Body Temperature Regulation
Chapter 6 Sections 4
Objectives
• Explain how the skin helps to regulate body
temperature
• Describe wound healing
• Distinguish among the types of burns, including a
description of healing with each type
What is Normal Body Temperature?
• Most people think of a "normal" body temperature as an oral
temperature of 98.6°F (37°C).
• This is an average of normal body temperatures.
• Your temperature may actually be 1°F (0.6°C) or more above or
below 98.6°F (37°C).
• Also, your normal body temperature changes by as much as 1°F
(0.6°C) throughout the day, depending on how active you are
and the time of day.
• Body temperature is very sensitive to hormone levels and may
be higher or lower when a woman is ovulating or having her
menstrual period
Regulation of Body Temperature
• Is vitally important to maintain metabolic functions
• Even a slight temperature shift can slow down or speed up
metabolic reactions
• The deeper body parts remain close to a set point of 37°C or
98.6°F
• The maintenance of a stable temperature requires that the
amount of heat the body loses be balanced by the amount it
produces
• The skin is responsible for maintaining the balance
Heat Production
• Heat is a product of cellular metabolism
• The major heat producers are skeletal muscle, cardiac muscle
and liver cells
• When body temperature rises above the set point, the nervous
system stimulates structures in the skin and other organs to
release heat
An Example
• During physical activity active muscle release heat, which the blood
carries away
• The warmed blood reaches the hypothalamus of the brain, which controls
the set point of body temperature
• The hypothalamus signals muscles in the walls of dermal blood vessels to
relax
• As these vessels dilate (vasodilation), more blood enters them, and some
of the heat the blood carries escapes to the outside
• At the same time, the deeper blood vessels contract (vasoconstriction),
diverting blood to the surface and the skin reddens
• The heart is stimulates to beat faster, moving more blood out the deeper
regions
Heat Loss--Radiation
• The primary means of
body heat loss is
radiation, by which
infrared hear rays
escape from warmer
surfaces to cooler
surroundings
• These rays radiate in all
directions
Heat Loss—Conduction & Convection
• Conduction and convection release less heat than does
radiation
• In conduction, heat moves from the body directly into the
molecules of cooler objects in contact with its surface
• For example, heat is lost by conduction into the seat of a
chair when a person sits down
• In convection, continuous circulation of air over a warm
surface causes the air to become heated as it moves away
from the body
Heat Loss--Evaporation
• When the body temperature rises above normal, the nervous
system stimulate eccrine sweat glands to release sweat onto
the surface of the skin
• As this fluid evaporates (changes from a liquid to a gas), it
carries heat away from the surface, cooling the skin
Heat Loss Summary
Body Temperature Drops
• When the body temperature drops below the set point, muscles in the walls
of dermal blood vessels are stimulated to contract
• This action does the following:
• Decreases the flow of heat-carrying blood through the skin
• Cause the skin to lose color
• Helps to reduce heat loss by radiation, conduction and convection
• sweat glands remain inactive, decreasing heat loss by evaporation
• If the body temperature continues to drop, the nervous system will stimulate
skeletal muscle cells throughout your body to contract slightly, increasing
cellular respiration and production of heat
• If this response is not enough to raise the body temperature back to normal,
small groups of muscles rhythmically contact with greater force, causing you
to shiver
Process of Body Temperature Regulation
Problems in Temperature Regulation
• Sometimes the temperature-regulating mechanism does not work
effectively
• Such as on hot humid days when the air becomes saturated with water
vapor
• When this happens, sweat glands may be activated, but the sweat cannot
quickly evaporate
• Thus, you are wet but still hot and uncomfortable
• In addition, if the air temperature is too high heat loss by radiation is
less effective and a person can gain heat from the surroundings
• Two dangerous situations can occur when temperature regulation fails:
• Hyperthermia
• Hypothermia
Hyperthermia
• Occurs when the core body temperature exceeds 106°F
• The skin becomes dry, hot and flushed
• The person can experience feelings of weakness, become dizzy
and nauseous, have a headache, and a rapid, irregular pulse
Hypothermia
• Better known as lowered body temperature
• Results from prolonged exposure to cold or as part of an illness
• It begins with shivering and a feeling of coldness
• If not treated, it progresses to mental confusion, lethargy, loss of
reflexes, loss of consciousness, and eventually the complete
shutdown of your vital organs
• Even if your body’s core temperature drops only a few degrees,
fatal respiratory failure or heart arrhythmia
• Your extremities can withstand drops of 20°F to 30°F below normal
• Some people are more prone to this because of less adipose tissue
beneath the skin, advance age, too thin, and the homeless