Renal Physiology IV - Water and Electrolyte Balance

Question 1

water is the major constituent of:

Answer 1

blood
lymphatic fluid
cerebrospinal fluid
aqueous humour
milk and colostrum
saliva
tears
sweat
bile
semen and secretions of sexual accessory glands

Question 2

species difference - water balance?

Answer 2

dry climate animals have smaller faecal and urinary losses. some species can derive all the water they need from metabolic water

Question 3

how can water be lost?

Answer 3

insensible losses (skin and lungs)
faecal loss
urinary loss

Question 4

how can water be gained?

Answer 4

food and drink (90%)
metabolism (-10%)
(glucose, O2, CO2, H2O + ATP)

Question 5

water intake needs to =

Answer 5

water loss
if not then there is disorder

Question 6

what are elctrolytes?

Answer 6

these are minerals in your body that have an electric charge

Question 7

where are electrolytes found?

Answer 7

in blood, urine, tissues and other body fluids

Question 8

why are electrolytes important?

Answer 8

balance water
balance acid/base (pH) level
move nutrients into cells
move wastes out of cells
make sure that nerves, muscles, the heart and the brain function

Question 9

what are all the electrolytes which are obtained through nutrition?

Answer 9

sodium, calcium, potassium, chlorine, phosphate and magnesium

Question 10

dissolved compounds dissociate into:

Answer 10

ions

Question 11

what are cations?

Answer 11

they are positively charged (move toward a negative cathode)

Question 12

give examples of cations:

Answer 12

Na+, K+, Ca2+, H+, Mg2+

Question 13

anions?

Answer 13

negatively charged (moved toward a positive anode)

Question 14

give examples of anions?

Answer 14

Cl-
HCO3-
PO43-

Question 15

non-electrolytes are…

Answer 15

uncharged

Question 16

give examples of non-electrolytes:

Answer 16

urea, glucose and amino acids (some)

Question 17

when can electrolyte levels change?

Answer 17

when the amount of water changes (dehydration or overhydration)

Question 18

causes of electrolyte levels changing:

Answer 18

drugs
vomiting
diarrhoea
sweating
renal problems

Question 19

what water disturbances can affect electrolyte levels?

Answer 19

water volume increase (oedema)
water volume decrease (dehydration)

Question 20

give examples of electrolyte disturbances:

Answer 20

hypo/hypernatraemia (disturbances in blood Na+)
hypo/hyperkalaemia (disturbances in blood K+)
hypo/hypercalcaemia (disturbances in blood Ca2+)
hypo/hyperchloraemia (disturbances in blood Cl-)

Question 21

three major compartments of the physiological fluid:

Answer 21

intracellular fluid (ICF)
interstitial fluid (part of ECF)
plasma fluid (part of ECF)

Question 22

what is intracellular fluid?

Answer 22

fluid within all the cells of the body

Question 23

what is interstitial fluid (or tissue fluid)?

Answer 23

it is a solution that bathes and surrounds the cells of multicellular animals
it is the main component of the extracellular fluid (ECF)
which also includes plasma and transcellular fluid

Question 24

what is plasma fluid?

Answer 24

main constituent of blood
separated by capillary walls
permeable to all but large proteins

Question 25

all interstitial fluid is extracellular fluid but not all extracellular fluid is interstitial fluid

Answer 25

remember

Question 26

describe intracellular fluid:

Answer 26

separated by plasma membrane permeable to water (via aquaporins) impermeable to proteins and impermeable to ions (except by specific channels and pumps)

Question 27

where does the ICF lie?

Answer 27

it lies within cells and is the principal component of the cytosol/cytoplasm

Question 28

what does the ICF make up?

Answer 28

makes up about 60% of the total body water

Question 29

what does the ECF account for?

Answer 29

for the other 40% of the total body water approx 20% of the ECF is plasma approx 75% of the ECF is interstitial fluid (ISF/IF) approx 5% of the ECF is 'other' fluid or transcellular fluid

Question 30

describe what happens to the fluid during filtration:

Answer 30

fluid exits capillary since capillary hydrostatic pressure (35mm Hg) is greater than blood colloidal osmotic pressure (25mm Hg) Arterial end net filtration pressure = +10 mm Hg

Question 31

describe what happens to the fluid when there is no net movement:

Answer 31

no net movement of fluid since capillary hydrostatic pressure (25 mmHg) = blood colloidal osmotic pressure (25 mm Hg) Mid capillary net filtration pressure = 0 mmHg

Question 32

describe what happens to the fluid during reabsorption:

Answer 32

fluid re-enters capillary since capillary hydrostatic pressure (18 mm Hg) is less than blood colloidal osmotic pressure (25 mm Hg) VENOUS END - NET FILTRATION PRESSURE = -7 mm Hg

Question 33

what are the 9 major transport systems involved in electrolyte balance?

Answer 33

Na+/K+ ATPase K+ channel Epithelial Na+ channel Voltage-dependent Na+ channel Na+ - solute co-transporter Voltage-gated Ca2+ channel Organellar Ca2+/H+ pump Plasma-membrane Ca2+/H+ pump Na2+/Ca2+ exchanger

Question 34

blood plasma has high concentrations of?

Answer 34

of sodium, chloride, bicarbonate and protein

Question 35

what does the ISF have high concentrations of and low concs of?

Answer 35

sodium, chloride and bicarbonate but a relatively lower conc of protein

Question 36

ICF has elevated amounts of?

Answer 36

of potassium, phosphate, magnesium and protein

Question 37

Describe the way the Na+/K+ pump works:

Answer 37

powered by ATP to transfer Na+ out of the cytoplasm and into the ECF The pump also transfers K+ into the cytoplasm For every ATP molecule that the pump uses, three Na+ are exported and two K+ are imported Net export of a single positive charge per pump cycle

Question 38

more positive charge is gotten rid of in order to let K+ in so a positive ion makes the inside of the cell more negative

Answer 38

remember

Question 39

describe a hypertonic solution:

Answer 39

higher solute content than ICF water moves out of cells and cells shrivel (crenated)

Question 40

describe an isotonic solution:

Answer 40

balanced solute content to ICF free movement of water in balance

Question 41

describe a hypotonic solution:

Answer 41

lower solute content than ICF water moves into cells and cells swell or lyse

Question 42

if we gave a hypertonic fluid - what would happen?

Answer 42

plasma volume expands and becomes more concentrated free movement of water and ions from plasma leads to expansion of interstitial fluid interstitial fluid becomes concentrated osmotic potential draws water out of cells cells lose water and shrink intracellular-fluid concentrated

Question 43

water movement if given a hypertonic fluid?

Answer 43

from plasma to ISF to ICF

Question 44

if we gave a isotonic fluid - what would happen?

Answer 44

plasma volume expands free movement of water and ions from plasma leads to expansion of interstitial fluid fluid is isotonic so no osmotic potential generated between ISF and cells intracellular fluid unaffected

Question 45

describe the water movement when given an isotonic fluid:

Answer 45

plasma --> ISF

Question 46

if we gave a hypotonic fluid - what would happen?

Answer 46

plasma diluted oncotic pressure reduced water moves into interstitial fluid interstitial fluid diluted osmotic potential generated between ISF and cells Water moves into cells intracellular fluid diluted cells swell

Question 47

describe the water movement when given a hypotonic fluid:

Answer 47

water movement from plasma --> ISF --> ICF

Question 48

what is crystalloid fluid?

Answer 48

contains small solutes, mineral salts

Question 49

what is colloid fluid?

Answer 49

contains large solutes

Question 50

why would you give crystalloid to clinical case on slide 24?

Answer 50

need to replace lost water and lost electrolytes

Question 51

why and when might you give a colloid?

Answer 51

blood pressure low and circulation is poor low circulating volume - so give colloid to increase blood pressure

Question 52

why give isotonic for clincial case slide 24?

Answer 52

to replace lost fluid and solutes without overloading ICF with fluid (hypotonic) or drawing fluid form ICF (hypertonic)

Question 53

when may you give hypotonic?

Answer 53

hypotonic not very useful clinically as rarely have fluid loss without electrolyte loss as well

Question 54

when may you give hypertonic?

Answer 54

hypertonic can function like colloid but only short-term as fluid will be lost from ICF as a result animal can replace ICF with long term drinking so sometimes used in large animals

Question 55

what routes could you give fluids?

Answer 55

orally, subcutaneous, IV

Question 56

how to calculate how much fluid to give:

Answer 56

calculate fluid deficit, calculate maintenance requirements and add together determine safe rate to administer (this will be covered in later years) like w/ like volume w/ volume rate w/ rate

Question 57

osmosis occurs through?

Answer 57

through semi-permeable membrane

Question 58

cell membrane acts as a ?

Answer 58

a barrier to most molecules

Question 59

why are the cell membranes semi-permeable?

Answer 59

specialised channels and transporters facilitate movement across the membrane

Question 60

how does water move across membranes?

Answer 60

lipid bilayer is hydrophobic - therefore, only gases and molecules such as ethanol can diffuse across only limited diffusion of water occurs too slow for most physiological processes

Question 61

water crosses the plasma membrane via?

Answer 61

its own channels - aquaporins

Question 62

three hormone systems play an important role in the regulation of extracellular fluid volume and osmolarity through their actions on renal absorption of Na+ and water - what are they?

Answer 62

ADH (anti-diuretic hormone) the renin-angiotensin-aldosterone system atrial natriuretic hormone

Question 63

which two fluid compartments have the most similar compositions of fluid?

Answer 63

the compositions of the two components of the ECF - plasma and ISF - are more similar to each other than either is to the ICF