Fluid balance

Question 1

Extracellular fluid consists of…

Answer 1

Interstitial fluid
Blood plasma
Transcellular fluid

Question 2

Interstitial fluid is formed by…

Answer 2

More fluid being pushed out in capillary beds than is being drawn back in

Question 3

What are the main ions in ECF?

Answer 3

Na, Cl and HCO3-

Question 4

What are the main ions in ICF?

Answer 4

K+, Mg, Protein

Question 5

What is a mole?

Answer 5

an amount of substance that contains the number of molecules equal to Avogadro’s number (6 x 10 to the 23).

Question 6

Define concentration

Answer 6

a measure of how much of a given solute is dissolved in a given volume of solvent : Usually moles per litre(dm3)

Question 7

What is the difference between molarity and molality?

Answer 7

Molarity = number of moles per litre (use a M eg. 5M)

Molality = number of moles per kg of solvent (Use m eg. 5m)

Question 8

One milliequivalent is equal to how many moles?

Answer 8

1 milieq = 10(-3) eq

so 1 meq = 1mmol

Question 9

What is the water potential?

Answer 9

The tendency of the water molecules to move out of a solution is known as the water potential, Ψ.

Question 10

How does water move with regard to water potentials?

Answer 10

Water always moves from a region of higher water potential to a region of lower water potential.

Question 11

What is the water potential of pure water?

Answer 11

In pure water, the water potential is 0

Question 12

What is the osmotic pressure?

Answer 12

This is the pressure, exerted by the solute particles in the solution, which prevents the movement of water across a membrane
Equivalent to the osmotic potential or Ψs

Question 13

What are colloids?

Answer 13

Colloids are large molecular weight particles present in solution

Question 14

What is oncotic pressure?

Answer 14

Oncotic pressure is the proportion of the total osmotic pressure in plasma exerted by colloids

Question 15

What is the effect of hypertonic solution on cells?

Answer 15

Cells shrivel up and are plasmolyzed

Question 16

What is the effect of hypotonic solution on cells?

Answer 16

Cells swell as they take on water and can lyse

Question 17

What is an osmole?

Answer 17

Osmole = The number of ions or particles into which a solute dissociates in solution.
eg 1 mole of NaCl –> Na and Cl so is 2 osmoles

Question 18

What is the difference between osmolality and osmolarity?

Answer 18

Osmolality is the number of osmoles of solute per kg solvent (temp independent)
Osmolarity is the number of osmoles per litre of solution

Question 19

What is tonicity?

Answer 19

Tonicity is the effective osmolality and is equal to the sum of the concentration of the solutes which have the capacity to exert an osmotic force across the membrane.

Question 20

What is the osmolality of serum and ECF in dogs?

Answer 20

300mOsm/kg

Question 21

In hypotonic fluid loss what happens to ECF?

Answer 21

As the ECF is hypertonic the ECF Increases preserving circulating fluid volume

Question 22

What is the effect of IV Isotonic crystalline fluid?

Answer 22

Plasma volume: Expanded proportionally to its volume of the ECF
ISF: Expanded
ICV: unchanged

Question 23

What is the effect of IV Hypertonic crystalline fluid?

Answer 23

ISF increases so PV increases but ICV decreases

Question 24

What is the effect of IV colloid fluid?

Answer 24

PV increases
ISF remains unchanged
ICV remains unchanged

Question 25

What effect does slow change to ECF tonicity have on ICF?

Answer 25

No effect as Extracellular hypertonicity increases expression of genes encoding proteins that increase intracellular osmoles