Transmission of Thermal Signals in the Nervous System
In general, thermal signals are transmitted in pathways parallel to those for pain signals. On entering the spinal cord, the signals travel for a few segments upward or downward in the tract of Lissauer and then terminate mainly in laminae I, II, and III of the dorsal horns—the same as for pain. After a small amount of processing by one or more cord neurons, the signals enter long, ascending thermal fibers that cross to the opposite anterolateral sensory tract and terminate in both (1) the reticular areas of the brain stem and (2) the ventrobasal complex of the thalamus.
A few thermal signals are also relayed to the cere-bral somatic sensory cortex from the ventrobasal complex. Occasionally a neuron in cortical somatic sensory area I has been found by microelectrode studies to be directly responsive to either cold or warm stimuli on a specific area of the skin. However, removal of the entire cortical postcentral gyrus in the human being reduces but does not abolish the ability to dis-tinguish gradations of temperature.
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