What is homeostasis?

• A. The maintenance of a stable internal environment within narrow limits.
• B. The process of breaking down nutrients in the digestive system.
• C. The generation of energy by mitochondria.
• D. The study of body structure.

Answer: (A)

Homeostasis is the body's ability to keep its internal conditions stable within narrow limits so cells can function properly. This relies on feedback systems: sensors detect changes, a control center processes the information, and effectors adjust physiology to return conditions toward a desired set point. Examples include regulating body temperature, blood pH, and blood glucose, with responses like sweating or shivering, buffering, and hormone control to keep these factors within a tight range. The other descriptions point to specific processes—digestion breaks down nutrients, mitochondria generate energy through cellular respiration, and anatomy is the study of body structure—so they don’t describe the broader regulation of internal stability that homeostasis refers to.