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Zoology 1 > Physiology 5: Water balance > Flashcards

Physiology 5: Water balance Flashcards

1
Q

Why do we regulate water?

A

The conc. of bodily fluids is usually different to that of the external environment

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2
Q

What happens a cell when there’s a lower water conc. & higher solute conc. outside

A

Cell lose water and shrivel (crenation)

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3
Q

What happens to a cell when there’s a higher water conc. & lower solute conc. inside

A

Cell will take up water and burst (lysis)

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4
Q

What is osmoregulation?

A

process that balances the uptake and loss of water
homeostatic control

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5
Q

Describe passive transport

A

along a conc. gradient (high to low)

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6
Q

Describe active transport

A

against a conc. gradient → requires energy (low to high)

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7
Q

Name 4 factors that influence the rate of passive transport (and how they do it)

A

Temperature
- Higher temp = faster rate
Size of particles
- Smaller particles = faster rate
Electrical charge of the ion
- Can prevent passage
Conc. gradient
- Greater gradient → faster rate

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8
Q

What is osmolarity?

A

measure of the osmotic pressure exerted by a solution across a perfect semi-permeable membrane compared to pure water

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9
Q

What is the osmolarity of pure water?

A

0

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10
Q

What is the equation for osmolarity?

A

(no. particles/ molecules of solute) X (moles/ litres)

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11
Q

What are the units for osmolarity

A

osmoles/litre (Osm/L)

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12
Q

Define hypo-osmotic

A

low solute conc. High water conc.

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13
Q

Define hyperosmotic

A

high solute conc. Low water conc.

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14
Q

The net flow will be from ____osmotic to ____osmotic

A

The new flow will be from hypo-osmotic to hyperosmotic

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15
Q

What does iso-osmotic mean?

A

2 solutions have equal osmolarity

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16
Q

What is saying ‘the cell is hyperosmotic to the extracellular fluid’ the same as?

A

‘the extracellular fluid is hypo-osmotic to the cell’

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17
Q

What is tonicity?

A

effect of a solution on cell volume

18
Q

What can tonicity depend on?

A
  • Solutes
  • Membrane permeability
19
Q

What’s the difference between osmolarity and tonicity?

A

Osmolarity → measure of solute conc.
Tonicity → effect of a solution on cell volumes

20
Q

Describe a hypertonic solution

A
  • Higher solute conc. outside the cell
  • Water leaves the cell via osmosis
    = cell shrivels
21
Q

Describe a hypotonic solution

A
  • Lower solute conc. outside the cell
  • Water enters the cell via osmosis
    = cell swells and eventually bursts
22
Q

Describe an isotonic solution

A
  • Same solute conc. inside and outside the cell
  • No net gain/loss of water
23
Q

Describe osmoregulators

A

→ Osmolarity of body fluids regulated to within a set range

24
Q

Give some examples of osmoregulators

A

mammals, birds, most marine and freshwater teleosts

25
Q

Describe osmoconformers

A

Osmolarity of body fluids matches that of the external environ
- Osmolarity still in a set range though → would not be 0

26
Q

Give some examples of osmoconformers

A

some fish and amphibians, freshwater and brackish invertebrates

27
Q

Describe limited osmoregulation

A

Regulate osmolarity within a certain range, but in other ranges will adjust to the external environ
- But their osmolarity is never quite the same as the external environ

28
Q

Give some examples of limted osmoregulators

A

some fish and amphibians, freshwater and brackish invertebrates

29
Q

What are the challenges of freshwater for osmoregulation?

A

Freshwater is hypo-osmitic compared to organism

30
Q

What are the challenges of saltwater for osmoregulation?

A

Saltwater is hyperosmotic compared to organism

31
Q

Marine teleosts are ____osmotic to their environ

A

Marine teleosts are hypo-osmotic to their environ

32
Q

Describe the problem marine telosts face in terms of osmoregulation

A

Too much salt:
- Due to gills high surface area, salt is gained by diffusion
- Water lost by osmosis through gills
- Water also lost because skin is permeable

33
Q

How do marine teleosts balance water loss?

A

Water (+ salt) ingested and when eating

Produce small amounts of high conc. urine to get rid of salt

Active transport of salt out through the gills

34
Q

What specialised cell do marine teleosts use to activley transport salt out of their gills?

A

Chloride cell
- lots of mitochondria

35
Q

Describe how marine teleosts activley transport salt out of their gills (7)

A
  1. Actively pump Na+ out of cell and into extracellular fluid
    = conc. gradient of Na+
  2. Na+ moves down a conc. gradient into cell
  3. Cl- is symported into the cell
  4. Na+ pumped out again, Cl- build up in the cell channels so Cl- can diffuse out passively
    • charge is built up at the basolateral surface where there’s lots of Na+
    • charge built up at the apical surface where there’s lots of Cl-
  7. Change gradient means Na+ can be pulled out through ‘leaky’ junctions between the cells
    = Net movement of Na+ and Cl- from inside the fish into the seawater
36
Q

What is the basolateral surface?

A

Faces the inside

37
Q

What is the apical surface?

A

Faces external environment or lumen of a tube (that is often invloved in absorption or secretion)

38
Q

Freshwater teleosts are ____osmotic to their environment

A

Freshwater teleosts are hyperosmotic to their environment

39
Q

Describe the problem freshwater telosts face in terms of osmoregulation

A

need more salt:
Water uptake by osmosis
Salts lost through diffusion from the gills

40
Q

How do freshwater teleosts retain/gain salt?

A

Large amounts of dilute urine
Gain salt through food
Salts and water lost in faeces
Active transport salt in through gills

41
Q

Describe how freshwater teleosts actively transport salt in via their gills

A

Basolateral Na/K ATPase pumps
→ pump Na out of the cell
Super-high affinity NA+ & Cl- transporter on apical surface
→ pumps Na+ and Cl- ions into cell from freshwater environ
Don’t have leaky junctions between cells
→ ensures little salt is lost to environ

42
Q

How are some fish able to move between marine / freshwater environs? E.g salmon

A

Close off leaky junctions between cells
Reverse ion uptake (able to switch position of pumps and symporters)
Take up more water

Zoology 1 (26 decks)

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