THERMOREGULATION
Control of body temperature
© 2008 Paul Billiet ODWS
Core temperature
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The core temperature of the human body is
37°C
The core of the human body includes the
organs of the thorax, abdomen and the head
This is where the vital organs are located
Their enzyme systems must operate in
optimum conditions
The periphery of the body can withstand
some deviation from the core temperature
© 2008 Paul Billiet ODWS
Heat loss and heat gain
The body must balance its heat budget
Heat is gained:
 by conduction from warm air surrounding the body
 by the body’s metabolic activity which generates heat
e.g. when muscle move
Heat is lost:
 by conduction and radiation to cold air (or water)
 by evaporation of sweat from the body surface
(c.f. properties of water)
 Humans can also affect their body temperature by
changing their behaviour
e.g. wearing different clothes, seeking shade
© 2008 Paul Billiet ODWS
Maintaining the body temperature
Keeping warm
Staying cool
Increased insulation,
subcutaneous fat reduces
the conduction of heat from
the body
Increase blood flow to skin,
increases conduction and
radiation of heat from the
body
Reduced sweating
decreases evaporation
Increased sweat secretion,
increases evaporation
Increased shivering,
increases heat produced by
muscle tissue 2 to 5 times
Reduced activity
© 2008 Paul Billiet ODWS
Core body
temperature
>37°C
Thermoreceptors
Hypothalamus
nerves
Muscles
reduce
activity
Sweat
glands
increase
secretion
Muscles of
skin arteriole
walls relax
Skin arteries dilate
More blood to the
skin.
More radiation &
conduction of heat
More water covers the
skin.
More evaporation
Less heat generated
© 2008 Paul Billiet ODWS
NEGATIVE
FEEDBACK
Thermoreceptors
Core body
temperature
>37°C
Thermoreceptors
Blood
temperature
Muscles of
skin
arteriole
walls relax
nerves
Hypothalamus
Sweat
glands
increase
secretion
Muscles
reduce
activity
© 2008 Paul Billiet ODWS
Body
loses
heat
Return
to 37°C
Core body
temperature
<37°C
Thermoreceptors
Hypothalamus
nerves
Muscles
shivering
nerves
Sweat
glands
decrease
secretion
Muscles of
skin arteriole
walls
constrict
Less water covers the
skin.
Less evaporation
More heat
generated
© 2008 Paul Billiet ODWS
Skin arteries
constrict
Less blood to the
skin.
Less radiation &
conduction of heat
NEGATIVE
FEEDBACK
Thermoreceptors
Blood
temperature
Muscles of
skin
arteriole
walls
constrict
nerves
Core body
temperature
<37°C
Thermoreceptors
Sweat
glands
decrease
secretion
Hypothalamus
nerves
© 2008 Paul Billiet ODWS
Muscles
shivering
Body
loses
less
heat
Body
gains
heat
Return
to 37°C