1-6: Intro, Osmoregulation Flashcards Preview

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

Flashcards in 1-6: Intro, Osmoregulation Deck (123):
1

What does surface tension do?

Keeps water out of where we don't want it
Eg. breathing tubes in insects

2

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

60-90%

3

What fluid compartments is water divided into?

Intracellular fluid (ICF)
Extracellular fluid (ECF)

4

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

ECF

5

What is ECF in vertebrates split into?

Plasma
Interstitial fluid

6

What is homeostasis?

The maintenance of a constant internal environment

7

What is the ICF high in?

K+, phosphates, proteins

8

What is the ECF high in?

Na+, Cl-

9

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

High K+

10

Active transporters

Pumps

11

Passive transporters

Channels
Carriers

12

3 types of carrier-mediated transport

Facilitated diffusion- uniport
Cotransport- symport
Countertransport- antiport

13

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

Due to an asymmetric distribution of K+

14

How is K+ maintained?

Na+K+ ATPase
The membrane is more permeable to K+ than other ions

15

What is the resting membrane potential?

-60mv

16

How is water transported across cell membranes?

Aquaporins

17

What are aquaporins?

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

18

What are aquaglyceroporins?

Also permeable to glycerol

19

What is osmosis?

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

20

What is osmolarity?

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

21

What does the rate of osmosis depend on?

The osmotic permeability of the membrane

22

What is the total solute concentration?

The total of all the solute present

23

What is molarity?

The concentration in moles per litre (M)

24

What osmolarity do ICF and ECF have?

The same- equal osmolarity

25

What does isotonic mean?

Equal osmolarity

26

What does hypertonic mean?

Higher osmolarity

27

What does hypotonic mean?

Lower osmolarity

28

ECF composition in marine vertebrates

ECF is similar to water
Lower Na+ and Cl- due to evolutionary origin in freshwater

29

Teleost ECF

Hypotonic

30

Elasmobranch ECF

Isotonic

31

ECF composition in freshwater/terrestrial

ECF is like diluted seawater

32

What are osmoconformers?

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

33

What are ionoconformers?

Same ion concentrations of ECF as the outer environment

34

What are osmoregulators?

ECF is kept different from environmental values

35

What is the best way to maintain constant ECF composition?

Seal off from the outside world

36

Unavoidable areas of uptake/loss of ions

Skin
Respiratory surfaces
Digestive tract
Excretory organs

37

2 distinct surfaces of a membrane

Apical (eg. facing gut lumen)
Basolateral (eg. ECF)

38

How are epithelia connected?

Tight junctions

39

Examples of epithelia involved in osmoregulation

Kidneys
Urinary bladder
Malpighian tubes
Gills
Skin
Rectal glands
Nasal salt glands

40

Features of sea water

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

41

Marine invertebrate ECF (compared to outside)

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

42

Marine invertebrate ICF

Isosmotic with sea water
Ionic balance is different

43

Marine vertebrate groups

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

44

Hagfish ECF

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

45

Lamprey ECF

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

46

How do elasmobranchs make up osmotic deficit?

Urea and TMAO

47

What is urea?

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

48

What is TMAO?

Another protein metabolite
Balances destabilising effect of urea on proteins

49

Osmoregulation in elasmobranchs- parts of body

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

50

What is the elasmobranch rectal gland?

Cylindrical organ with central lumen, drains into rectum

51

How does the rectal gland work?

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

Other examples of ureo-osmoconformers

Chimaeras
Coelacanths

53

Teleost ECF

Hypoosmotic- 1/3 of sea water
No urea or other ECF osmolyte to make up the difference

54

Problems with teleost ECF

Loss of water by osmosis (by gills)
Gain of salt (by digestive tract)

55

To solve teleost ECF problems

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

56

Teleost parts of body

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

57

Teleost kidney features

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

58

Chloride cells in teleosts

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

What volume of all water on earth is freshwater?

0.01%

60

What can freshwater be composed of?

Salts from rainwater, picked up from dust as it falls
Minerals picked up from rocks- few from granite, lots from limestone

61

What is the normal freshwater salt concentration?

0.1-10mM

62

What type of water contains more ions?

Hard water

63

Fresh water ICF

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

64

What do you not find in freshwater?

Echinoderms
Cephalopods

65

Freshwater ECF composition

Na+ and Cl- dominate
Some K+ and divalent ions

66

Freshwater problems

Gain water by osmosis
Lose solutes by diffusion and excretion

67

Freshwater solutions

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

How do freshwater animals lower water permeability of external surfaces?

Have hard surfaces
Eg. crabs

69

What are flame cells?

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

70

How do flame cells work?

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

What are flame cells grouped as?

Primitive 'kidneys'
Called protonephridia

72

What are metanephridia?

Excretory glands found in many types of invertebrates
Eg. annelids, arthropods, mollusca

73

What are coelomoducts?

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

74

What is the crayfish antennal gland?

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

75

Basic principles of urine production

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

76

Fresh water elasmobranch features

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

Freshwater teleost features

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

Freshwater teleost kidneys

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

Freshwater teleost gills

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

What are catadromous fish?

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

81

What are anadromous fish?

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

82

How do fish go from freshwater to seawater?

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

How do fish go from seawater to freshwater?

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

2 evolutionary routes onto land

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

85

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

Arthropods- both routes
Vertebrates- mainly freshwater

86

What are interstitial fauna?

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

87

What are cryptozoic fauna?

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

88

What are hygrophilic fauna?

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

89

What are xerophilic fauna?

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

90

ECF composition of land animals

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

What is the main form of water loss?

Evaporation
Called evaporative water loss (EWL)

92

2 ways that water can be lost

Cutaneous- by skin
Respiratory- by the linings of airways, alveoli

93

How is water loss increased?

High temperatures
Low humidity and airflow

94

Behavioural adaptations to prevent water loss

Seek dark, damp, cool places

95

How is cutaneous water permeablility reduced?

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

96

How is water aquired?

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

How is drinking controlled?

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

What are kidneys/variations of kidneys for?

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

99

Nephridia in flatworms and nemerteans

Flame cells organised into protonephridia
Slighly hyposmotic urine

100

Nephridia in annelid worms

Segmental nephridia
Hyposmotic urine
Each segment has its own 'kidney'

101

Nephridia in slugs and snails

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

102

Malpighian tubes in xerophilic arthropods

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

103

What are malphighian tubules?

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

What is the cryptonephridial system?

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

Amphibia urine

Freshwater-adapted kidney
Hyposmotic urine
Salt uptake via skin

106

Reptile urine

Isosmotic urine
Salt excretion via salt glands

107

Bird urine

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

108

Mammals

Most have loop of Henle
Hypo or hyperosmotic according to need

109

What are salt glands?

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

Main principle of the mammalian kidney

Ultrafiltration
Selective reabsorption/secretion

111

What does too little sodium cause?

Collapse in the circulatory system

112

How is the kidney able to produce hyperosmotic urine?

Due to the loop of Henle

113

What cannot pass through into the filtrate?

Blood cells
Proteins

114

What is the filter in the glomerulus

Basement membrane of the capillary endothelium

115

What happens in the proximal convoluted tubule?

Isosmotic reabsorption of 75% of NaCl and water
Concentration of waste products eg. urea

116

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

Passive reabsorption of water

117

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

Active reabsorption of NaCl

118

What happens in the distal convoluted tubule?

Aldosterone-regulated reabsorption of Na+

119

What happens in the collecting duct?

ADH-regulated reabsorption of water

120

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

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

121

What does ADH do?

Causes an organism to retain water

122

Kangaroo rat water

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

123

Marine mammal water

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