300 Chapter 12
- Testosterone also causes the development of the
secondary male sex characteristics like facial and
chest hair, muscle development, low-pitched voice,
broad shoulders, and narrow hips.^
- The ovaries produce the female sex hormones,
estrogen and progesterone.^
- Estrogen and progesterone cause the development of
the female reproductive organs. They also cause the
development of the secondary female sexual
characteristics like breast enlargement, high-pitched
voice, broad hips, and fat deposits on the thighs, hips,
and legs.^
- Female sex hormones also control the menstrual
cycle.
The Thymus Gland and Its Hormone
- The thymus gland produces the hormone thymosin,
and the gland is crucial to the development of the
immune system.^
2.^ Thymosin causes the production of the^
T lymphocyte white blood cells, which protect
the body against foreign microbes.
The Pineal Gland and Its Hormone
- The pineal gland is found in the brain near the
thalamus and produces the hormone melatonin.^
- Melatonin inhibits the functions of the reproductive
system and regulates body rhythms like wake and
sleep patterns.^
3.^ Bright light inhibits melatonin secretion.^
4. Low levels of melatonin in bright light make us feel
good and increases fertility; high levels of melatonin in
dim light causes us to feel tired and depressed.^
- The pineal gland also secretes serotonin, a
neurotransmitter and vasoconstrictor.
Review Questions
*1. Explain how the hypothalamus of the brain
controls- the endocrine system.^
*2. Explain how a negative feedback system functions
in maintaining hormonal levels in the body.
- Name the three chemical categories for classifying
hormones and give some examples.^ - Name the major endocrine glands and their
hormones.^ - Name some effects that testosterone has on the
male body.
*Critical Thinking Questions
Matching
Place the most appropriate number in the blank
provided.
Thyroid 1. Thyrotropic (^)
Prolactin hormone (^)
Adrenal medulla 2. Parathormone (^)
Anterior pituitary 3. Testosterone (^)
Adrenal cortex 4. Insulin (^)
Testis 5. Vasopressin (ADH) (^)
Ovary 6. Thyroxine (^)
Parathyroid 7. Estrogen and (^)
Pancreas
8.
progesterone (^)
Posterior pituitary Adrenaline/ (^)
epinephrine (^)
9.^ Cortisol^
10.^ Melatonin^
11.^ Milk secretion^
12. Serotonin
Search and Explore
● Visit the Endocrineweb website at
http://www.endocrineweb.com and read
more about the structures and diseases of
the endocrine system.^
● Visit the American Diabetes Associa-tion
at http://www.diabetes.org to learn more
about type 1 and type 2 diabetes. Write a
two to three paragraph entry in your
notebook comparing the differ-ences
between the two types.