K1 - Body Fluid Compartments and Challenges to Homeostasis

Question 1

what is osmolarity ?

Answer 1

concentration in a solution of osmotically active particles

Question 2

How can osmolarity be calculated?

Answer 2

molar concentration x number of osmotically active particles

Question 3

what is the difference between osmolarity and osmolality?

Answer 3

osmolality is measures in osmole per kg or water where as osmolarity is meausres in osmole per litre of water

Question 4

what is tonicity?

Answer 4

the effect a solution has on the volume of a cell

Question 5

what is a solution called when there is no change in cell volume?

Answer 5

isotonic

Question 6

what happens if a solution is hypotonic?

Answer 6

increase in cell volume

Question 7

what happens if a solution is hypertonic ?

Answer 7

decrease in cell volume

Question 8

what are the body fluid compartments ?

Answer 8

intracellular fluid - 67%

extracellular fluid -33%

Question 9

what does the extracellular fluid contain?

Answer 9

plasma - ~20%
interstitial fluid - 80%
lymph and transcellular fluid (negligible)

Question 10

what can be used to meausure volumes in the body fluid compartments?

Answer 10

tracers - specific chemicals which can be used to determinate the distribution volume

Question 11

examples of tracers

Answer 11

TBW - 3H2O
ECF - inulin
Plasma - labelled albumin

Question 12

what is the equation used to measure the volume of distribution?

Answer 12

Volume = Dose/ Sample Concentration

Question 13

how is water balance controlled in our body?

Answer 13

homeostasis where water input = water output

Question 14

what causes water imbalance?

Answer 14

changes in body fluid osmolarity

Question 15

what are ways in which water is taken in ?

Answer 15

fluid intake
food intake
metabolism

Question 16

what are ways in which water is outputted?

Answer 16

insensible loss - skin & lungs

sensible loss - sweat, faeces and urine

Question 17

what are the general values of ionic composition of major fluid compartments?

Answer 17

more Na+ and Cl- outside the cell

more K+ inside

Question 18

what is important about the osmolarity of the extra/intracellular fluids?

Answer 18

they are the same

Question 19

what is fluid shift ?

Answer 19

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

Question 20

what happens when he osmotic concentration o ECF increases?

Answer 20

• occurs when dehydrated
• took away water left the salt so ECF is hypertonic compared to the cell
• less water outside the cell so water will move from inside to outside so cell volume would decrease and the ECF would increase

Question 21

what happens when the osmotic concentration of the ECF decreases?

Answer 21

• caused by over hydration

- more water in ECF than ICF so water move into cell resulting in increase cell volume and decreases ICF

Question 22

what happens i there is a gain or loss of water?

Answer 22

change in fluid osmolarity so similar changes in ICF and ECF

Question 23

what happens when there is a gain or loss of NaCl ?

Answer 23

change in fluid osmolarity resulting in Na+ excluded from ICF and osmotic water movements

Question 24

how does ICF and ECF volumes change with a loos or gain of NaCl?

Answer 24

gain - increase ECF decrease ICF

loss - decrease ECF and increase ICF

Question 25

what happens if there is a gain or loss of isotonic fluid ?

Answer 25

no change in fluid osmolarity only change in ECF volume

Question 26

when does electrolyte balance occur?

Answer 26

rate of gain = rate of loss

Question 27

why is electrolyte balance important?

Answer 27

• total electrolyte concentration can directly affect water balance
• the concentrations of individual electrolytes can affect cell functions

Question 28

why are K|+ and Na+ important in electrolyte balance?

Answer 28

• major contributors to the osmotic concentrations of EFC and ICF
• directly affect the function of all cells