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physiology - mb > Salinity > Flashcards

Salinity Flashcards

1
Q

salinity regulation within invertebrates

A

bladder -> tubule -> labrynth -> end sac
osmoconformers

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2
Q

salinity regulation within bony fish

A

osmoregulation is very similar to mammalian osmoregulatory systems (glomerulus etc)

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3
Q

Why regulate salinity

A
  • Important within muscle fibres that facilitate contraction and relaxation – muscle cramp caused by imbalance of ion balance within tissues
  • Therefore we need to regulate electrolytes
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4
Q

osmoregulation

A

maintains electrolyte and fluid homeostasis by active regulation of osmotic pressure of bodily fluids

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5
Q

excretion

A

process of getting rid of metabolic waste

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6
Q

Ammoniotelic animals

A

most aquatic animals secrete ammonia unlike mammals and cartilaginous fish that excrete urea

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7
Q

requirement of excreting ammonia

A

Excretion of ammonia requires water.

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8
Q

How is ionic and osmotic composition linked to excretion

A

Regulation of the ionic and osmotic composition of body fluids is intimately linked with nitrogenous excretion – osmosis is a key process within this excretion
* Isosmotic situation is the most desirable

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9
Q

marine invertebrate fluid composition

A

-Similar composition to that of the sea water around them
-Osmotic concentration is close to their medium and do not experience significant water loss or gain

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10
Q

Osmoconformers

A

Overall osmotic concentration is always approximately isosmotic (same osmotic pressure) with seawater

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11
Q

Strategies of osmoconformity

A
  • Body volumes changes as water enters and leaves by osmosis at least in the short term
  • In the long-term, volume may adjust towards original level as both ions and water move
  • Cell volume tends to be slowly adjusted by regulating free amino acid pool
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12
Q

Osmoregulators

A
  • Regulate ionic and osmotic compositions of their body fluids to maintain a stable internal fluid composition
  • Migratory fish and some estuarine invertebrates
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13
Q

Euryhaline animals

A
  • Tolerate a wide range of salinities – combo of osmoconforming and osmoregulatory processes
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14
Q

Stenohaline

A
  • Restricted to a narrow salinity range
  • Still have active ionic and osmotic regulators
  • Most marine organisms
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15
Q

Intracellular osmotic regulation

A
  • Cells are isosmotic to bodily fluids but have a different ion composition
  • If osmotic conc of body fluid changes this is matched by changes of organic molecules in cells
  • Organic molecules are used inside cells as osmoregulators
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16
Q

Marine invertebrate intracellular regulation molecule

A

the amino acid glycine

17
Q

Conflict of using amino acids as osmotic regulators

A
  • May interact with proteins and change their conformation
  • Enzymes and other proteins are sensitive to change in ionic composition of the intracellular fluids
18
Q

amino acids - Salinity mediated osmoregulation

A
  • Conc of free amino acids in cells is regulated by changing levels of protein degradation or synthesis
  • Concentration increases during salinity stress
  • Salinity induced alterations in amino acid bases are caused by adjustments consistent with cell volume regulation
19
Q

Marine vertebrates ways of osmotic regulation

A
  • Isosmotic with sea water
  • Hypoosmotic regulators (most vertebrates)
  • Air breathing marine vertebrates (no gills)
20
Q

Hypoosmotic – marine teleost

A
  • Body fluid of teleost only ¼ to 1/3 of seawater concentration in both seawater and freshwater species
  • Marine teliosts lose water by osmosis from gills but compensate by drinking water
  • Excess nacl secreted at gills
  • Active transport of cl- by large chloride cells in gill epithelium and Na+ follows passively
  • Fish kidneys cannot form conc urine but excrete divalent ions Mg+2 and SO42- (with minimal loss of water -> small volume of isotonic urine)
21
Q

Salmon - hypoosmotic

A
  • Salmon migrate between oceans and freshwater
  • At sea – drink seawater, excrete salt from gills and produce little urine
  • In freshwater – stop drinking, take in salt via gills and produce lots of dilute urine (hyperosmotic that why they stop drinking)
22
Q

Air breathing marine vertebrates

A

Essentially operate as terrestrial for osmoregulation – isolated from seawater as no gills
* Face more problems than fully terrestrial species as no freshwater to drink & high salts in food (algae & invertebrates isosmotic to seawater)

23
Q

Marine mammals

A
  • Able to form hyperosmotic urine (more conc than seawtaer)
  • ALLOWS REMOVAL EXCESS of salts from food or ingested seawater
  • Humans cannot tolerate this
  • Whale has net gain of 1/3 litre water, while human has net loss of 1/3 litre water if human drinks seawater
  • Human urine is less concentrated than seawater, so drinking it hastens death
24
Q

Mechanism of excretion in invertebrates

A
  • Lower invertebrates still rely on diffusion to remove nitrogenous waste
  • Higher invertebrates have a tubular filtration system
25
Q

3 basic processes that occur in a tubular system

A

reabsorption filtration and excretion

26
Q

excretory system overview

A
  • Systems of tubules are spread throughout the body
  • Beating cilia at the closed end of the tube draw intestinal fluid into the tubule
  • Excess fluid exits through skin
  • Solutes are reabsorbed before dilute urine is excreted
27
Q

More complex excrete systems

A
  • Simple tubular excretory system
  • Internal openings or nephrostomes collect coelomic fluid when the cilia present on the funnel shaped opening beat
  • Metanephridia have both excretory and osmoregulatory functions
  • Excrete water, mineral, salts and nitrogenous waste in the form of urea
28
Q

Crustacea excretory system

A
  • Antennal gland consists of a bulb like sac (‘end sac’) called the ‘coelomosac’ connected to the ‘labyrinth’ – a narrow tubular ‘nephridial canal’ joins the labyrinth and a bladder
  • Structures are also osmotically active – urine (ammonia) is first formed in the lumen of the coelomosac and is sent out through the bladder at the base of the second antenna
29
Q

What is the approximate osmotic concentration of the body fluids of an
osmoregulating fish?

A

~ 200mM Na+ in teleosts, balance of osmotic pressure sometimes maintained with
urea to 600-700mM

physiology - mb (10 decks)

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