Homeostasis is defined as which of the following?

• A. Maintenance of relatively stable internal conditions despite continuous changes in environment
• B. Constant external conditions
• C. Immediate response to a stimulus
• D. Imbalance in internal conditions

Answer: (A)

Maintaining relatively stable internal conditions in the face of ongoing changes in the environment is what homeostasis means. The body keeps variables such as temperature, pH, fluid balance, and blood glucose within narrow ranges using sensors, control centers, and effectors. When a variable drifts from its set point, feedback mechanisms work to bring it back toward normal, forming a continuous regulation process. This is different from simply having constant external conditions, and it’s more than a single immediate response to a stimulus. It also contrasts with an imbalance in internal conditions, which would indicate a disruption of homeostasis. Examples include sweating to cool the body when it’s hot or shivering and constricting blood vessels to conserve heat when it’s cold, as well as hormonal regulation of blood glucose by insulin and glucagon.