In order for students to gain a deeper understanding of homeostasis in the human body, groups will design their own experiment (with parameters) to test how internal conditions remain stable as external conditions change. 

In each of these experiments, you can use whatever resource you would like for your lab set up.  The following are general outlines for each: 

Temperature Investigation: 

Test subject should submerge hand in ice water (no longer than 30 seconds).  Two temperature probes are required, one taped to the hand that is in ice water (make sure to cover with tape as much as possible so that the probe is recording temperature of skin rather than water), and one in the crook of the elbow of the same hand (this represents core). Temperature recordings should be taken continuously over time (preferably 5 minutes or longer) to show the body attempting to recover surface temperature and maintain core.

Pulse/Breathing Rate: 

Students can pick whatever exercise they want to do for this investigation, but make sure they are very clear on how to record pulse & breathing rate (read for 30 sec intervals and multiply by 2).  Again, the readings should take place for up to 5 minutes (preferably longer) after the exercise to show the systems returning to stability.  

pH:

Various homogenates can stand in for the living system - a potato "smoothie", a liver "smoothie," even whole milk should work.  The general set up is 2 test cups (less than 25 mL each) of homogenate and 2 test cups of distilled water.  2 members can test the effect of 1.0M HCl and 2 members can test 1.0M NaOH.  Acid/base is added 5 drops at a time to homogenate/water and pH is tested after each addition of drops (30-35 drops total).  Again, more is better, but 30-35 drops should be enough to show the change in water and the relative stability of living system.  NOTE: remind students to "swirl" after adding drops and not to insert pH strip/meter in the same place as drops were added.  The homogenates sometimes separate out into water and living cells, so make sure they are stirring to maintain a fairly consistent mix.