Salt and water balance
-Osmolality is a count of the number of particles present in solution and is
independent of sieze or weight of the particles
-Isosmotic refers to solutions that have the same number of dissolved
particles/kg of water
e.g. 3000mmol of glucose = 300mmol of urea = 150mmol of NaCl
Tonicity is the effective
Hypotonic solution = cell lyses
Isotonic = normal cell
Hypertonic solution = cell shrivles
Colloid osmotic pressure = just proteins
Total osmotic pressure = proteins and all osmotically active particles e.g. salts
300mosmooles/kg in 42kg body water
total no. of osmoles in 42kg H2O
= 300x42 = 12600mOsm
If drinking 700ml H2O then expanding body water by 700g, total body water is
now 42.7Kg
Now have 12600mOsm in 42.7Kg of H2O, i.e. 12600/42.7 = 295.1 mosmoles/Kg
If you drink wter, plasma volume will increase and you will dilute the plasma
proteins.
This will increase volume of ISF and also dilute it. Therefore it will be more dilute
than ICF and water will move in.
If you drink isotonic water, you will increase hydrostatic pressure slightly but
not change tonicity.
So you will have movement out of the plasma into ISF, but not into cell, as it is
the same tonicity.
For a man, we would give intravenously a glucose isotontonic solution. This gives
gentle movement of water into cells?
(iv) RAAS and ANP system
(v)
-Osmolality is a count of the number of particles present in solution and is
independent of sieze or weight of the particles
-Isosmotic refers to solutions that have the same number of dissolved
particles/kg of water
e.g. 3000mmol of glucose = 300mmol of urea = 150mmol of NaCl
Tonicity is the effective
Hypotonic solution = cell lyses
Isotonic = normal cell
Hypertonic solution = cell shrivles
Colloid osmotic pressure = just proteins
Total osmotic pressure = proteins and all osmotically active particles e.g. salts
300mosmooles/kg in 42kg body water
total no. of osmoles in 42kg H2O
= 300x42 = 12600mOsm
If drinking 700ml H2O then expanding body water by 700g, total body water is
now 42.7Kg
Now have 12600mOsm in 42.7Kg of H2O, i.e. 12600/42.7 = 295.1 mosmoles/Kg
If you drink wter, plasma volume will increase and you will dilute the plasma
proteins.
This will increase volume of ISF and also dilute it. Therefore it will be more dilute
than ICF and water will move in.
If you drink isotonic water, you will increase hydrostatic pressure slightly but
not change tonicity.
So you will have movement out of the plasma into ISF, but not into cell, as it is
the same tonicity.
For a man, we would give intravenously a glucose isotontonic solution. This gives
gentle movement of water into cells?
(iv) RAAS and ANP system
(v)
