Problem Set 3: Body Fluids Exam Questions And Answers

True/False: A normal lean person consists of ~ 95% water. - ANS False, ~ 60% water. True/False: Most of the sodium in the body is inside the cells. - ANS False; It is extracellular. True/False: The capillary is the main barrier between the intracellular and extracellular fluids. - ANS False; The cell wall (plasma membrane separates intracellular and extracellular fluid. The capillary separates the interstitium and the plasma, both sub- compartments of the extracellular fluid. True/False: To measure the volume of the entire extracellular fluid compartment, we use a substance that moves freely across the capillary but cannot enter the cell. - ANS True; An example is inulin. True/False: Water and small solutes move across the capillary wall by active transport. - ANS False: All movement across the capillary wall is passive, driven by hydrostatic and colloid osmotic (oncotic) pressures. True/False: The osmolality of the body fluids is greater when all the solutes are large. - ANS False: The total number of particles, irrespective of size, determines osmolality. True/False: All water movement in and out of cell is passive. - ANS True; water movement is driven by solute (osmotic) gradients across the cell wall. True/False: Sodium (Na) is effectively impermeable at the cell wall. - ANS True: Any Na that does enter the cell will be immediately removed by the Sodium potassium ATPase in the cell wall. True/False: Eating a meal high in salt, without drinking any water will lead to an increase in both intracellular and extracellular fluid volume. - ANS False: This is a Hypertonic expansion: Ingest NaCl stays extracellular, increases the ECF osmolality, H2O moves OUT of cells to restore osmotic equilibrium. Decrease in ICFV, increase in ECFV. True/False: A pure water solution can safely be infused intravenously to a dehydrated person. - ANS False: Water will enter the surrounding cells causing swelling and lysis. The potassium released in to the extracellular fluid by cell lysis can be fatal. A 5% glucose solution is iso-osmotic to body fluids, so safe to infuse. After metabolism of the glucose this is equivalent to giving pure water.