Thermal receptors are activated by which stimulus?

• A. Cold temperatures
• B. Mechanical pressure
• C. Heat
• D. Chemical mediators

Answer: (C)

Thermal receptors detect changes in temperature in the skin. They come in two kinds: warm receptors that respond to heat and cold receptors that respond to cold. When asked which stimulus activates these receptors, heat is the classic trigger because it engages the warm (thermal) receptors responsible for sensing warmth. Mechanical pressure would activate mechanoreceptors, and chemical mediators would activate chemoreceptors. Cold temperatures would activate the cold receptors, but the question is about what stimulus activates thermal receptors in general, and heat best fits that role.