THE PLANNER^
Adipose tissue releases
leptin, which suppresses
appetite.
Placenta - During pregnancy, the
placenta secretes human chorionic
gonadotropin (hCG), which allows
the ovary to continue secreting
progesterone and estrogen to
maintain pregnancy.
A ll cells exce pt red blood cells secrete
tw o ho rm o n e s th a t are d e rive d from
fa tty acids: le u k o trie n e s (lo o-ko-T R I-
ens)
and
p ro s ta g la n d in s
(pros'-ta-
G L A N -d in s).
U nlike
m ost o th e r h o r-
m ones, th e se act lo ca lly (that is, close
to th e ir sites of release), so th e y are
tfOEtifiEftU&n
the blood. Le u ko trie n e s stim ulate the
m ove m e n t of w h ite blood cells and m e-
flp b lia b
a lte r sm ooth m uscle con tra ction , glan -
dcfebffcy p t
tive pro cesse s, p la te le t fun ction, resp i-
ration, nerve im p ulse tra n sm issio n , fat
m etab olism , and im m u ne responses.
P ro sta g la n d in s also have roles in in-
fCdb ptffs, cch
te n sifyin g pain.
The Endocrine System Coordinates
the Stress response
LEARNING OBJECTIVES
1.
Describe
the stages of the stress response.
2.
List
the glands of the endocrine system in-
volved in the stress response.
I
magine that you are driving to class and you
narrowly avoid a collision with another vehi-
cle. The sound of the other car’s horn startles
you. You immediately realize what happened.
Your heart beats faster and harder. You are breathing more
heavily. You may be sweating. When you get to class, your
professor springs a pop quiz for which you are unprepared,
and the same symptoms appear again. These events are
stressors, and we encounter such events every day. Some
other examples of stress include fear, anxiety, other strong
emotions, exposure to toxins or allergens, changes in tem-
perature, exercise, injury trauma, and disease.
The body has a series of physiological responses to
stress, which is called the stress response, or general ad-
aptation syndrome. The stress response, which has three
stages, strives to maintain homeostasis.
The Stress Response Has
Three Stages
Whatever the cause of stress, the body responds in stages.
The
fig h t-o r-flig h t stage
prepares the body for immediate
physical activity. The
resistance stage
involves prolonged re-
sistance to the stressor. The
exhaustion stage
features an in-
ability to resist prolonged exposure to the stressor.
Let’s look at the responses in each stage.
I
The Endocrine System Coordinates the Stress Response 275
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