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biol 364 > ion & water balance > Flashcards

ion & water balance Flashcards

1
Q

what are the 3 homeostatic processes

A

osmotic regulation (osmotic pressure of body fluids)
ionic regulation (conc. of specific ions)
nitrogenous waste excretion (excretion of end-products of protein metabolism)

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2
Q

how do solutes move through water

A

by diffusion

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3
Q

what formula tells us the rate of diffusion

A

fick equation

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4
Q

fick equation

A

(dQ/dt)= DA(dC/dX)
D= diffusion coefficient
A= diffusion area
(dC/dX)= size of concentration gradient

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5
Q

water diffuses from a ___ solution to a ___ solution

A

hyposmotic solution to a hyperosmotic solution

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6
Q

what is tonicity

A

affect of a solution on cell volume

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7
Q

cells shrink in ____ solution

A

hypertonic (higher osmolarity outside than inside cell)
water leave the cell by osmosis

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8
Q

cells swell in___solution

A

hypotonic (lower osmolarity outside than inside cell)
water enters the cell by osmosis

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9
Q

cell neither shrinks nor swells in ___ solution

A

isotonic
no net osmosis

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10
Q

why is it important to regulate cell osmolarity?

A

increased intracellular osmolarity can interfere w/ cellular processes

can change cell volume

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11
Q

what does each cause?

moderate cell swelling
excessive cell swelling
excessive cell shrinkage

A

disruption of membrane
cell lysis (membrane ruptures)
macromolecular crowding

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12
Q

what do cells do to control cell volume

A

transport solutes in and out of extracellular fluid bc water follows solutes by osmosis

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13
Q

what does regulating the composition of extra cellular fluid by animals do for the cells

A

provides cells with external solution that allows them to maintain appropriate cell volume

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14
Q

what is Na+ regulated by

A

Na+/K+ ATPase and Na+/H+ exchanger

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15
Q

what is K+ regulated by

A

Na+/K+ ATPase

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16
Q

what is Cl- regulated by

A

generally distributed passively (Goldman equation)

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17
Q

what is Ca2+ regulated by

A

Na+/Ca+ antiporter
Ca2+ ATPase

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18
Q

cells usually increase their volume by actively importing which ions

A

NKCC
NA+, K+, Cl-, Cl-

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19
Q

cells usually decrease their volume by exporting which ions

A

opening K+ channels
Cl- channels also open, Cl- leaves cells in response to hyperpolarizing effects of K+ movement

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20
Q

what does water move through to get into the cell

A

aquaporins

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21
Q

ionic and osmotic challenges in marine environment

A

gaining salt and losing water

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22
Q

ionic and osmotic challenges in fresh water environment

A

lose salts and gain water

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23
Q

ionic and osmotic challenges in terrestrial environment

A

tend to lose water

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24
Q

2 strategies to meet ionic challenges

A

ionoconformer (in marine animals, little control over ion profile within the extracellular space)

ionoregulator (most vertebrates, control ion of extracellular space)

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25
Q

2 strategies to meet osmotic challenges

A

osmoconformer (internal and external osmolarity similar, marine invertebrates)

osmoregulator (osmolarity constant regardless of external environment, most vertebrates)

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26
Q

2 words describing ability to cope w/ external salinities

A

stenohaline (tolerate only narrow range)
euryhaline (tolerate wide range)

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27
Q

describe euryhaline osmoconformer

A

allows osmolarity to decrease in parallel with water until death

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28
Q

describe stenohaline osmoconformer

A

dies after very modest osmotic disruption

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29
Q

euryhaline osmoregulator

A

maintain a nearly constant internal state but eventually succumbs

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30
Q

stenohaline osmoregulator

A

can defend its internal osmolarity over a narrow range of external osmolarities

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31
Q

compatible solute

A

little affect on macromolecular function
glycerol, glucose, uncharged amino acids

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32
Q

perturbing solute

A

disrupt macromolecular function
Na+, K+, Cl-, SO4+, charged amino acids

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33
Q

counteracting solute

A

disrupt function on their own

counteract disruptive effects of other solutes when combined

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34
Q

how do animals compensate for passive ion and water movements?

A

by active transport of ions across osmoregulatory epithelia
(gills, kidney, digestive system)

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35
Q

only birds and mammals can produce ____ urine at the kidneys

A

concentrated (hyperosmotic relative to blood)

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36
Q

epithelial tissue properties for ion movement

A

asymmetrical distribution of membrane transporters
cells connected by tight junctions form a impermeable sheet of tissue

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37
Q

2 main routes of transport used by epithelial cells

A

transcellular transport (movement through the cell)
Paracellular transport (movement between cells, ‘leaky epithelia’)

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38
Q

osmoregulation in freshwater fish

A

passively gain water, loses ions across gill and gut
produces dilute urine to get rid of water
actively absorbs ions at gill

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39
Q

osmoregulation in marine fish

A

passively lose water, gain ions across gill and gut
cannot produce concentrated urine
drinks to obtain water
actively secretes ions at gill

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40
Q

what do fish gills possess to transport ions

A

ionocytes on filaments and lamellae

ionocytes generally have a lot of mitochondria + high levels of Na+/K+ ATPase activity to drive ion movement

41
Q

mechanisms of salt secretion

A

Na+/K+ ATPase creates -60mV charge
sets up condition for NKCC to enter the cell

Na+ moves back into blood via Na+/K+ ATPase
K+ re-enters blood via diffusion/leaks
Cl- moves down electrical gradient through Cl- channel from epithelium into environment
for Na+ to leave the animal, travel through Na+ specific channel between epithelial cells

42
Q

mechanisms of salt uptake

A

goal is to gain Na+ and Cl-
Na+/K+ ATPase creates -60mV charge
creates condition for Na+ uptake

Na+/K+ ATPase lets 3Na+ enter blood for 2K+
CO2 enters cell and produce H+ and HCO3-
ATP pumps out protons
HCO3- exits cell and drives Cl- uptake
Cl- doesn’t want to enter cell bc the cell is -60mV but lots of HCO3- exiting cell drives Cl- to enter
Cl- enters blood via Cl- channels

43
Q

smoltification

A

process where a juvenile salmon becomes ready for entry into marine water
metabolic changes + morphological changes + osmoregulatory system changes

44
Q

what do salt glands in birds and reptiles do?
how?

A

excrete hyperosmotic solutions of Na+ and Cl-, large amount of salt excreted in small amount of water

hyperosmotic solutions produced by ion pumps and a countercurrent multiplier

45
Q

what do rectal glands in elasmobranchs do?

A

empties into digestive tract (excreted as feces)
Na+ and Cl- actively transported from blood to lumen of gland
rate of salt excretion regulated by hormones

46
Q

ion and water balance in terrestrial habitats

A

water loss across skin, respiratory surface, and urine

water gain by metabolic water, drinking, food

rate of water loss related to surface area to volume ratio

47
Q

how does the nasal countercurrent heat exchanger work

A

incoming air is warmed and humidified

outgoing air is cooled and loses water

48
Q

how is ammonia produced and why must it be excreted

A

produced during amino acid breakdown

bc it is toxic

49
Q

3 forms ammonia nitrogen is excreted as

A

ammonia
uric acid
urea

50
Q

advantages of ammonia excretion

A

released by deamination of amino acids
requires little energy to produce

51
Q

disadvantage of ammonia excretion

A

highly toxic
requires large volumes of water to store and excrete

52
Q

why is high pH a problem for ammonia excretion?

how is the problem solved?

A

NH3 + H+ <-> NH4+

high pH-> more NH3

less NH3 will be able to enter the urine and be excreted-> less NH3 excreted

NH4+ is the more toxic form and can substitute for K+ in nervous tissue, resulting in convulsions at high levels

solution:
as NH3 moves across epithelium into (gill) water, H+ATPase also releases H+ into the water-> create NH4+ in the water

keeps NH3 levels low so NH3 can continue to move into environment

53
Q

advantage of uric acid excretion

A

few toxic effects
can be excreted in small volume of water

54
Q

disadvantage of uric acid excretion

A

expensive to produce

55
Q

advantage of urea excretion

A

only slightly toxic
relatively inexpensive to produce

56
Q

disadvantage of urea excretion

A

urea is a perturbing solute

57
Q

where is urea synthesized and where is it transported to?

A

synthesized in liver
transported by blood to kidney

58
Q

how is urea used as an osmolyte?
why does the animal need it?
how is the urea’s perturbing effect counteracted?

A

used by elasmobranchs
increases plasma osmolarity
helps prevent water loss in marine environment

perturbing effects counteracted by methylamines

59
Q

6 roles in homeostasis of vertebrate kidneys

A

ion balance
osmotic balance
blood pressure
pH balance
excretion of metabolic waste/toxins
hormone production

60
Q

2 layers of mammalian kidney
how does urine leave the kidney

A

outer cortex + inner medula

urine leaves kidney via ureter
ureter empty into bladder

61
Q

what is the nephron composed of

A

renal tubule
vasculature containing glomerulus and capillary beds

62
Q

role of glomerulus in nephron

A

ball of capillaries that provides blood to kidney to be purified

surrounded by Bowman’s capsule

63
Q

4 processes of urine production

A

FILTRATION (filtrate of blood formed at glomerulus)
REABSORPTION (specific molecules in the filtrate removed from lumen back into blood)
SECRETION (specific molecules added to the filtrate from blood)
EXCRETION (urine is excreted from the body)

64
Q

where does filtration take place

A

blood from glomerulus moves into Bowman’s capsule/ proximal tubule

65
Q

where does reabsorption take place

A

proximal tubule, loop of Henle, distal tubule

66
Q

where does secretion take place

A

proximal tubule, distal tubule

67
Q

what do foot processes provide for the glomerular capillaries

A

structural support for capillary

68
Q

why are glomerular capillaries leaky?

A

bc want water + small solutes to filter through
blood cells and large macromolecules not filtered

69
Q

what is glomerular filtration rate affected by

A

glomerular capillary hydrostatic pressure
Bowman’s capsule hydrostatic pressure
oncotic pressure (osmotic pressure dur to protein concentration)

net hydrostatic pressure drives blood filtration
osmotic pressure drives reabsorption from interstitium

70
Q

how are most water and salt in primary urine reabsorbed?

A

by transport proteins and energy

rate of reabsorption limited by number of transporters and renal threshold

each zone of the nephron has transporters for specific solutes

71
Q

what is renal threshold

A

concentration of a specific solute that will overwhelm reabsorptive capacity (no more can be reabsorbed)

eg. point at which glucose start to appear in urine

72
Q

how is glucose reabsorbed

A

by secondary transport

73
Q

how does diabetes relate to renal threshold

A

too much glucose in blood and urine

glucose too high in blood could cause metabolic issues

74
Q

what molecules are reabsorbed passively

A

Na+ and other solutes

extracellular fluid is more concentrated than fluid in the lumen-> water move out of lumen

urea become more concentrated in lumen-> urea move out of lumen into blood by passive diffusion to be transported into bladder

urea leaves later than other solutes bc want to keep urea for creation of gradient for water filtration

75
Q

what and how are molecules transported for secretion

A

removed from blood and transported into filtrate by transport proteins + energy

K+, NH4+, H+, pharmaceuticals, water-soluble vitamins

76
Q

proximal tubule function

A

most solute and water reabsorption

solutes reabsorbed by Na+ cotransport
water follows by osmosis

also carries out secretion

77
Q

loop of Henle function

A

descending limb: H2O reabsorption
ascending limb: impermeable to water, ion reabsorption

78
Q

distal tubule function

A

reabsorption completed for most solutes

79
Q

collecting duct function

A

drains multiple nephrons, carries urine to renal pelvis

80
Q

how is the osmotic gradient in the medulla created and maintained

A

loop of Henle and collecting duct act as countercurrent multipliers to create osmotic gradients that facilitate transport processes

gradients maintained by vasa recta capillaries

81
Q

what does the osmotic concentration of the final urine depend on?

A

depends on the permeability of distal tubule and collecting duct

impermeable-> dilute urine (water not reabsorbed)
permeable-> concentrated urine (water reabsorbed from collecting duct)

82
Q

mechanism for concentrating urine

A

ascending limb of loop of Henle actively pumps Na+ out of tubule lumen, Cl- and K+ follow

causes increased ion concentration in interstitial fluid of medulla
causes water to move passively out of descending limb

83
Q

how does vasa recta maintain osmotic gradient

A

ions pumped out from ascending loop

water flows out of descending tubule by osmosis

point where vasa recta enters medulla, blood is isoosmotic w/ cortex

as blood moves deeper into medulla, loses water and picks up ions from interstitial fluid (ions from ascending loop)

when blood flows back towards cortex, high plasma osmolarity causes water from descending tubule to be reabsorbed

84
Q

how does vasopressin affect the kidney

A

peptide hormone
antidiuretic hormone (reduce excretion of water)
increases water reabsorption from collecting duct
alcohol and caffeine inhibits release of vasopressin
increases cell permeability by increasing number of aquaporins

85
Q

what does aldosterone do?
what does this do to blood pressure and volume?

A

increases Na+ (and water) retention

raises blood pressure by increasing blood volume

steroid hormone

stimulates Na+ reabsorption from urine by activating transcription factor for transcription of genes for transporters

enhances K+ excretion (bc Na+/K+ exchange)

86
Q

to lower osmolarity in the kidney, it is better to…

A

get rid of Na+ than reabsorbing water

87
Q

what are the pathways that compensate for dehydration

A

dehydration= plasma osmolarity up

angiotensin II up-> vasopressin up-> H2O reabsorption by kidney

angiotensin II up-> aldosterone down-> Na+ reabsorption by kidney down-> osmolarity down

88
Q

describe the excretory control of homeostasis after water intake

A

problem-> plasma volume up, plasma osmolarity down
solution-> urine volume up-> plasma volume down-< homeostasis

89
Q

describe the excretory control of homeostasis after salt intake

A

problem->plasma osmolarity up-> salt excretion up-> plasma osmolarity down-> homeostasis

90
Q

difference between protonephridia in worms and metanephridia in molluscs + annelids

A

protonephridia: fluids taken from interstitial space into lumen w/ reabsorption, similar to vertebrate kidney tubule, mostly freshwater

metanephridia: fluid taken from blood or coelom into lumen w/ some reabsorption

91
Q

describe the malpighian tubule in insects

A

blind ending sac, empties into hind gut

primary urine formed by secretion, not filtration

reabsorption and secretion in hindgut further modifies primary urine

no ultrafiltrate is created and secretion is driven by H+ATPase

92
Q

characteristic of chondrichthian (shark) kidneys

A

extracellular fluid is slightly hyperosmotic to seawater due to high urea concentrations

countercurrent arrangement recovers up to 90% of the urea from primary urine

final urine is slightly hypoosmotic relative to shark plasma (bc urea recovered by plasma) and isotonic to sea water

Lack loop of Henle

93
Q

characteristic of fish kidneys

A

freshwater: ions reabsorbed from primary urine, excrete diluted urine, most ion + water + N+ excretion requirement met by gills and skin

Marine: small amounts of urine, some marine fish lack glomeruli, most ion + water + N+ excretion requirement met by gills and skin

ALL LACK loop of Henle

94
Q

how are amphibian kidneys different in larval and adult forms

A

larval: pronephros, empties into coelom, excrete of dilute urine (in aquatic environment)

adult: mammal-like nephron, reduce glomerular filtration rate, reabsorb water from bladder (conserve water)

95
Q

what is the biggest advantage of having a loop of Henle?

what do birds + reptiles without loop of Henle do?

A

can produce concentrated urine

longer loop of Henle and thicker medulla-> more concentrated urine

birds + reptiles without loop of Henle conserve water by excreting uric acid

96
Q

what is conservation physiology

A

scientific discipline applying physiological concepts + tools + knowledge to characterize biological diversity and ecological implications

understanding how organisms, populations, and ecosystems respond to environmental change and stressors

97
Q

what do fishes living in the high salinity lake need to worry about

A

passive ion gain and water loss

98
Q

how can one assess the salinity tolerance of a fish and what are assumptions?

A

higher salinity tolerance-> recovery of osmoregulatory status within 5 days exposure to that salinity

assumption: osmoregulatory status following 5 days is predictive of 30 days

biol 364 (6 decks)

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