homeostasis 2 Flashcards
how is water balance maintained?
thirst mechanism kidney function( urinary loss) sweating is a short term solution
where is water in the body
Intercellular water
extracellular water = plasma + interstitial
what can pass through the capillary wall
everything except plasma proteins.
how does water move through the body
freely. it is controlled by osmosis
how are the plasma and the ISF different
they are very similar. the ISF does not contain plasma proteins
how is water distributed in the body
1/3 body water is in the ECF. 2/3 in the ICF.
The ICF has double the fluid compared to the ECF
How is water distributed in the ECF
80% in ISF. 20% in plasma
What does water body content depend on?
age and sex.
More water is contained in muscles ( 70%) than fat ( 10%). Men have more muscle than women. Older generations have less muscle than younger ones.
how does water content affect drug administration
lipid soluble drugs will last longer in Bodies with higher fat content.
water soluble drugs will last longer in higher water body content.
dilution principle
V= m/ C
substances which stay in one compartment of the blood and what do they allow to calculate
1-plasma proteins- plasma volume
2-molecules which are to large to pass through cell wall or ions which are forced out of cells e.g. sodium and cl e.g. sucrose, insulin- ECF volume
3-heavy water -TBW
how to measure body fluids?
1-administer drug into one compartment of the body and wait for it to distribute
2- calculate how much has been metabolised/excreted
3- measure the volume of distribution:
amount injected ( - amount lost)/conc of sampled fluid
how to calculate ICF and ISF
ICF= TBW -ECF
ISF=ECF-PV
why is the difference in concentration of ions between. the ICF and the ECF so important
It maintains a concentration gradient which is essential for action potential transmission.
What does total sodium content control?
the volume of the ECF
