Page 219 - Industrial Ventilation Design Guidebook

I 80 CHAPTER 5 PHYSIOLOGICAL AND TOXICOLOGICAL. CONSIDERATIONS
the body. In addition, there is evidence that temperature sensors in the spinal
8
cord and gut also give the hypothalamus core temperature information. The
skin has abundant numbers of warm and cold sensors that also communicate
to the hypothalamus (Fig. 5.2).

Thermal Sensation
The temperatures monitored in Fig. 5.2 are used by the brain to regulate
shivering, blood flow to the skin, and sweating. The sensed temperatures also
contribute to our overall feelings of warmth and other thermal sensations.
Thermal sensation (TS) can be predicted over a wide range of activities (0.8 to
4 met) from simple deviations in the mean body temperature (T mll) from the
mean body temperature when the person feels neither warm or cool but neu-
tral (T mbn) (Fig. 5.2).
The mean body temperature is a weighted average of core and skin tem-
peratures, with core temperature being much more important. That is as it
should be as the purpose of the regulation system's operations is to maintain
core temperature for the brain and other vital organs. The mean body temper-
ature for a neutral thermal sensation is about 36.2 °C. At temperatures above
or below that, one feels progressively warmer or cooler, which further protects
the individual by stimulating conscious behavioral actions to reduce physio-
logical strain and restore neutral sensations.
During transients the rate of change of mean body temperature can have a
strong effect on thermal sensation.

FIGURE 5.2 Temperature sensors for temperature regulation and thermal sensation.