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The Endocrine System
By Jennifer Kenny
When you think of a system in the body that responds to stimuli, you think of the
nervous system. In its own way, the endocrine system responds as well. Instead of electrical
messages, though, it sends messages using chemicals.
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The endocrine system controls body functions with the help of glands that release chemicals.
A gland is a group of cells that produce these chemicals. These special chemicals are called
hormones. Hormones are released into the bloodstream in order to be carried to other places in
the body.
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Perhaps the most famous of the endocrine glands are your adrenal glands. They make the
hormone adrenaline (also called epinephrine). It speeds up your heartbeat and breathing rate so
you can escape danger or fight. The effect you get is called a fight-or-flight response.
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Other glands have different jobs as well. Your pituitary gland works with skeletal growth,
amount of water in the blood, and the birth process. The thyroid gland increases the rate at
which you use energy. The parathyroid glands regulate calcium levels. The thymus gland
controls the immune system. The pancreas controls levels of blood sugar. The ovaries (in
women) and the testes (in men) are involved in reproduction.
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Endocrine glands know when to start and stop releasing hormones because of feedback
controls. These feedback controls let the glands know when to stop sending a particular
hormone. For example, the pancreas is able to know how much insulin your body needs and,
therefore, can stop sending it when blood sugar returns to normal and more insulin is not
necessary.
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Sometimes, though, hormones can become imbalanced. For example, if a person's pancreas
can't make enough insulin, that individual is considered diabetic and may need insulin shots. If a
child's pituitary gland doesn't work properly, a child may be very short or very tall as a result. If
a person's thyroid gland doesn't work correctly, the consequence might be that the person is very
tired or gains weight. Properly working glands are, therefore, essential to good health.
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Name _____________________________
Date ___________________
The Endocrine System
1. What hormone is produced by the pancreas?
2. If an individual can't produce insulin, that person has ___________.
3. Feedback controls stop and start hormone release.
False
True
4. The endocrine system communicates with other systems using electrical impulses.
False
True
5. Epinephrine is another name for ___________.
6. A ___________ is a group of cells that produce hormones.
7. Which hormone is associated with the fight-or-flight response?