Physiology - Body Fluid Compartments

Question 1

what is osmolarity?

Answer 1

the concentration of osmotically active particles in a solution

mosmol/l

Question 2

how do you calculate osmolarity?

Answer 2

molar concentration of a solution x the number of osmotically active particles in the solution

Question 3

what are the units of osmolality?

Answer 3

osmol/kg of water

Question 4

what is the osmolarity of body fluids?

Answer 4

around 300 mosmol/l

Question 5

what is tonicity?

Answer 5

the effect a solution has on cell volume

Question 6

what are the three tonicities a solution can have?

Answer 6

hypotonic
hypertonic
isotonic

Question 7

what does hypotonic mean?

Answer 7

causes the cell to swell

Question 8

what does hypertonic mean?

Answer 8

causes the cell to shrink

Question 9

what does isotonic mean?

Answer 9

has no effect on cell volume

Question 10

what two compartments make up TBW?

Answer 10

ICF (66%)

ECF (33%)

Question 11

what is ECF made of?

Answer 11

plasma
interstitial fluid
lymph
transcellular fluid

Question 12

how can body fluid compartments volumes be measured?

Answer 12

using tracers

obtain their volume of distribution

Question 13

what tracer is used to measure TBW volume?

Answer 13

3H2O

Question 14

what tracer is used to measure ECF volume?

Answer 14

inulin

Question 15

what tracer is used to measure plasma volume?

Answer 15

labelled albumin

Question 16

what is the equation for measuring the volume of distribution of a tracer?

Answer 16

V = dose of tracer (D)/sample concentration (C)

Question 17

what does water imbalance cause?

Answer 17

fluid shifts between the ICF and ECF by osmosis

Question 18

what are the main ions in the ICF?

Answer 18

potassium

Question 19

what are the main ions in the ECF?

Answer 19

sodium
chloride
bicarbonate

Question 20

what separates interstitial fluid from the intracellular fluid?

Answer 20

plasma membranes

Question 21

what separates plasma from the interstitial fluid?

Answer 21

the wall of the vasculature

Question 22

what is the major determinant of plasma osmolarity?

Answer 22

sodium

Question 23

how can you estimate plasma osmolarity?

Answer 23

double the plasma sodium ion concentration

Question 24

what are the osmolarities of the ECF and ICF?

Answer 24

botha round 300 mosmol/l

Question 25

what is a fluid shift?

Answer 25

the movement of water between the ICF and the ECF in response to an osmotic gradient

Question 26

what happens when there is a gain/loss of water?

Answer 26

ICF and ECF volumes change

Question 27

what happens to the ECF and ICF volumes if the ECF gains NaCl?

Answer 27

ECF increases

ICF decreases

Question 28

what happens to the ECF and ICF volumes if the ECF loses NaCl?

Answer 28

ECF decreases

ICF increases

Question 29

what happens if an isotonic fluid is gained or lost?

Answer 29

change occurs in the ECF fluid volume only

Question 30

what organ controls the composition and volume of the ECF?

Answer 30

the kidneys

Question 31

what is an electrolyte?

Answer 31

any substance that dissociates into free ions when dissolved

e.g. NaCl

Question 32

how is most sodium input achieved?

Answer 32

through the diet

Question 33

how is most sodium output achieved?

Answer 33

urine