in the forebrain) to release adrenocorticotropic hor-
mone (ACTH), and ACTH stimulates the adrenal
cortex of the adrenal gland to secrete glucocorti-
coids. The most important glucocorticoid where
stress is concerned is cortisol. Cortisol is a hormone
that, like epinephrine and norepinephrine, mobilizes
the body’s resources. Cortisol serves primarily to
increase energy level and decrease inflammation.
The latter function is particularly useful if injuries
are sustained in an urgent situation.
Although responses of the body to stress can be
helpful, severe stress and prolonged activation of
these systems can have adverse effects on body
organs, mental functions, and the immune system.
For example, stress can affect the immune system
so that it cannot effectively destroy viruses, bacteria,
tumors, and irregular cells. More than two decades
ago, Ader and Cohen (1975) presented evidence
suggesting that the nervous system and the immune
system interact and are interdependent by demon-
strating that immune system responses in rats could
be classically conditioned. This initial report eventu-
ally led to a number of studies investigating the rela-
tionship between physiological factors (e.g., reactionsF I G U R E 17-2 Physiological effects of stress
SOURCE: Brannon, L., & Feist, J. (2010).Health psychology: An introduction to behavior and health(7th ed.). Pacific Grove, CA: Brooks/Cole. Page 100. Used
with permission.
490 CHAPTER 17