The situation is quite different when you are hot (exer-
cising vigorously, have a fever, or are outside on a sunny sum-
mer day): the system senses the increase in temperature.
The response of the body is to decrease heat production and
increase heat loss. As a result, body temperature decreases
to normal (Figure 14.19).
N e g a t i v e - f e e d b a c k m e c h a n i s m s t h a t d e c r e a s e h e a t p r o d u c t i o n a n d
i n c r e a s e h e a t l o s s in r e s p o n s e t o i n c r e a s i n g b o d y t e m p e r a t u r e •
F ig u r e 1 4 . 1 9
Vasodilation
increases heat loss
through skin by
radiation and
conduction
Sweat glands secrete
sweat and remove
heat by evaporation
Decreased thyroid
hormone levels
lower BMR
Put It Togeth<M f
Decrease in body temperature
How might
drugs that cause vasoconstric-
tion affect your heat tolerance?
a. Reduce heat tolerance be-
cause they would inhibit blood
flow and sweating
b. Increase heat tolerance by
increasing blood flow and
sweating
c. No effect
The Heat from Metabolism Must Be Regulated 429
previous page 464 Craig Freudenrich, Gerard J  Tortora   Visualizing Anatomy and Physiology   2011 read online next page 466 Craig Freudenrich, Gerard J  Tortora   Visualizing Anatomy and Physiology   2011 read online Home Toggle text on/off