Section II. MECHANISMS FOR THE REGULATION OF TEMPERATURE
IN THE HUMAN BODY
Human beings, other mammals, and birds are homeothermic or warm- blooded
which means that they are capable of maintaining a body temperature that is nearly
constant. A human being's body temperature is maintained by very precise and
complicated mechanisms. These mechanisms are dominated by a small sensory
structure--the "human thermostat"--which is located in the front part of the
hypothalamus of the brain. This human thermostat or temperature regulating center is
sensitive to changes in temperature in the blood and peripheral receptors for warmth or
cold in the skin. In order to maintain the constant temperature, body temperature is
regulated in two ways: heat production and heat dissipation.
a. Heat Produced by the Body. Most of the heat produced by the body comes
from oxidation of the food we eat. Metabolic rate is the term for the rate at which the
heat is produced. The rate at which heat is produced depends on the following:
Muscular activity. Exercise increases heat production.
Glandular rate. The higher a person's metabolism rate the more heat
(3) Food intake. Some types of food such as foods containing sugar are
burned up more quickly than other foods, thus producing more body heat.
(4) External temperature. The body reacts to environmental temperature. If
the temperature of the environment (air, water) is hot, the body reacts accordingly and
(5) Certain hormones. Certain hormones may increase a person's
metabolic rate, thus increasing that person's heat production.
b. Heat Produced by Tissues. Tissues are responsible, in part, for heat
production. Skeletal muscle tissue contractions produce heat and are an important part
of the homeostatic mechanism for maintaining normal body temperature. During a
skeletal muscular contraction, only 20 or 30 percent of the total energy released is used
for mechanical work. The rest of the energy is released as heat. Two types of heat
energy are produced: initial heat--produced by the contraction and relaxation of a
muscle; recovery heat--produced after relaxation of a muscle.