homeostasis

noun2

1. •
   The ability of a system or living organism to adjust its internal environment to maintain a state of dynamic constancy; such as the ability of warm-blooded animals to maintain a stable temperature.

   • When homeostasis is disrupted by an external stressor - such as injury, lack of nutrients, or invasion by parasites or other organisms - illness may occur. — 2011
2. •
   Such a dynamic equilibrium or balance.