<meta http-equiv="refresh" content="1; url=/nojavascript/"> The Endocrine System | CK-12 Foundation
You are reading an older version of this FlexBook® textbook: CK-12 Biology Workbook Go to the latest version.

# 22.2: The Endocrine System

Difficulty Level: At Grade Created by: CK-12

## Lesson 22.2: True or False

Name___________________ Class______________ Date________

Write true if the statement is true or false if the statement is false.

_____ 1. Steroid hormones can enter the nucleus and influence the expression of genes.

_____ 2. Hormones are chemical messengers.

_____ 3. A target cell is the type of cell that has an effect on hormones.

_____ 4. Non-steroid hormones bind to their receptors in the cytoplasm of the cell.

_____ 5. The pancreas is a large endocrine gland in the neck.

_____ 6. Hypersecretion by an endocrine gland is often caused by a tumor.

_____ 7. Most hormone feedback mechanisms involve positive feedback loops.

_____ 8. Milk production by a mother for her baby is positively regulated.

_____ 9. Type 2 diabetes cannot be treated by insulin injections.

_____ 10. The thyroid gland is often called the “master gland” of the endocrine system.

_____ 11. Secondary messengers affect cell processes inside the cell.

_____ 12. Negative feedback controls insulin secretion by the adrenal gland.

_____ 13. Negative feedback regulation occurs when a product feeds back to decrease its own production.

_____ 14. Endocrine hormones travel throughout the body in the blood.

Name___________________ Class______________ Date________

Read these passages from the text and answer the questions that follow.

Hormone Regulation: Feedback Mechanisms

Hormones control many cell activities, so they are very important for homeostasis. But what controls the hormones themselves? Most hormones are regulated by feedback mechanisms. A feedback mechanism is a loop in which a product feeds back to control its own production. Most hormone feedback mechanisms involve negative feedback loops. Negative feedback keeps the concentration of a hormone within a narrow range.

Negative Feedback

Negative feedback occurs when a product feeds back to decrease its own production. This type of feedback brings things back to normal whenever they start to become too extreme. The thyroid gland is a good example of this type of regulation. It is controlled by the negative feedback loop shown in the FlexBook.

Here’s how thyroid regulation works. The hypothalamus secretes thyrotropin-releasing hormone, or TRH. TRH stimulates the pituitary gland to produce thyroid-stimulating hormone, or TSH. TSH, in turn, stimulates the thyroid gland to secrete its hormones. When the level of thyroid hormones is high enough, the hormones feed back to stop the hypothalamus from secreting TRH and the pituitary from secreting TSH. Without the stimulation of TSH, the thyroid gland stops secreting its hormones. Soon, the level of thyroid hormone starts to fall too low. What do you think happens next? Negative feedback also controls insulin secretion by the pancreas.

Positive feedback

Positive feedback occurs when a product feeds back to increase its own production. This causes conditions to become increasingly extreme. An example of positive feedback is milk production by a mother for her baby. As the baby suckles, nerve messages from the nipple cause the pituitary gland to secrete prolactin. Prolactin, in turn, stimulates the mammary glands to produce milk, so the baby suckles more. This causes more prolactin to be secreted and more milk to be produced. This example is one of the few positive feedback mechanisms in the human body. What do you think would happen if milk production by the mammary glands was controlled by negative feedback instead?

Questions

1. What is a feedback mechanism?

$\\\\\\\\\\$

2. What is negative feedback regulation? Give an example.

$\\\\\\\\\\$

3. What is positive feedback regulation? Give an example.

$\\\\\\\\\\$

4. How are most hormones regulated?

$\\\\\\\\\\$

5. What do you think would happen if milk production by the mammary glands was controlled by negative feedback loop?

$\\\\\\\\\\$

## Lesson 22.2: Multiple Choice

Name___________________ Class______________ Date________

Circle the letter of the correct choice.

1. Glands of the endocrine system include
1. the thyroid gland.
2. the pituitary gland.
4. all of the above.
2. Negative feedback regulation of hormones occurs
1. when a reactant feeds back to decrease its own production.
2. when a product feeds back to increase its own production.
3. when a product feeds back to decrease its own production.
4. when a reactant feeds back to increase its own production.
3. Which statement is true about the thyroid hormones? (1) They increase the rate of metabolism in cells throughout the body. (2)They control how quickly cells use energy. (3) They are not steroid hormones. (4) They are released by the parathyroid glands.
1. 1 only
2. 1 and 2
3. 1, 2, and 3
4. 1, 2, 3, and 4
4. Steroid hormones
1. can influence gene expression.
2. can diffuse across the plasma membrane.
4. all of the above
5. Milk production
1. is negatively regulated by prolactin.
2. is positively regulated by prolactin.
3. is positively regulated by milk-producing factor.
4. is an unregulated process in new mothers.
6. Thyrotropin-releasing hormone, or TRH,
1. is regulated through a negative feedback mechanism.
2. is regulated through a positive feedback mechanism.
3. is not regulated.
4. none of the above
7. The hormones released by the pancreas
1. are located near the thyroid gland.
2. include insulin and glucose.
3. work together to control the level of glucose in the blood.
4. all of the above
8. Which of the following statements is true concerning the hypothalamus? (1) The hypothalamus is actually part of the brain. (2) The hypothalamus can be considered a link between the nervous and endocrine systems. (3) The hypothalamus releases anti-diuretic hormone. (4) The hypothalamus produces hormones that directly regulate other body processes.
1. 1 only
2. 1 and 2
3. 1, 2, and 3
4. 1, 2, 3, and 4

## Lesson 22.2: Vocabulary I

Name___________________ Class______________ Date________

Match the vocabulary word with the proper definition.

Definitions

_____ 1. hormones that are made of lipids such as phospholipids and cholesterol

_____ 2. releases hormones that increase the rate of metabolism in cells throughout the body

_____ 3. releases hormones that helps keep the level of calcium in the blood within a narrow range

_____ 4. releases fight-or-flight hormones

_____ 5. releases hormones that work together to control the level of glucose in the blood

_____ 6. releases hormones that control sleep-wake cycles and several other processes

_____ 7. the type of cell on which a hormone has an effect

_____ 8. releases sex hormones

_____ 9. messenger molecules released by endocrine glands

_____ 10. a system of glands that release chemical messenger molecules

_____ 11. the master gland of the endocrine system

_____ 12. provides a link between the nervous and endocrine systems

Terms

b. endocrine system

d. hormone

e. hypothalamus

f. pancreas

g. parathyroid glands

h. pineal gland

i. pituitary gland

j. steroid hormones

k. target cell

l. thyroid gland

## Lesson 22.2: Vocabulary II

Name___________________ Class______________ Date________

Fill in the blank with the appropriate term.

1. Most hormones are controlled by a ____________ feedback regulation mechanism.

2. Steroid hormone and their receptors form a complex that influences the expression of ____________.

3. Endocrine hormones travel throughout the body in the ____________.

4. Thyroid hormones increase the rate of ____________ in cells throughout the body.

5. Hormones of the pancreas include ____________ and glucagon.

6. ____________-stimulating hormone stimulates the ovaries to develop mature eggs.

7. The hypothalamus is actually part of the ____________, but it also secretes hormones.

8. Growth hormone stimulates body cells to synthesize proteins and ____________.

9. Most ____________ hormones control other endocrine glands.

10. Endocrine system disorders usually involve the secretion of too much or not enough ____________.

11. The endocrine system is a system of glands that release chemical ____________ molecules into the bloodstream.

12. A ____________ cell is the type of cell on which a hormone has an effect.

## Lesson 22.2: Critical Writing

Name___________________ Class______________ Date________

Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.

Explain how steroid hormones work.

Feb 23, 2012

Feb 20, 2015