There are a lot of things going on in the human body that no one thinks about until they go awry. This is thanks to homeostasis (from the Greek homeo, meaning "similar," and stasis, meaning "stable"), the body's natural tendency to keep things delightfully status quo, even in the face of major changes or outside influences on one part of it. Regulated largely by the endocrine and nervous systems, homeostasis is a combined effort across many bodily levels, from organ to tissue to organism level to keep things in balance.
When homeostasis is compromised it seriously throws things out of whack, causing everything from mental disturbances to mild discomfort to death. So when the body is presented with an abnormal stimulus that threatens to do harm to the delicate internal balance, such as major stress, blood loss or toxin exposure, homeostasis shifts into overdrive to fight back. Here are five prime examples of homeostasis doing its finest work: