Week 1 (minus anatomy) Flashcards
(35 cards)
What is osmolarity?
The concentration of osmotically active particles in a solution.
What is osmolarity measured in?
osmol/l or mosmol/l
Which two factors need to be known for osmolarity to be calculated?
The amount of osmotically active particles present
The molar concentration of a solution.
Calculate the osmolarity of 150nM of NaCL
NaCl is two osmotically active particles.
Therefore 150 x2 = 300osmol/l
Calculate the osmolarity of 100nM of MgCl(2)
3 x 100 =300osmol/l
What is the difference between osmolarity and osmolality?
Osmolality has the units osmol/kg of water. However the two are interchangeable at concentrations of weak solutions (like bodily fluids).
What is a hypertonic solution?
It gives away water.
What is a hypotonic solution?
It takes in water
What is a isotonic solution?
Net movement of water is equal.
How is the total body water divided up?
33% extracellular fluid
67% intracellular fluid
What makes up extracellular fluid?
Plasma volume
Interstitial fluid
Lymph
How would you go about measuring different compartments?
Specific tracers can measure different body compartment volumes.
Insulin can measure extracellular volume
Labelled albumin can measure plasma
Tritilated water measures total body volume
How would you work out intercellular volume using tracers?
Total body vol= intracellular plus extracellular.
Using tracers you can find out TBV and EC therefore you can work out IC.
How would you use the dilution principle to work out volume of distribution?
You could put a known volume of tracer (42mg) in an unknown volume of liquid.
Mix it around for it to reach equilibrium
Then extract a 5ml sample. Work out the concentration of the tracer in this volume. Example tracer concentration = 0.005mg/5ml therefore 0.001/ml therefore 1mg/l of tracer.
Then using V (litres)= Dose/sample conc
You can work out 42/1mg/l = 42 litres. (uses volume = mass/concentration)
What is insensible water loss?
Water lost that can’t be helped. Not by sweating or anything but simple diffusion into the environment or lost in breath.
What is sensible water loss?
Sweat- depends on the activity we are doing
Faeces water loss
Lost in urine.
Why can’t the kidneys maintain water balance?
The kidneys need to produce urine to excrete certain waste products that can’t be excreted any other way. So they can compensate for water loss to a certain extent by lowering urine production but they can’t completely stop it.
Describe the distribution of Na, K, Cl, and HCO3 intracellularly and extracellularly.
ICF- ECF
Na. 10 140
K 140 4
Cl 7 115
HCO3 10 28
What would happen if solute concentration (osmolarity concentration) increased extracellularly?
Water would move out of the cell to try and maintain a constant concentration.
What would happen if solute concentration (osmolarity concentration) decreased extracellularly?
Water would move into the cell to try and balance the concentrations.
Name the three challenges to fluid homeostasis in the body
Gain or loss of NaCl
Gain or loss of isotonic solution
Gain or loss of water.
Why is sodium so important in balance of fluid in the body?
90% of the osmotic concentration of the ECF results from the presence of sodium.
Major determinant of ECF volume.
What affect can fluctuations in potassium cause?
It can have a detrimental affect on muscle function and cardiac function due to it being key in establishing membrane potential.
Loss of potassium leads to muscle weakness which can result in paralysis
And cardiac abnormalities which can lead to cardiac arrest.
What level is the right renal hilum at?
L1/L2
