The Basic Principles of Fluid Balance

Question 1

• What makes up your ECF?

Answer 1

ISF, plasma volume & transcellular fluid

Question 2

• What is the difference between molarity and molality?

Answer 2

Molarity is the number of moles per litre

Molality is the number of moles per kg of solvent

Question 3

• What is an osmole?

Answer 3

The number of ions or particles into which a solute dissociates in solution (e.g. 1M NaCl = 2 osmoles)

Question 4

• What is the water potential of pure water?

Answer 4

Zero

Question 5

• What is colloid osmotic pressure?

Answer 5

The osmotic pressure exerted by plasma colloids

Question 6

• What is tonicity?

Answer 6

The effective osmolality of a solution i.e. the osmotic pressure of a fluid when compared with plasma

Question 7

• How do changes in ECF tonicity effect ICF volume?

Answer 7

Rapid changes in ECF tonicity alter cell volume, slow and moderate changes in ECF tonicity have no effect on ICF volume