thermoreceptor

thumb|Thermoreceptors of the skin sense the temperature of water A thermoreceptor is a non-specialised sense receptor, or more accurately the receptive portion of a sensory neuron, that codes absolute and relative changes in temperature, primarily within the innocuous range. In the mammalian peripheral nervous system, warmth receptors are thought to be unmyelinated C-fibres (low conduction velocity), while those responding to cold have both C-fibers and thinly myelinated A delta fibers (faster conduction velocity). The adequate stimulus for a warm receptor is warming, which results in an increase in their action potential discharge rate. Cooling results in a decrease in warm receptor discharge rate. For cold receptors their firing rate increases during cooling and decreases during warming. Some cold receptors also respond with a brief action potential discharge to high temperatures, i.e. typically above 45 °C, and this is known as a paradoxical response to heat . The mechanism responsible for this behavior has not been determined.

==Location== In humans, along the axons of Lissauer's tract temperature or pressure sensations enter the spinal cord. The Lissauer's tract will synapse on first-order neurons in grey matter of the dorsal horn, one or two vertebral levels up. The axons of these second-order neurons then decussate, joining the spinothalamic tract as they ascend to neurons in the ventral posterolateral nucleus of the thalamus.