Biology 12

Chapter 6 The Endocrine System • MHR 183

children. The thymus gland produces thymosin, a
hormone that stimulates the production and
maturation of lymphocytes into T cells. The
thymus gland normally disappears after puberty.
(In adults, lymphocytes continue to be produced by
the spleen and lymph glands.) The pituitary gland
regulates hormone production in the thymus gland.
If the pituitary gland is surgically removed, the
thymus gland will atrophy (shrink).
In this section, you learned that the pituitary
gland is aptly named the master gland. You saw
that the pituitary gland is the essential link
between the nervous system and the endocrine
system. This gland regulates the activities of other
endocrine organs in the body. The next section
examines the adrenal glands and their role in

managing the body’s physiological response to

stressful situations.

http://www.mcgrawhill.ca/links/biology12

Nicotine, alcohol, and caffeine are considered to be drugs that

can alter the production and effectiveness of hormones

secreted by endocrine organs. To access information about

how these substances act on the endocrine system, go to the

web site above, and click on Web Links. Compare the effects of

nicotine, alcohol, and caffeine on the production and secretion

of the following hormones: thyroxine; cortisol; ACTH; and

insulin. How do these changes in hormone function affect

metabolic activity (for example, heart rate, absorption of

nutrients, and basal metabolic rate)?

WEB LINK

SECTION REVIEW

1. Describe how hormones secreted by glands of
   the endocrine system regulate metabolic rate.


2. (a)How is an exocrine gland different from an
   endocrine gland?
   (b)Identify two organs in the body that act as both
   endocrine and exocrine glands.


3. In a chart, list the hormones produced in the
   human body. Divide the list into two sections:
   steroid and non-steroid hormones. Describe the
   substances used by the body to manufacture
   non-steroid hormones.


4. Compare the way steroid and non-steroid
   hormones affect cellular activity.


5. Explain why adequate lipid intake is essential
   for the normal function of some endocrine glands
   and hormones.


6. Identify the endocrine glands and hormones
   responsible for regulating blood pressure in the
   circulatory system.


7. Make a chart to list the similarities and differences
   between the roles of the endocrine system and the
   nervous system.
   8. Describe the difference between
   hyperthyroidism and hypothyroidism.
   9. Design a study to investigate how medications
   that inhibit the normal metabolism of iodine in the
   body can be used to treat hyperthyroidism.


8. Make an outline diagram of the human body. In
   the diagram, draw the approximate shape of each
   endocrine gland (to scale) in its correct location within
   the body. Label the hormones produced by each
   gland and use arrows to show the target organs and
   tissues of each hormone.


9. Some studies indicate that normal endocrine
   function in people and other animals can be
   disrupted by exposure to industrial toxins, such as
   dioxins and PCBs, at the prenatal or infant stage of
   development. These toxins interfere with growth or
   lead to neurological disorders, including learning
   difficulties. Identify hazardous substances in your
   area. List strategies to minimize exposure to these
   substances. What long-term changes are needed to
   radically reduce the degradation of the environment?

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