Regulation of Body Temperature Role of the Hypothalamus

Figure 73-6 shows what happens to the body "core" temperature of a nude person after a few hours' exposure to dry air ranging from 30° to 160°F. The precise dimensions of this curve depend on the wind movement of the air, the amount of moisture in the air, and even the nature of the surroundings. In general, a nude person in dry air between 55° and 130°F is capable of maintaining a normal body core temperature somewhere between 97° and 100°F.

The temperature of the body is regulated almost entirely by nervous feedback mechanisms, and almost all these operate through temperature-regulating centers located in the hypothalamus. For these feedback mechanisms to operate, there must also be temperature detectors to determine when the body temperature becomes either too high or too low.

Atmospheric temperature (°F)

Figure 73-6

Atmospheric temperature (°F)

Figure 73-6

Effect of high and low atmospheric temperatures of several hours' duration on the internal body "core" temperature. Note that the internal body temperature remains stable despite wide changes in atmospheric temperature.

Role of the Anterior Hypothalamic-Preoptic Area in Thermostatic Detection of Temperature

Experiments have been performed in which minute areas in the brain of an animal have been either heated or cooled by use of a thermode. This small, needle-like device is heated by electrical means or by passing hot water through it, or it is cooled by cold water. The principal areas in the brain where heat or cold from a thermode affects body temperature control are the preoptic and anterior hypothalamic nuclei of the hypothalamus.

Using the thermode, the anterior hypothalamic-preoptic area has been found to contain large numbers of heat-sensitive neurons as well as about one third as many cold-sensitive neurons. These neurons are believed to function as temperature sensors for controlling body temperature. The heat-sensitive neurons increase their firing rate 2- to 10-fold in response to a 10°C increase in body temperature. The cold-sensitive neurons, by contrast, increase their firing rate when the body temperature falls.

When the preoptic area is heated, the skin all over the body immediately breaks out in a profuse sweat, while the skin blood vessels over the entire body become greatly dilated. This is an immediate reaction to cause the body to lose heat, thereby helping to return the body temperature toward the normal level. In addition, any excess body heat production is inhibited. Therefore, it is clear that the hypothalamic-preoptic area has the capability to serve as a ther-mostatic body temperature control center.

Detection of Temperature by Receptors in the Skin and Deep Body Tissues

Although the signals generated by the temperature receptors of the hypothalamus are extremely powerful in controlling body temperature, receptors in other parts of the body play additional roles in temperature regulation. This is especially true of temperature receptors in the skin and in a few specific deep tissues of the body.

It will be recalled from the discussion of sensory receptors in Chapter 48 that the skin is endowed with both cold and warmth receptors. There are far more cold receptors than warmth receptors—in fact, 10 times as many in many parts of the skin. Therefore, peripheral detection of temperature mainly concerns detecting cool and cold instead of warm temperatures.

When the skin is chilled over the entire body, immediate reflex effects are invoked and begin to increase the temperature of the body in several ways: (1) by providing a strong stimulus to cause shivering, with a resultant increase in the rate of body heat production; (2) by inhibiting the process of sweating, if this is already occurring; and (3) by promoting skin vasoconstriction to diminish loss of body heat from the skin.

Deep body temperature receptors are found mainly in the spinal cord, in the abdominal viscera, and in or around the great veins in the upper abdomen and thorax. These deep receptors function differently from

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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  • CECIL
    What are the roles of hypothalamus in regulation of body temperature?
    2 years ago
  • Kelsi
    What is the role of the hypothalamus for regulation of body temperature?
    10 months ago
  • sabine vogt
    Which part of hypothalamus detects cold?
    6 months ago
  • Fre-Swera
    What is the role in regulating temperature?
    2 months ago
  • jarmo
    What is the role of the hypothalamus and the skin in the regulation of body temperature?
    12 days ago
  • Noemi
    What is the detector and response for body temp?
    8 days ago

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