Behavioral Control of Body Temperature
Aside from the subconscious mechanisms for body temperature control, the body has another temperature-control mechanism that is even more potent. This is behavioral control of temperature, which can be explained as follows:
Whenever the internal body temperature becomes too high, signals from the temperature-controlling areas in the brain give the person a psychic sensation of being overheated. Con-versely, whenever the body becomes too cold, signals from the skin and probably also from some deep body receptors elicit the feeling of cold discomfort. There-fore, the person makes appropriate environmental adjustments to re-establish comfort, such as moving into a heated room or wearing well-insulated clothing in freezing weather. This is a much more powerful system of body temperature control than most physiologists have acknowledged in the past. Indeed, this is the only really effective mechanism to prevent body heat control breakdown in severely cold environments.
When a person places a foot under a hot lamp and leaves it there for a short time, local vasodilation and mild local sweating occur. Conversely, placing the foot in cold water causes local vasoconstriction and local ces-sation of sweating. These reactions are caused by local effects of temperature directly on the blood vessels and also by local cord reflexes conducted from skin recep-tors to the spinal cord and back to the same skin area and the sweat glands. The intensity of these local effects is, in addition, controlled by the central brain tempera-ture controller, so that their overall effect is propor-tional to the hypothalamic heat control signal times the local signal. Such reflexes can help prevent excessive heat exchange from locally cooled or heated portions of the body.
Regulation of Internal Body Temperature Is Impaired by Cuttingthe Spinal Cord. After cutting the spinal cord in the neckabove the sympathetic outflow from the cord, regulation of body temperature becomes extremely poor because the hypothalamus can no longer control either skin blood flow or the degree of sweating anywhere in the body. This is true even though the local temperature reflexes originating in the skin, spinal cord, and intra-abdominal receptors still exist. These reflexes are extremely weak in comparison with hypothalamic control of body temperature.
In people with this condition, body temperature must be regulated principally by the patientâ€™s psychic response to cold and hot sensations in the head regionâ€” that is, by behavioral control of clothing and by moving into an appropriate warm or cold environment.