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Animal Physiology > 1-6: Intro, Osmoregulation > Flashcards

1-6: Intro, Osmoregulation Flashcards

1
Q

What does surface tension do?

A

Keeps water out of where we don’t want it

Eg. breathing tubes in insects

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2
Q

How much of an animal’s body mass does water make up?

A

60-90%

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3
Q

What fluid compartments is water divided into?

A 
Intracellular fluid (ICF)
Extracellular fluid (ECF)
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4
Q

Is there more ECF or ICF in soft-bodied invertebrates?

A

ECF

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5
Q

What is ECF in vertebrates split into?

A

Plasma

Interstitial fluid

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6
Q

What is homeostasis?

A

The maintenance of a constant internal environment

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7
Q

What is the ICF high in?

A

K+, phosphates, proteins

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8
Q

What is the ECF high in?

A

Na+, Cl-

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9
Q

How does the ICF make up for the lack of Na+?

A

High K+

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10
Q

Active transporters

A

Pumps

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11
Q

Passive transporters

A

Channels

Carriers

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12
Q

3 types of carrier-mediated transport

A

Facilitated diffusion- uniport
Cotransport- symport
Countertransport- antiport

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13
Q

Why are most animal cells more negative inside compared to outside?

A

Due to an asymmetric distribution of K+

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14
Q

How is K+ maintained?

A

Na+K+ ATPase

The membrane is more permeable to K+ than other ions

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15
Q

What is the resting membrane potential?

A

-60mv

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16
Q

How is water transported across cell membranes?

A

Aquaporins

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17
Q

What are aquaporins?

A

6 membrane-spanning domain
Single polypeptide chains
13 types in mammals

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18
Q

What are aquaglyceroporins?

A

Also permeable to glycerol

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19
Q

What is osmosis?

A

The diffusion of water through a semi-permeable membrane from a region of lower total solute concentration to one of a higher total solute concentration

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20
Q

What is osmolarity?

A

The concentration of a solution expressed as the total number of solute particles per litre

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21
Q

What does the rate of osmosis depend on?

A

The osmotic permeability of the membrane

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22
Q

What is the total solute concentration?

A

The total of all the solute present

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23
Q

What is molarity?

A

The concentration in moles per litre (M)

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24
Q

What osmolarity do ICF and ECF have?

A

The same- equal osmolarity

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25
Q

What does isotonic mean?

A

Equal osmolarity

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26
Q

What does hypertonic mean?

A

Higher osmolarity

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27
Q

What does hypotonic mean?

A

Lower osmolarity

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28
Q

ECF composition in marine vertebrates

A

ECF is similar to water

Lower Na+ and Cl- due to evolutionary origin in freshwater

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29
Q

Teleost ECF

A

Hypotonic

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30
Q

Elasmobranch ECF

A

Isotonic

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31
Q

ECF composition in freshwater/terrestrial

A

ECF is like diluted seawater

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32
Q

What are osmoconformers?

A

Marine organisms that maintain an internal environment that is osmotic to their external environment
Osmolarity of cell’s is equal to osmolarity of surrounding environment

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33
Q

What are ionoconformers?

A

Same ion concentrations of ECF as the outer environment

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34
Q

What are osmoregulators?

A

ECF is kept different from environmental values

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35
Q

What is the best way to maintain constant ECF composition?

A

Seal off from the outside world

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36
Q

Unavoidable areas of uptake/loss of ions

A

Skin
Respiratory surfaces
Digestive tract
Excretory organs

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37
Q

2 distinct surfaces of a membrane

A

Apical (eg. facing gut lumen)

Basolateral (eg. ECF)

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38
Q

How are epithelia connected?

A

Tight junctions

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39
Q

Examples of epithelia involved in osmoregulation

A 
Kidneys
Urinary bladder
Malpighian tubes
Gills
Skin
Rectal glands
Nasal salt glands
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40
Q

Features of sea water

A 
Rich in NaCl
Osmolarity 1000-1150mOsm
Low in K
High in Mg and sulphate
Constant salinity at depth
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41
Q

Marine invertebrate ECF (compared to outside)

A

Isosmotic

Some ionoregulation- high K+ in squid for nerve conduction, reduced SO42- in pelagic species for buoyancy

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42
Q

Marine invertebrate ICF

A

Isosmotic with sea water

Ionic balance is different

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43
Q

Marine vertebrate groups

A

1- ECF roughly isosmotic to sea water- eg. hagfish, elasmobranchs
2- ECF osmolarity roughly a third of sea water- eg. lampreys, teleosts

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44
Q

Hagfish ECF

A

Na+ and Cl- concentration similar to seawater
Osmoconform
Ionoconform
More like marine invertebrates
Stenohaline (intolerant of brackish/dilute water)

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45
Q

Lamprey ECF

A

Na+ and Cl- in ECF 1/3rd of seawater
Euryhaline- tolerate a range of osmolarity
Migrate into freshwater

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46
Q

How do elasmobranchs make up osmotic deficit?

A

Urea and TMAO

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47
Q

What is urea?

A

End product of protein metabolism
Actively reabsorbed in kidney
Kidney holds onto urea

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48
Q

What is TMAO?

A

Another protein metabolite

Balances destabilising effect of urea on proteins

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49
Q

Osmoregulation in elasmobranchs- parts of body

A 
Digestive tract- salt uptake
Kidney- retains urea and TMAO
Gills- loss of urea and salts, water uptake
Urine- salt lost
Rectal gland- excretes excess salt
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50
Q

What is the elasmobranch rectal gland?

A

Cylindrical organ with central lumen, drains into rectum

51
Q

How does the rectal gland work?

A

Cl- accumulated in cell
Cl- efflux into the tubule lumen by secondary active transport
Secretion of isotonic NaCl
Na+ flux through tight junctions into tubule lumen

52
Q

Other examples of ureo-osmoconformers

A

Chimaeras

Coelacanths

53
Q

Teleost ECF

A

Hypoosmotic- 1/3 of sea water

No urea or other ECF osmolyte to make up the difference

54
Q

Problems with teleost ECF

A

Loss of water by osmosis (by gills)

Gain of salt (by digestive tract)

55
Q

To solve teleost ECF problems

A

Drink sea water to replace lost water
Produce minimal urine
Excrete excess salt via gills

56
Q

Teleost parts of body

A

Gills- actively excrete salt, lose water
Mouth- gain water and salt from drinking sea water
Urine- small volume of isosmotic urine produced

57
Q

Teleost kidney features

A

No loop of Henle
Can’t concentrate urine
Rich in divalent ions

58
Q

Chloride cells in teleosts

A

Large epithelial cells at the base of secondary lamellae
Packed with mitochondria
Lots of folding of basolateral membrane
For salt transport- same mechanism as elasmobranch rectal glands
Secondary active transport of Cl- across basolateral membrane
Paracellular diffusion of Na+ driven by electric potential gradient

59
Q

What volume of all water on earth is freshwater?

A

0.01%

60
Q

What can freshwater be composed of?

A

Salts from rainwater, picked up from dust as it falls

Minerals picked up from rocks- few from granite, lots from limestone

61
Q

What is the normal freshwater salt concentration?

A

0.1-10mM

62
Q

What type of water contains more ions?

A

Hard water

63
Q

Fresh water ICF

A

All maintain above the fresh water value
Some higher than others
K+ dominant

64
Q

What do you not find in freshwater?

A

Echinoderms

Cephalopods

65
Q

Freshwater ECF composition

A

Na+ and Cl- dominate

Some K+ and divalent ions

66
Q

Freshwater problems

A

Gain water by osmosis

Lose solutes by diffusion and excretion

67
Q

Freshwater solutions

A

Minimise permeable surfaces- but need for gas exchange
Produce hyposmotic urine- lose lots of water, little salts
Actively take up salts from environment- via gills and skin

68
Q

How do freshwater animals lower water permeability of external surfaces?

A

Have hard surfaces

Eg. crabs

69
Q

What are flame cells?

A

In freshwater flatworms, rotifers and nemerteans
Produce primitive urine
Found all over body

70
Q

How do flame cells work?

A

Have a flagellum that propels fluid down the duct
Cilia draws ECF through gaps between cells
Negative hydrostatic pressure sucks water in
Reabsorption of ions by tubule cell

71
Q

What are flame cells grouped as?

A

Primitive ‘kidneys’

Called protonephridia

72
Q

What are metanephridia?

A

Excretory glands found in many types of invertebrates

Eg. annelids, arthropods, mollusca

73
Q

What are coelomoducts?

A

Excretory gland and genital ducts
Wide and ciliated lumen opening into a coelom
Terminate externally by a small pore in the body wall

74
Q

What is the crayfish antennal gland?

A

The ‘green gland’
Ultrafiltrates haemolymph into a coelomosac
Reabsorption of ions in the labyrinth and canal
Minimal water reabsorption

75
Q

Basic principles of urine production

A

Energetically expensive due to reabsorption
But safe for excreting toxins
Excrete everything, reabsorb what you want to keep

76
Q

Fresh water elasmobranch features

A

A few marine species enter rivers successfully, some are exclusively fresh-water
Eg. Amazon stingray, Lake Nicaragua shark (bulls)
ECF similar to humans, very different from marine sharks
ECF doesn’t contain urea or TMAO

77
Q

Freshwater teleost features

A 
ECF around 300mOsm
Gain salt and water from feeding
Gain water from gills and body surface
Actively uptake salt via the gills
Excrete large amounts of hyposmotic urine- loss of salt
78
Q

Freshwater teleost kidneys

A

Higher filtration rate than sea water species
Similar proximal tubule function to sea water- reabsorption of vital solutes
Different distal tubule and collecting duct- NaCl reabsorption, low water permeability

79
Q

Freshwater teleost gills

A

NaCl uptake is coupled with CO2 excretion
Want to absorb as much salt as possible
Use 2 pumps- NaCl pump and proton pump at apical side

80
Q

What are catadromous fish?

A

Spawn in the sea
Young migrate up rivers for most of their life
Return to sea to spawn
Eg. freshwater eels

81
Q

What are anadromous fish?

A

Spawn in rivers
Young migrate to sea to grow
Return to rivers to spawn
Eg. atlantic salmon

82
Q

How do fish go from freshwater to seawater?

A

H+ATPase is downregulated
NaCl uptake is supressed
Increased plasma Na+ = hormone secretion
Hormones stimulate chloride cell proliferation
Increase in Na+K+ATPase activity, secretion of NaCl
Plasma Na+ levels are restored
=GILLS

83
Q

How do fish go from seawater to freshwater?

A 
Low Na+ closes tight junctions
NaCl excretion stops
Plasma prolactin levels rise, which reduce no. of chloride cells
Na+K+ATPase activity falls
Up-regulation of H+ATPase
NaCl uptake restored
=GILLS
84
Q

2 evolutionary routes onto land

A

From sea water via the littoral zone- tolerate desiccation and osmotic variations
From fresh water via swamps and bogs- produce hyposmotic urine

85
Q

What are the most successful phyla and what routes did they take?

A

Arthropods- both routes

Vertebrates- mainly freshwater

86
Q

What are interstitial fauna?

A

Small soil organisms surrounded by water film
Virtually aquatic
Eg. rotifers, nematodes

87
Q

What are cryptozoic fauna?

A

Hiding animals- larger soil organisms
High humidity
Eg. worms, centipedes

88
Q

What are hygrophilic fauna?

A

Wet-loving, moist-skinned
Require humidity
Limited tolerance of desiccation
Eg. slugs, snails, amphibians

89
Q

What are xerophilic fauna?

A

Dry-loving
Free-living above ground
Eg. insects, mammals, birds

90
Q

ECF composition of land animals

A 
200-500mOsm
Lower in ex-fresh than ex-marine
Dominance of Na+ and Cl-
High Ca2+ in some inverts
Vertebrates have ECF osmolarity of around 300, similar to freshwater fish
91
Q

What is the main form of water loss?

A

Evaporation

Called evaporative water loss (EWL)

92
Q

2 ways that water can be lost

A

Cutaneous- by skin

Respiratory- by the linings of airways, alveoli

93
Q

How is water loss increased?

A

High temperatures

Low humidity and airflow

94
Q

Behavioural adaptations to prevent water loss

A

Seek dark, damp, cool places

95
Q

How is cutaneous water permeablility reduced?

A

Dense cuticles (arthropods)
Keratinised layers of dead skin cells (tetrapods)
Lipid content

96
Q

How is water aquired?

A

Drinking-streams, dew
Diet- wet or hygroscopic foods, eg. seeds
Osmosis via other organs- abdominal skin in amphibia
Dew capture- dawn frogs in coastal deserts, condensation drains to the head
Metabolic water- from oxidative metabolism

97
Q

How is drinking controlled?

A

Increased ECF osmolarity detected by osmoreceptors, goes to hypothalamic thirst centre
Decreased ECF volume detected by volume receptors, activates renin-angiotensin system, goes to hypothalamic thirst centre

98
Q

What are kidneys/variations of kidneys for?

A

The excretion of waste products
Require a modest output of water
Main site for regulating water content and ion balance

99
Q

Nephridia in flatworms and nemerteans

A

Flame cells organised into protonephridia

Slighly hyposmotic urine

100
Q

Nephridia in annelid worms

A

Segmental nephridia
Hyposmotic urine
Each segment has its own ‘kidney’

101
Q

Nephridia in slugs and snails

A

Ultrafiltration from the pericardium
Hyposmotic urine with water is plentiful
Solid paste when water is short
Can’t produce hyperosmotic urine

102
Q

Malpighian tubes in xerophilic arthropods

A

Produce isosmotic fluid by active secretion from haemolymph
Drains into midgut
Active reabsorption of hyposmotic fluid in rectum

103
Q

What are malphighian tubules?

A

Have cation pumps at the apical membrane
Cation is K+ in herbivores, Na+ in blood feeders
Cl- moves passively via stellate cells
High water permeability

104
Q

What is the cryptonephridial system?

A 
In some beetles and lepidopteran larvae
Malpighian tubes lie close to rectum
Have an impermeable perinephric membrane
Also counter current system
Produce hyperosmotic excreta (up to 5000mOsm)
105
Q

Amphibia urine

A

Freshwater-adapted kidney
Hyposmotic urine
Salt uptake via skin

106
Q

Reptile urine

A

Isosmotic urine

Salt excretion via salt glands

107
Q

Bird urine

A

Normally hyposmotic urine
Some have salt glands
Some have loop of Henle

108
Q

Mammals

A

Most have loop of Henle

Hypo or hyperosmotic according to need

109
Q

What are salt glands?

A

Important in birds/reptiles living close to sea
Secrete hypertonic NaCl
Can be in eye sockets, nasal cavity, mouth, top of skull
Similar mechanism to rectal glands and chloride cells

110
Q

Main principle of the mammalian kidney

A

Ultrafiltration

Selective reabsorption/secretion

111
Q

What does too little sodium cause?

A

Collapse in the circulatory system

112
Q

How is the kidney able to produce hyperosmotic urine?

A

Due to the loop of Henle

113
Q

What cannot pass through into the filtrate?

A

Blood cells

Proteins

114
Q

What is the filter in the glomerulus

A

Basement membrane of the capillary endothelium

115
Q

What happens in the proximal convoluted tubule?

A

Isosmotic reabsorption of 75% of NaCl and water

Concentration of waste products eg. urea

116
Q

What happens in the descending limb of the loop of Henle?

A

Passive reabsorption of water

117
Q

What happens in the thick ascending limb of the loop of Henle?

A

Active reabsorption of NaCl

118
Q

What happens in the distal convoluted tubule?

A

Aldosterone-regulated reabsorption of Na+

119
Q

What happens in the collecting duct?

A

ADH-regulated reabsorption of water

120
Q

How does the loop of Henle create a hyperosmotic ECF in the inner medulla?

A

Osmotic water efflux from descending limb
Passive salt efflux from thin ascending limb
Active salt transport out of thick ascending limb

121
Q

What does ADH do?

A

Causes an organism to retain water

122
Q

Kangaroo rat water

A

Survive without drinking
Produce small volumes of very hyperosmotic urine
Water gained from metabolism
Unavoidable loss by evaporation

123
Q

Marine mammal water

A 
Whales, porpoises etc
Drink little sea water
Water intake is mainly from diet
Do not have salt glands
Hyperosmotic urine

Animal Physiology (3 decks)

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