Cold receptors detect firing rate changes toward which temperature, and what happens below about 10°C?

• A. Increase toward 25°C; below 10°C pain or numbness
• B. Increase toward 46°C; below 10°C heat
• C. Decrease toward 15°C; below 10°C numbness
• D. Remain constant; below 10°C no sensation

Answer: (A)

Cold receptors respond to cooling by increasing their firing rate as skin temperature becomes cooler. As temperature drops toward about 25°C, these receptors fire more vigorously, signaling the sensation of cold. When the temperature falls below roughly 10°C, sensation can change to numbness or cold-induced pain because the nerves and conduction processes are affected by intense cold.

This fits the idea that cold detection involves rising neural activity with cooling, and extreme cold can blunt or alter sensation, whereas heating would not produce this pattern of cold-specific firing.