Convection is the transference of heat by air movement or body motion. Cool air
making contact with the body is warmed and carried away by convection currents.
More cool air moves over and around the body and is carried away by convection
loses about 15 percent of body heat into the air by this method of heat transfer.
Figure 4-4. Convection--body heat to the air.
4-14. CARDIOVASCULAR ROLE
Blood, one of the parts of the cardiovascular system, is a complex liquid that
performs a number of critical functions. One of these functions is to aid in the regulation
of normal body temperature. Blood contains a large volume of water and is, therefore,
an excellent heat absorber and coolant.
a. Blood flow to the skin plays an important part in heat transference. When the
temperature of the environment is low or a person's blood temperature falls below
normal, impulses from the heat-promoting center of the body stimulate nerves that
cause blood vessels of the skin to constrict (get smaller). This causes a decrease in the
flow of warm blood from the body's internal organs to the skin. This reduction in heat
helps raise the internal temperature of the body. Heat has been retained.
b. When stress, environment, or some other factor causes the body's
temperature to be above normal, impulses stimulate the heat- losing center. Heat
reducing mechanisms are set in motion. Blood vessels in the skin dilate (get bigger).
More warm blood moves to the skin. The skin becomes warm, and the excess heat
radiates out to the environment. The slower metabolic rate helps bring the temperature
of the body down to normal.