Body Fluid Compartments Review

Flashcards about body fluid compartments, osmolality, and fluid shifts between ICF and ECF. Focuses on permeability, volume expansion/contraction types, and clinical scenarios.

What determines the osmolality of body fluids?

The presence of solutes and the number of free, dissociated particles in solution.

Why is osmotic equilibrium possible between ICF and ECF?

The cell membrane is freely permeable to water, allowing water to move passively.

What is the reflection coefficient of NaCl and what does it imply?

It is 1.0, indicating NaCl is impermeable and generates sustained osmotic effect.

What happens when iso-osmotic glucose is infused?

Glucose is taken up by cells, water follows, and glucose is incorporated into other molecules, effectively being equivalent to infusing pure water.

What happens when urea is introduced to a cell?

Urea diffuses into the cell, takes water, which causes the cell to swell, but there is no change in cell osmolality.

What happens during hypotonic expansion and give an example?

Both ECF and ICF expand, osmolality falls, and TB H2O increases, causing cell swelling. An example is drinking water.

What happens during isotonic expansion and give an example?

Only ECF expands and there is no change in osmolality. TB H2O increases, leading to edema. An example is infusion of 0.9% NaCl.

What happens during hypertonic expansion and give an example?

ECF osmolality increases, H2O moves out of cells, ICFV decreases, ECFV increases, osmolality increases, and TB H2O does not change. An example is ingesting NaCl without water.

What happens during hypertonic contraction?

Both ECF and ICF volumes decrease.

What happens during isotonic contraction?

ECF decreases which can lead to cardiovascular collapse.

What happens during hypotonic contraction?

There is a fall in ECF volume and an increase in ICF volume, leading to cell swelling.

What happens to the ECF volume and osmolality of someone lost in the desert who is sweating profusely?

ECFV will fall (volume loss) and ECF osmolality will rise (more water than salt loss).

Why can't you infuse pure water intravenously?

It will cause cells to swell and burst, releasing K+ into the plasma and leading to hyperkalemia, which can cause spastic paralysis.

What IV solution can be administered that is like water but will not cause cell lysis?

5% glucose solution (osmolality = 300 mosm/L).

What is the overall conclusion of the body fluid lectures?

In the short term, fluid is moved between compartments to maintain equilibrium. In the long term, the kidneys maintain constant volume and composition of body fluids.