Have your ever hiked down into the Grand Canyon? Why do you think it would be important to bring not just plenty of water, but food as well?
Discuss the condition hyponatremia, what causes it? Which electrolytes are particularly involved in fluid balance? Which are intracellular vs extracellular? Why would loss of electrolytes affect osmotic gradients in your brain (resulting in coma!). Would your brain cells be hypertonic, hypotonic or isotonic to surrounding fluid?