Homeostasis

Take a West African Dwarf goat out of its pen at six in the morning in Jos, when the Harmattan air is barely fifteen degrees, and again at two in the afternoon, when the sun over the same pen is fierce enough to make a herdsman sweat through his shirt. Measure the goat's own body temperature both times and it barely moves. The outside world swings wildly. The inside of the animal does not, and that quiet stability is not an accident: it is the animal's body actively fighting to hold its internal conditions steady, every second of the day.

In this lesson you will learn what homeostasis means, the general negative-feedback mechanism that every homeostatic correction follows, and how the nervous system and the endocrine system, the two systems you have already met, each play a distinct part in keeping the correction working. Body temperature will be your running example throughout, because thermoregulation is the homeostatic mechanism every stockman meets first and relies on to keep animals alive, growing and productive.