Relatively constant internal physical and chemical conditions that organisms maintain are called

• A. Emotions
• B. Set point theory
• C. Refractory period
• D. Homeostasis

Answer: (D)

Maintaining stable internal conditions is homeostasis. Organisms keep temperature, pH, glucose, and other internal factors within narrow ranges so cells can function properly. This regulation relies on negative feedback loops: sensors detect a deviation, a control center compares it to a desired value, and effectors adjust processes to bring conditions back toward that target. For example, when the body overheats, sweating and increased blood flow to the skin help cool it; when it’s too cold, shivering and reduced heat loss help raise temperature. This constant regulation keeps enzymes and metabolic processes running smoothly despite changes in the external environment. The other terms refer to different ideas—emotions are subjective experiences, set point theory is a concept about target values in regulation but not the full process, and the refractory period is a brief recovery phase after a neuron fires. The correct term is homeostasis.