Physiology - Osmolality

Question 1

What is osmolarity?

Answer 1

Concentration of osmotically active particles present in a solution

Question 2

How is osmolarity calculated?

Answer 2

Molar concentration x no. of osmotically active particles

Question 3

Are osmolarity and osmolality the same thing?

Answer 3

Yes - just difference in units used

Question 4

What is tonicity?
What do the following terms mean:
- isotonic
- hypotonic
- hypertonic

Answer 4

Effect a solution has on cell volume

Isotonic - no difference
Hypotonic - increase in cell volume
Hypertonic - decrease in cell volume

Question 5

Match the following tracers (markers) to their body fluid component:

Inulin
Tritiated H2O
Labelled albumin

TBW
Plasma
ECF

Why are tracers clinically significant?

Answer 5

ECF = inulin 
TBW = tritiated water
Plasma = labelled albumin 

They allow you to work out an unknown volume using calculations

Question 6

Is Na+ higher or lower in ICF or ECF?

Same question for Cl- and K+

Answer 6

Na+ - high in ECF

Cl- - high in ECF

K+ - high in ICF

Question 7

The osmolarity of ICF and ECF are v different. T/F?

Answer 7

F - they are almost exactly the same ~300mosmol/l