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Why do cold receptors remain active at constant cool temperatures?

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thermoreception in polar bears — Thermoreception Warm-blooded animals, such as polar bears, maintain stable body temperatures and adapt to substantial geographic and seasonal temperature fluctuations. Thermal adaptation is supported by the function of sensory structures called thermoreceptors.

Cold receptors remain active at constant cool temperatures because they are continuously active sensory structures that exhibit a steady discharge frequency, known as a static response, which is directly related to the ambient temperature.1

While these receptors respond to sudden cooling with a transient increase in discharge frequency—a dynamic response—they adapt to a specific, ongoing level of electrical activity once a cooler temperature is maintained. This static activity allows the nervous system to monitor the absolute temperature at the receptor site rather than just the rate of change.1

In humans, cold receptors primarily increase their activity at temperatures below the neutral skin temperature of approximately 34 °C (93 °F), with many reaching their maximum static discharge frequency at temperatures between 20 and 30 °C (68–86 °F). This continuous signaling is fundamental to how the body perceives thermal comfort and explores the environment.12