I would like some ideas on two organ systems and how the two together keep the human body functioning as a unit

Answer 1

One example is how the muscular and respiratory systems work together. If the muscles become weak or paralyzed, as may happen in ALS disease, then the lungs may not work well. We need muscles to keep inflating and deflating the lungs.

For more examples, check these sites.

http://web.jjay.cuny.edu/~acarpi/NSC/14-anatomy.htm

http://www.daviddarling.info/encyclopedia/O/organ_system.html