Thermoregulation requires the normal function of heat -
production processes. Heat is produced in the body by metabolism which is the chemical reaction in all body cells. Activities requiring additional
chemical reactions increase the metabolic rate.
As metabolism increases additional heat is produced. When
metabolism decreases, less heat is produced. Heat production occurs during
rest, voluntary movements and involuntary shivering (shivering is an
involuntary body response to temperature
differences in the body). Shivering can increase heat production 4 to 5 times
greater than normal.
is produced to equalize body temperature.
Heat production and heat loss occur simultaneously. The
skin' s structure and exposure to the environment result in constant, normal
heat loss through reduction, conduction, convection and evaporation.
Radiation is the transfer of heat from the surface of another without actual contact between
the two. Peripheral vasodilatation increases blood flow to the skin to increase
Peripheral vasoconstriction minimizes blood flow to the skin
and inhibits heat loss.
is the transfer of heat from one
object to another with direct
is the transfer of heat away by air movement. Heat is first conducted to
air molecules directly in contact with the skin. Air current carry away the
is the transfer of heat energy when
a liquid is changed to a gas. The
body continuously losses heat by evaporation. About 600 - 900 ml of water
evaporates from skin and lungs daily, resulting in water and heat loss.
By regulating sweating, the body promotes additional
evaporation and heat loss. When body temperature rises, the anterior
hypothalamus signals the sweat glands to release sweat to evaporate from the
resulting in heat loss.