Temperature regulation

You will be presented with four graphs. The first two represent body temperature and skin temperature, the two variables which form the input to the thermoregulation system. The other two are sweating rate, and the blood flow to the skin, which are the two main 'plants' of the thermoregulation system, i.e., they actually cause changes that represent the output of the control system.

You will also see four variables on the right which you can vary manually; these represent the environment. By altering the environment, you can change the body and skin temperature, and see the response produced by the body.

Here are the 'equations' that govern the system:

• Body temperature is increased by metabolic processes. The metabolic rate is dependent on exercise, thyroxine, and on body temperature itself (at higher temperatures, metabolism is faster).
• Skin temperature equilibrates towards environment temperature at a rate determined by the clothing index,
• but also equilibrates towards body temperature at a rate determined by skin blood flow.
• Skin temperature is also reduced by evaporation rate, which is proportional to sweating rate, but reduced by a high clothing index, and also depends on the environment temperature and environment humidity.
• The skin blood flow is the product of Skin vascular resistance and arterial pressure.
• Both the Sweating rate and skin vascular resistance are proportional to the error in both skin temperature and body temperature.