Involuntary muscle contractions that generate heat to raise body temperature in response to cold.

• A. Shivering
• B. Tremors
• C. Rigor
• D. Chills

Answer: (A)

Involuntary rapid muscle contractions generate heat to raise body temperature in response to cold. When the body senses a drop in temperature, the hypothalamus triggers quick, rhythmic contractions of skeletal muscles. Each contraction increases metabolic activity, releasing heat as a byproduct and helping restore core temperature. This response also often involves narrowing of blood vessels to reduce heat loss. This mechanism is specifically about producing heat to warm the body, whereas tremors can occur for other reasons and aren’t the targeted heat-generating process, rigor is a stiffening of muscles not related to thermogenesis, and chills are a subjective sensation of feeling cold rather than the heat-producing action itself.