Temperature sensations are detected by specialized free nerve endings called cold receptors and warm receptors. Cold receptors respond to decreasing temperature and warm receptors respond to increasing temperatures. Cold receptors are most sensitive to temperatures between 50°F (10°C) and 68°F (20°C). Temperatures below 50°F (10°C) stimulate pain receptors, producing a freezing sensation. Warm receptors are most sensitive to temperatures above 77°F (25°C) and become unresponsive at temperatures above 113°F (45°C). Temperatures near and above 113°F (45°C) stimulate pain receptors, producing a burning sensation. Both warm and cold receptors rapidly adapt. Within about a minute of continuous stimulation, the sensation of warmth or cold begins to fade.