The human body has the ability to regulate its temperature so that it remains very close to 37 c. If the body is overheating as a result of strenuous exercise, the surface blood vessels dilate to increase the blood flow to the surface areas. Heat is carried by the blood to the surface where it causes the skin temperature to increase. The body also begins to produce sweat. The rate of sweating increases strongly with body temperature above 370c. Rate of sweating 36. 37.0 37.3 Eardrum Temperature/ 'C Conduction, evaporation, convection, and radiation can now transfer heat from the skin to the environment. The chart below shows the relative importance of these heat transfer mechanisms at different environmental temperatures. 100 -radiation and convection percentage of total heat loss 50 evaporation NO 25 30 35 environmental temperature / 'C Relative importance of modes of body heat loss Questions: . For environmental temperature below 32 C, convection and radiation are the dominant heat removal mechanisms. What can a person do to increase the amount of heat carried away by these mechanisms? Why is conduction usually not a dominant heat removal mechanism? Can you think of situations when it becomes important? Why do convection and radiation no longer remove heat from the body at environmental temperature above 37 c? Evaporation The body secrets water on to the skin from sweat glands. As this water evaporates, the latent heat of vaporization is removed from the body. The rate of evaporation increases as the degree of saturation of the surrounding air decreases. In warm humid weather, the rate may be so low that a layer of water accumulates on the skin. In still air, the air near the skin will become saturated and evaporation will stop. Evaporation will increase if this saturated air is continually removed by wind or an artificially produced air stream. Questions: If there is a cool wind blowing, what would be the consequences, as far as heat loss from the body is concerned, of wearing wet clothes? Explain your answer. Cloudy nights are us armer than