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P A R T 6
Drugs acting on the endocrine system
calcitonin, in direct response to serum calcium levels.
Many different prostaglandins are released throughout
the body in response to local stimuli in the tissues that
produce them. Activation of the sympathetic nervous
system directly causes release of ACTH and the adreno
corticoid hormones to prepare the body for fight or
flight. Aldosterone, an adrenocorticoid hormone, is
released in response to ACTH but is also released
directly in response to high potassium levels.
As more is learned about the interactions of the
nervous and endocrine systems, new ideas are being
formed about how the body controls its intricate homeo
stasis. When administering any drug that affects the
endocrine or nervous systems, it is important for the
nurse and midwife to remember how closely related all
of these activities are. Expected or unexpected adverse
effects involving areas of the endocrine and nervous
systems often occur.
■■
The hypothalamus and pituitary operate by a
series of negative feedback mechanisms called
the hypothalamic–pituitary axis (HPA). The
hypothalamus secretes releasing factors to cause the
anterior pituitary to release stimulating hormones,
which act with specific endocrine glands to cause the
release of hormones.
■■
Growth hormone and prolactin are released by the
anterior pituitary and directly influence cell activity.
These hormones are regulated by the release of the
hypothalamic inhibiting factors somatostatin and PIF
in response to the levels of the pituitary hormones
growth hormone and prolactin.
■■
Some hormones are not influenced by the HPA and
are released in response to direct local stimulation.
CHAPTER SUMMARY
■■
The endocrine system is a regulatory system that
communicates through the use of hormones.
■■
Because the endocrine and nervous systems are
tightly intertwined in the regulation of body
homeostasis, they are often referred to as the
neuroendocrine system.
■■
A hormone is a chemical that is produced within the
body, is needed in only small amounts, travels to
specific receptor sites to cause an increase or decrease
in cellular activity and is broken down immediately.
■■
As the “master gland” of the neuroendocrine system,
the hypothalamus helps to regulate the central and
autonomic nervous systems and the endocrine system
to maintain homeostasis.
■■
The pituitary is made up of three lobes: anterior,
posterior and intermediate. The anterior lobe
KEY POINTS
produces stimulating hormones in response to
hypothalamic stimulation. The posterior lobe stores
two hormones produced by the hypothalamus—
ADH and oxytocin. The intermediate lobe produces
endorphins and encephalins to modulate pain
perception.
■■
The hypothalamus and pituitary operate by a
series of negative feedback mechanisms called
the hypothalamic–pituitary axis (HPA). The
hypothalamus secretes releasing factors to cause the
anterior pituitary to release stimulating hormones,
which act with specific endocrine glands to cause
the release of hormones or, in the case of growth
hormone and prolactin, to stimulate cells directly. This
stimulation shuts down the production of releasing
factors, which leads to decreased stimulating factors
and, subsequently, decreased hormone release.
■■
Growth hormone and prolactin are released by
the anterior pituitary and directly influence cell
activity. These hormones are regulated by the release
of hypothalamic inhibiting factors in response to
hormone levels or a cellular mediator.
■■
Some hormones are not influenced by the HPA and
are released in response to direct local stimulation.
■■
When any drug that affects either the endocrine or
the nervous system is given, adverse effects may occur
throughout both systems because they are closely
interrelated.
Knowing your strengths and weaknesses helps you to
study more effectively. Take a PrepU Practice Quiz
to find out how you measure up!
ONLINE RESOURCES
An extensive range of additional resources to enhance teaching
and learning and to facilitate understanding of this chapter may
be found online at the text’s accompanying website, located on
thePoint at
These include Watch and
Learn videos, Concepts in Action animations, journal articles,
review questions, case studies, discussion topics and quizzes.
WEB LINKS
Students may want to explore up-to-date information
from the following Internet sources:
Travel through the virtual endocrine system.
Interactive review of the endocrine system and
hormones.
