Which response is primarily promoted by cold thermoreceptors (TRPM8) during cold exposure?

• A. Vasoconstriction and shivering
• B. Vasodilation and sweating
• C. Increased heat loss through respiration only
• D. No change in thermoregulatory responses

Answer: (A)

Cold is detected by TRPM8 channels on sensory nerves, which send signals to the brain to defend body heat. The main reflexes activated are constriction of skin blood vessels and shivering. Vasoconstriction lowers skin blood flow, reducing heat loss to the environment, while shivering rapidly generates heat through muscle activity. These two responses are the primary ways the body maintains core temperature during acute cold exposure.

Vasodilation and sweating occur when the body needs to cool down, not when it’s cold, so they aren’t the primary responses here. Increasing heat loss through respiration isn’t the key mechanism driving cold defense, and a lack of thermoregulatory response isn’t accurate—the body actively mobilizes these heat-conserving and heat-producing actions.