwater features
•   A glomerular kidney with a large volume of dilute
    urine excreted
•                    The tubules reabsorb Na
•   Gills and skin are less permeable to NaCl than
    marine inverts
•   Gills have ion pumps that uptake Na Cl and
    exchange H+/HCO3-
•   Why do hagfish, our model early vertebrate, have
    freshwater features???
      Osmoregulation
• osmoconformers
• osmoregulators
• 2 problems:
  –1) need enough Na  +
   for nervous system
  –2) metabolism needs
    Balancing water and solutes
• Osmolality – concentration of solutes in solution
• Three internal conditions:
   – Isoosmotic – same osmolality as surroundings
   – Hyperosmotic – higher osmolality than surroundings
   – Hypoosmotic – lower osmolality than surroundings
• Water flows from lower osmolality to higher.
• often couple water removal and waste removal
• Osmoregulator
   – keeps osmolality different than surroundings
• Osmoconformer
   – osmolality similar to surroundings

   – Which is more costly????
      • OSMOREGULATOR ---- ACTIVE TRANSPORT
• Osmoconformer
  – Marine invertebrates
  – Hagfish
  – Shark**
     • Isotonic by keeping high urea concentration
~ ISOTONIC to seawater




High UREA concentration in body fluid
Salts still removed – RECTAL GLAND
           Regulate or conform?
• Depends on where
  you live:
• Freshwater = hyperosmotic -
  osmosis into organism, prevent
  self dilution
• Fish: 90% of ammonia waste
  is as NH3, rest as urea
   – blood NaCl is 30-40% more
      than seawater
   – gills secrete 6 times more
      than kidney
   – copious, dilute urine -
      therefore need kidney
• Protozoa: contractile vacuoles
  to pump out water
                        Regulate or conform?
•    Marine = hypoosmotic - water
    leaves organism, prevent
    dehydration
•   low total solutes
•    gills already work - what are
    the use of kidneys?
•   some have lost glomerular
    filtration
•   High energy cost to lower to
    lower than seawater
•   Are these salt concentrations a
    historic consequence of
    freshwater heritage?
•   Ureosmotic:
      – use urea to balance the
         concentration of seawater
      – Sharks = a type of
         osmoconformers
       Regulate or conform?
•   Land: lose water by evaporation
•   osmoregulators
  How osmoregulation is achieved
• Freshwater
• invertebrates use nephrid
  organs - water across a
  membrane
•  collecting organs
•  then expelled by a pore
• membrane = filter to retain
  proteins and sugars
  How osmoregulation is achieved
• Insects have Malphigian
  tubules - tubular
  extensions of the
  digestive tract
• branch off before hindgut
• K+ secreted into tubules
  and water follows due to
  osmotic gradient
• membrane to retain
  proteins etc
• very efficient
• from endoderm not
  mesoderm as in
  vertebrates
  How osmoregulation is achieved
• Marine
• sponges and protists - use
  contractile vacuoles
• many invertebrates are
  osmoconformers
• sharks - pump salt out
  rectal glands and retain
  urea
   – causes lower osmolarity
     then sea water
   – use TMAO
     (trimethylamine oxide) to
     buffer urea
   – can tolerate higher levels
     than most vertebrates
   – gills impervious to urea
     loss
   How osmoregulation is achieved
• Marine
• bony fishes - hypoosmotic - drink lots and excrete salt out gill
  epithilia
• birds and reptiles - salt glands to get rid of salt
• found in the nasal, orbital, sublingual, or tongue surface regions
• eat salty foods or ingest seawater
• have extra salt to deal with more than the kidney could excrete
• secrete salt at various times
  How osmoregulation is achieved
• Anhydrobiotics - survive
  drying up of habitat
• Tardigrades = water bears or
  moss piglets
• like onchyphorans and
  arthropods except cuticle is
  proteins not chitin
• hydrated = 25% water
• If decrease surrounding water
  and tissues dry up also
• use trehalose (a disaccharide)
  to replace lost water in
  membranes and proteins
• prevents distortion of cell
  structures during dehydration
• can survive many years
 How osmoregulation is achieved
• Freshwater fishes
• high pressure kidneys produce large
  volumes of filtrate
• reduce water entry - mucus
  epidermis, do not drink water
 Fresh water or saltwater kidney to
          go onto land?
• hagfishes - osmoconformers like marine invertebrates
• unlike most marine vertebrates
• members of the oldest surviving vertebrate group
    – the cyclostomes
• BUT…possess a filtration kidney, yet live in salt water
• if freshwater is the origin
    – hagfishes would live in freshwater
• if seawater is correct
    – hagfishes would osmoregulate like other vertebrates
• have had a long period of time to diverge from the
  ancestral form
  How osmoregulation is achieved
• Terrestrial
• many die if dehydrate  protective outer
  layers
   – Arthropods - outer cuticles – waxy
   – snails - shells
   – vertebrates - keratinized skin
• eat moist foods
• active only at night
• excretory organs conserve water
• selective reabsorption of ions and molecules
• membranes to filter are varied w/
  environment and organism
            Water loss on land
• Hard protection
  – Insects, snails, etc.
• Leathery protection
  – SKIN
• Behavioral conservation
  – Nocturnal (cooler)
• Drinking
• Metabolic water
• Reabsorbing
Vertebrate Kidney
             Excretory systems
Water and Solutes

                           Non-selective




                             Selective
              URINE:
• Contains:
  – WATER
  – UREA
  – NaCl
  – H+ ions
  – DRUGS & POISONS
  – EXCESS PRODUCTS….
~ 5 liters of blood

- passes through
kidney ~ 400x /day

~ 2000 liters of blood

~ 160 liters filtered out
into Bowman’s capsules
~ 1-2 liters urine/day

~ 158 liters reabsorbed
Glomerulus
POSTERIOR
Antagonistic hormone Atrial natriuretic Factor (ANF)
    Evolution of the kidney
• Protonephridia = 1st little kidney
   – inner sac is capped and lined
     with special cells
   – seen in bilateral symmetry
   – flame cells in the flatworm, ribbon
     worms
   – tissues more saline than
     environment
   – direct control of interstitial fluid
   – branched system throughout
     body
   – fluid drains into ducts that
     terminate in flame cells with cilia
     or flagella
   – cilia create negative pressure
   – possibly also secrete N wastes
     usually use body surface for
     majority
   Evolution of the kidney
• Metanephridia - 2nd (later) little kidney
  – tubule opens via funnel or pore
  – Found in earthworms (coelomates)
  – drain water from coelomic cavity
  – pairs in each segment
  – ectodermal origin
  – internal openings (funnels) to collect
    body fluids and external pores
  – nephrostome collects body fluid -->
    stored in storage bladder enveloped
    by caps
Metanephridia
     Evolution of the kidney
• Birds and Mammals
    – higher metabolism and endothermy
    – more N waste made
•   also have water loss through respiration and skin
•   increased number of renal tubes
•   allows removal of N waste from a large volume of plasma
•   heart structure  higher filtration pressure
•   mammals - have the loop of Henle added in
    – with descending and ascending
    – thick = cuboidal epithelial cells
    – thin = squamous cells
• Loops of Henle occur only in organisms that are capable of
  producing urine more concentrated than blood
• mammals produce urine 2-25% as concentrated as plamsa
•   Mollusks
                                        Cool Adaptations
     – kidney organ that also aid in
        gamete secretion
•   Crustaceans - antennal or green glands
     – also use gills and areas of the body
        where the cuticle is thin
•   Amphibians
     – first terrestrial organisms
     – kidney like freshwater fishes - stay
        in wet places on land
     – some larval forms have a
        nephrostome
     – some live in freshwater - like fishes
     – If water is in short supply - excrete
        N as urea
     – skin also
     – some anurans (frogs) live in low
        water - retain large amount of urea
     – dessert - excrete N as uric acid
          • or may store water in lymph
             sacs - up to 2 years
                     Cool Adaptations
• African lungfish
• normal in rivers and streams as it swims
• during drought it estivates converts
  ammonia to urea
• rain returns and takes up water and then
  secretes urea
• Reptiles                     Cool Adaptations
    – Often found in dry places
• freshwater - like freshwater fishes
• marine - use salt gland to get rid of
  extra salts
• terrestrial - reabsorb much water
  from kidney
• urine never more
  concentratedentrated than blood
  plasma
    – or else lose water from blood
    – ammonia  less toxic urea or
       uric acid
• uric acid leaves via cloaca as
  whitish paste like
• skin reduces water loss
• glomeruli and reduced tubular
  filtration - low water loss
                        Cool Adaptations
• Birds and Mammals
• beaver has short loops -
  urine 2x's as concentrated
  as blood
• desert rodents - urine
  25x's as concentrated as
  blood
   – remove more water than
     reptiles or amphibians
• camel 8x's more
  concentrated than plasma
• mouse 22'x more
  concentrated than plasma
Cool Adaptations

Cool Marine Birds...

     Salt
    Glands
    STORY CONTINUED
• Why do hagfish have freshwater features?
• Preadaptation to go to freshwater?
• Strictly marine
• No bone – no need for salts to make bone
• Low BP – a filtration kidney would be hard
• De-evolution to ion regulation?
• But why the energy cost??
• Only part that points to seawater heritage is the
  ion concentration– all else says fresh
• The Na+/H+ and Cl-/HCO3- pumps can be
  accounted for to excrete excess acid
  So what is the origin of the terrestrial
 vertebrate kidney – fresh or seawater?
• Filter feeding pre-vertebrate
  chordates lived in freshwater and
  osmoregulated
•       Complete with low blood ions,
  kidneys, and branchial ion pumps
•       Still low food sources in
  freshwater
             – return to sea: especially
               when bigger
• Anadromy: (seen in lampreys,
  sturgeon, bass, salmon..)
   – Breed in freshwater: filter
      feeders
   – Adults go to sea and become
      predators (except lampreys….
      Parasites on other fish)
                                        Maybe….
• Hagfish types went back to
  seawater after reached adulthood
   – (remember only example we
     have are of adults….. no idea on
     juveniles)
• Anadromous organisms need
   – Increased cephalization and
     special senses….
       • deal with flowing freshwater
       • Salmon and lampreys use
         smell to locate juvenile
         breeding ground
       • Increased metabolic needs….
       • Swim: fresh  sea  fresh
       • Increased endocrine……
         growth (not to big to swim,
         yet big enough)
   – Development (juvenile in fresh,
     adult in sea)
   – Reproduction – only when ready
     to return
  Temperature Regulation
• Transfer from organism to environment
   – Conduction - thermal motion of molecules –
     heat
      • water better than air
   – Convection - mass flow of air or liquid past
     body
      • breezes and wind chill
   – Radiation - emission of electromagnetic waves
      • warmed by sun
   – Evaporation - loss of heat from liquid surface
      • loss of gas
      • sweat
 Temperature Regulation
• Mechanisms
 –skeletal muscle activity
 –vasodilation and constriction
 –evaporation - respiration,
  sweating, saliva, urine
 –behavior - cooler area
    Temperature Regulation
•   Adaptations
     – Birds - no sweat glands
         • panting to cool
         • prevent heat loss - feathers and blood flow in
            legs - counter current exchange
     – Marine mammals - water cooler than body
         • layer of fat – blubber
         • counter current exchange in fins
     – Reptiles - ectotherms
         • Behavior
         • thermogenesis - shivering
     – Amphibians - produce little heat and lose it easily
         • Behavior
         • mucus - regulate cooling
     – Fish – ectotherms
         • countercurrent in swimming muscles
     – Inverts
         • behavior - desert
         • Flying
         • thorax - maintains heat
         • social organization - honey bees
•         B. How osmoregulation is achieved
•                  often couple water removal and waste removal
•                  1. Freshwater
•                              inverts use nephrid organs - water across a membrane
•                                           --> collecting organs --> then expelled by a pore
•                                           membrane = filter to retain proteins and sugars
•                              fish - excrete large amounts of dilute urine
•                                           lose salts - regain via diet or Na+ or Cl- pump
•                              Salmon- live in fresh and salt water - depends upon env.
•                  2. Insects have Malphigian tubules - tubular extensions of the digestive tract
•                              branch off before hindgut
•                              K+ secreted into tubules and water follows due to osmotic gradient
•                              membrane to retain proteins etc
•                              very efficient
•                  3. Marine
•                              sponges and protists - use contractile vacuoles
•                              many inverts are osmoconformers
•                              hag fish is iso-osmotic - primitive form
•                              sharks - pump salt out rectal glands and retain urea
•                                           causes lower osmolarity then sea water
•                                                        uptake large amounts of water and pee
    constantly
•                                           use TMAO (trimethylamine oxide) to buffer urea
•                                           can tolerate higher levels than most vertebrates
•                                           gills impervious to urea loss
•                              bony fishes - hypoosmotic - drink lots and excrete salt out gill epith
•                              birds and reptiles - salt glands to get rid of salt
•                                           eat salty foods or ingest seawater
•                                           have extra salt to deal with more than the kidney could
•                                           secrete salt at various times