Body fluid compartments and challenges to homeostasis Flashcards
what is osmolarity?
The concentration in a solution of osmotically activated particles
What 2 factors do you need to calculate osmolarity?
Molar concentration of solution and number of osmostically active particles
what is the difference between osmolarity and osmolatity?
-Osmolatity units are ormolu by kg of water instead of mosmol/l
What is tonicity?
the effect a solution has on the volume of a cell
What 3 types of tonicity can a solution have?
Isotonic – no impact on cell volume
Hypotonic- increase in cell volume
Hypertonic- decrease in cell volume
what can a hypotonic solution result in?
Cell lysis
Why do females have less total body water weight?
more adipose tissue and fat cells have very little water
What are the two major components of total body water?
Intracellular fluid (67%) and extracellular fluid (33%)
what does the extracellular fluid include?
Plasma (~20% of ECF)
Interstitial fluid (~80% of ECF)
Lymph (negligible) + Transcellular fluid (negligible)
What can be used to measure these fluids?
Tracers - specific chemicals that can be used to determine the distribution volume
Name some useful tracers?
TBW: 3H2O
ECF: Inulin
Plasma: labelled albumin
what is the equation for working out the volume using a tracer?
V(litres)= Dose (D)/ sample conc (C)
what is homeostasis?
Maintaining a stable internal environment
How is homeostasis achieved?
input(s) = output (s)
What is insensible loss?
loss of water over that we have no physiological control of body i.e diffusion of water across the surface of our skin
What is sensible loss?
Output of water that we have some control over i.e sweat / urine
During hot weather or prolonged heavy exercise , how is water balance maintained?
Water balance is maintained by increased water ingestion. Decreased excretion of water by the kidneys alone is insufficient to maintain water balance
where is there always a higher concentration sodium and chloride ions?
extracellular fluid
where is there always higher concentration of potassium ions?
intracellular fluid
what is plasma and interstitial fluid separated with?
capillary wall
what is interstitial fluid and intracellular fluid separated by?
plasma membrane
What allows cells to maintain internal environments that differ in composition compared to their surroundings?
cell membrane and membrane transport mechanisms
how do osmotic concentrations of ECF and ICF differ and why?
- osmotic concentrations are identical
- Because changes in solute concentrations lead to immediate changes in water distribution, the regulation of fluid balance and electrolyte balance are tightly intertwined
what is fluid shift?
Movement of water between the ICF and ECF in response to an osmotic gradient
What happens if osmotic concentration of the ECF increase because of dehydration?
Lost more water than you should, salt concentration of extracellular fluid increased, extracellular fluid is hypertonic compared to inside the cell , water move out cell to ECF to restore osmotic equilbirum
what happens if osmotic concentration of the ECF decreases because of overhydration?
Added more water to ECF, more water outside the cell than inside , water moves in and increases cell volume
what are the 3 challenge to fluid homeostasis?
- gain or loss of water
- gain or loss of NaCl
- gain or loss of isotonic fluid
what causes the gain or loss of NaCl?
Na+ “excluded” from ICF (recall ion distributions)
(b) Osmotic water movements
These two factors combine to produce opposite changes in ICF and ECF volumes
what alters composition and volume of ECF?
kidneys
why Is regulation of ECF volume vital?
Vital for long term regulation of blood pressure
How is electrolyte balance maintained?
when rates of gain = rates of loss
why is electrolyte balance important?
1) Total electrolyte concentrations can directly affect water balance
2) The concentrations of individual electrolytes can affect cell functions
why are Na+ and K+ important?
a) They are major contributors to the osmotic concentrations of the ECF and ICF, respectively
b) They directly affect the functioning of all cells
what does the presence of sodium salts result to?
90% of the osmotic concentration of the ECF
what plays a key role in establishing membrane potential ?
K+
small leakages or uptake may severally affect K+ plasma leading to what ?
- muscle weakness - paralysis
- cardiac irregularities- cardiac arrest
what is salt imbalance a result of?
Changes in extracellular fluid volume
