How does the frequency of thermoreceptor nerve impulses change during cooling?

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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.

In the context of thermoreception, the frequency of nerve impulses in cold receptors changes in two distinct ways during cooling:

Dynamic Response: Upon sudden cooling, cold receptors exhibit a transient increase in discharge frequency. This immediate spike is directly related to the magnitude and rate of the temperature decrease.1
Static Response: If the cooler temperature is maintained, the discharge frequency adapts to a steady state. This static frequency is directly related to the new, cooler temperature.1

Generally, cold-sensitive thermoreceptors show increased activity at temperatures below the neutral skin temperature of approximately 34 °C (93 °F), with many reaching a maximum static discharge frequency between 20–30 °C (68–86 °F). Conversely, when a cold receptor is warmed, it experiences a transient inhibition (decrease) in discharge frequency before adapting to a new static value.1