HSF 4 - Unit 1 Physiology: Body Fluid Compartments

Question 1

what is TBW composed of? what is the estimated value?

Answer 1

TBW = ICF + ECF; 42 L

Question 2

what is ECF composed of? what is the estimated value of each component and the total?

Answer 2

ECF = ICF + Plasma
ECF is about 14 L
IF is about 11 L
Plasma is about 3 L

Question 3

what is the estimated value of the ICF?

Answer 3

28 L

Question 4

what is the osmolarity of the body fluid compartments?

Answer 4

all are 300 mOsm

Question 5

what electrolytes and molecules are higher in the ICF? which is the most important for determining the environment of this fluid?

Answer 5

high in K+, Mg2+, proteins, HPO4; K+ is most important determiner of tonicity and volume

Question 6

what electrolytes and molecules are higher in the ECF? which is the most important for determining the environment of this fluid?

Answer 6

high in Na+, Ca2+, Cl-, HCO3-; Na is most important determiner of tonicity and volume

Question 7

what is the difference between the plasma and IF? why is this significant and what effect is working here?

Answer 7

plasma is higher in proteins, which are negatively charged, thus causing charged particles to distribute unevenly across plasma and IF, with more cations attracted to the plasma and anions repelled into the IF; Gibbs-Donnan effect

Question 8

what 2 mechanisms are used to maintain homeostasis? what 2 kinds of components are important to homeostasis?

Answer 8

across cell membranes by osmotic forces (based on concentrations) and across capillaries by hydrostatic (outward circulatory) and colloid osmotic forces (inward circulatory; oncotic); have to maintain volume and concentration

Question 9

where do most volume disturbances originate?

Answer 9

ECF

Question 10

what can happen if the kidneys are unable to maintain the ECF volume?

Answer 10

hypervolemia and edema (CHF risk) or hypovolemia and reduced organ perfusion (death)

Question 11

what is the 60-40-20 principle?

Answer 11

TBW = 60% * body weight in kg
ICF = 40% * body weight in kg (also 67% of TBW)
ECF = 20% * body weigght in kg (also 33% of TBW)

Question 12

what radioactive markers are used for TBW?

Answer 12

radioactively labeled H2O and antipyrine

Question 13

what radioactive markers are used for ECF?

Answer 13

22Na, Inulin, Mannitol

Question 14

how can we determine ICF?

Answer 14

TBW - ECF

Question 15

how can we determine IF?

Answer 15

ECF - Plasma (3/4 of ECF, about 10.5L)

Question 16

how can we determine plasma?

Answer 16

125I-albumin or Evans blue markers (1/4 of ECF, about 3.5L)

Question 17

how can we determine total blood volume?

Answer 17

plasma volume / (1-Hct)

Question 18

which compartments do not have indicators?

Answer 18

ICF, IF, total blood volume

Question 19

what are factors that influence TBW estimates? how can we correct for these mathematically?

Answer 19

fat (10% fluid per kg of fat, can use the 60% for other lean kg mass)
age (70% for babies and 50% for elderly)
gender (60% for males and 55% for females); should use 67% and 33% values to individually calculate IF and Plasma of the ECF to avoid overestimations

Question 20

what is the indicator dilution principle?

Answer 20

volume = (injected - excreted) / concentration measured

Question 21

what are the 3 steps to determine the Darrow-Yannet diagram of a scenario?

Answer 21

Step 1.What happens to thevolume in theECF compartment(ECF is the smaller compartment)?
Step 2. What happens to thein themOsm of the ECF compartment(ECF is the smaller compartment)
Step 3. What happens to the volume and osmolality of the ICF?

Question 22

what happens hormonally if you increase blood osmolarity?

Answer 22

AVP/ADH released from the posterior pituitary, causing mainly reabsorption of water from the renal collecting ducts
*hypotonic reabsorption

Question 23

what happens if you lose plasma volume?

Answer 23

RAAS is released, causing Na+ reabsorption in the renal tubules, thus causing more water reabsorption since it follows Na+

Question 24

what are the effects of hyponatremia?

Answer 24

induction of diffusion of H2O into the brain cells, lowering brain osmolarity and swelling of the brain, which induces the transport of Na, K, and organic solutes out of the cells which will cause water to diffuse out of the cells to combat the hypertonicity (causes increased expression of genes encoding proteins that increase intracellular osmoles like myoinositiol, glu, gln, and sorbital) of the extracellular environment. Therapy slowly allows adequate time for replacement of organic osmolytes to occur in the neural tissues, but demyelination occurs with improper therapy (too rapid) because of direct injury to astrocytes/oligodendrocytes that are needed for myelination and remyelination.