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How do ion channels in thermoreceptors trigger an action potential?

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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 thermoreceptors, the process of triggering an action potential is driven by a specialized superfamily of proteins known as transient receptor potential (TRP) channels. These proteins function as ion channels located within the cell membranes of sensory neurons.12

When these channels detect specific thermal stimuli—such as warmth, noxious heat, or cold—they undergo a conformational change that regulates the flow of ions, including potassium, calcium, and sodium, into or out of the cell. This resulting ion flux alters the electrical charge across the cell membrane, causing depolarization, which is a reduction in the negative charge within the cell.12

Once this depolarization reaches a sufficient threshold, it triggers an action potential. This brief electric polarization generates a nerve impulse that is then conveyed to the brain, where it is processed into a physiological sensation or perception of temperature.12