thermoreceptor

Thermoreceptors are sensory neurons that detect changes in temperature. They are found in the skin and other tissues, and there are central thermoreceptors in the brain that monitor core temperature. In the skin, thermoreceptors are free nerve endings that respond to warmth or cold and transmit information to the central nervous system to influence behavior and autonomic responses.

Peripheral thermoreceptors are categorized as warm receptors and cold receptors. Warm receptors respond to increasing temperatures, typically from about 30 C up to the limit of physiological tolerance, while cold receptors respond to decreasing temperatures, from about 35 C downward. Some receptors respond to noxious heat or cold at extremes.

Molecular transduction is mediated by temperature-sensitive ion channels in the nerve endings, particularly members of the transient receptor potential (TRP) family. TRPV1 is activated by heat and capsaicin, TRPM8 by menthol and cool temperatures, and TRPA1 has roles in cold sensation and chemical irritants. Activation of these channels generates receptor potentials and action potentials that encode temperature information.

Signal transmission follows the primary afferent fibers to the dorsal horn of the spinal cord or brainstem, then to higher centers such as the thalamus and somatosensory cortex, which contribute to perception of temperature. Central thermoreceptors in the preoptic area and other hypothalamic regions regulate body temperature by coordinating autonomic and endocrine responses, including vasomotion, sweating, shivering, piloerection, and behavioral adjustments.

Clinical relevance: Thermoreceptive function can be affected by neuropathies, diabetes, aging, and certain medications. Fever results from a rise in the hypothalamic set point in response to pyrogens, rather than a change in skin thermoreceptors.