Which concept is described by the maintenance of stable internal conditions despite changes in the external environment?

• A. Process of digestion.
• B. Maintenance of internal stability.
• C. Movement of muscles.
• D. Hormonal balance only in the endocrine system.

Answer: (B)

Homeostasis is the body's ability to keep internal conditions steady despite changes in the external environment. The description that fits this idea is the maintenance of stable internal conditions in the face of outside fluctuations. The body does this by sensing changes, comparing them to a set point, and activating responses that restore balance. For example, when the environment gets hot, mechanisms like sweating and increased blood flow to the skin help dissipate heat to keep core temperature within a narrow range. This balance is achieved through negative feedback loops that counter the deviation from the desired state.

Other options describe specific functions rather than the overarching idea of keeping internal conditions stable. Digestion focuses on breaking down food, movement of muscles concerns locomotion, and while hormonal balance is a regulatory process, the broad concept of maintaining internal stability encompasses more than any single system.