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4. Circle the letter of the cells that hormones affect.
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The endocrine system produces
chemicals that control many of the body’s daily
activities. The endocrine system also regulates
long-term changes such as growth and development.
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The endocrine system is made up of glands. A gland is
an organ that makes a chemical. Some glands release
their chemicals into nearby tissues. Endocrine (EN duh
krin) glands release their chemicals into the blood.
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Hormones affect only certain cells. The cells affected by
hormones are called target cells.
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ideas above.
1. Glands that release hormones into the blood are called
glands.
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Each endocrine gland makes different hormones. So,
each gland controls different body activities.
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The hypothalamus (hy poh THAL uh mus) is in the
brain. It controls all the other endocrine glands. The
brain controls the endocrine system by controlling the
hypothalamus.
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The pituitary (pih TOO ih tehr ee) gland is just below the
hypothalamus. It is controlled by the hypothalamus.
Most pituitary hormones control other endocrine glands.
A few pituitary hormones control body activities directly.
For example, the pituitary gland makes growth
hormone, which controls growth in children.
Answer the following questions. Use your textbook and the
ideas above.
5. Is the following sentence true or false? All endocrine
2. Circle the letter of what hormones do.
a. make glands
b. control activities in the body
c. send messages to the brain
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Endocrine glands release hormones when the brain
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The endocrine glands include the
hypothalamus, pituitary, thyroid, parathyroid, adrenal,
thymus, and pancreas. They also include the ovaries
in females and testes in males.
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Chemicals made by endocrine glands are called
hormones. Hormones control activities in the body.
Hormones turn on, turn off, speed up, or slow down
body activities.
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Hypothalamus
Body cells
Thyroid gland
If the thyroid gland were a furnace, the hypothalamus
would be the thermostat. The hypothalamus senses
when cells need more or less energy. The hypothalamus
then signals the pituitary gland to release, or to stop
releasing, a hormone that controls the thyroid gland.
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controls the thyroid gland. Fill in the blank with the
name of the missing gland.
The endocrine system works like a furnace and
thermostat. When a house is cold, the thermostat
signals the furnace to make heat. Once the house is
warm, the thermostat signals the furnace to stop making
heat. This is an example of negative feedback. In
negative feedback, a system is turned on or off by the
conditions that it produces.
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7. How is the endocrine system like a furnace and
thermostat? Circle the letter of the correct answer.
a. Endocrine glands are turned on and off by their own
hormones.
b. Endocrine glands are controlled by body heat.
c. Endocrine glands cannot work if they run out of fuel
from the hypothalamus.
Negative feedback controls the endocrine glands. The
thyroid gland in the neck is a good example. One of the
thyroid’s hormones controls how much energy cells
have. When cells have too little energy, the thyroid gland
releases its hormone. Once cells have enough energy,
the thyroid stops releasing its hormone.
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Answer the following questions. Use your textbook and the
ideas on page 100.
Through negative feedback, when the
amount of a particular hormone in the blood reaches a
certain level, the endocrine system sends signals that
stop the release of that hormone.
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