Physiology 1 Flashcards
Tracer for TBW
3H20
Tracer for ECF
Inulin
Tracer for plasma
Labelled albumin
V=D/C
Volume (litres) = Dose/Sample concentration
How do you measure water imbalance?
Changes in body fluid osmolarity
Sodium greatest concenctration ICF or ECF?
ECF
-lots of chlorine in ECF as well
(potassium in ICF)
Fluid shift?
Movement of water between the ICF and ECF in response to an osmotic gradient
Gain and loss of NaCl and change in volumes of ECF and ICF
ECF NaCl gain:
ECF ↑ ICF↓
ECF NaCl loss:
ECF ↓ ICF ↑
What happens with gain or loss of isotonic fluid?
e.g. 0.9% NaCl solution
= no change in fluid osmolarity
Change in ECF only
Primary anion of the ECF?
Chlorine
Primary cation of the ECF?
Sodium
cation = positive
When does electrolyte balance occur?
When rates of gain = rates of loss (lol)
> 90% of the osmotic concentration of the ECF results from the presence of …?
sodium salts
What can happen if concentration of K+ falls?
Muscle weakness –> paralysis
Cardiac irregularities –> cardiac arrest
Plays a key role in establishing membrane potentials?
K+
Salt imbalance is manifested as changes in …?
Salt imbalance is manifested as changes in extracellular fluid volume
(remember water was measured as changes in osmolarity)
ICF percentage of TBW?
67%
ECF percentage of TBW?
33%
plasma makes 20% of this, Interstitial fluid makes 80% of this
Main ions in the ECF?
Na+, Cl-, HCO3
Main ions in the ICF?
K+, Mg2+
Which ion is mainly present in the ECF and is therefore a major determinant of ECF volume?
Na+
You need to control this ion to prevent muscle weakness (–> paralysis) and cardiac irregularities (–> cardiac arrest)
K+
Regulation of what is important for the long-term regulation of blood pressure?
Extracellular fluid volume
Total body water of male?
60% of body weight
