Module 2 The Endocrine System

1.2.4 page 4

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Antagonistic Hormones Regulate Calcium Levels

 

Two antagonistic hormones, which are hormones that work in opposition to one another to establish overall balance or homeostasis, regulate calcium levels in the blood. One of these hormones, calcitonin, originates from the thyroid gland, and the other, parathyroid hormone, from the parathyroid glands. To gain an understanding of where these hormones are secreted, how they function to maintain calcium homeostasis, how their secretion is regulated, and what happens when calcium balance is disrupted, research and answer the following questions in Try This #3. As in Try This #2, the completed answers to these questions can become your notes for this part of Lesson 4. Where appropriate, answer in complete sentences. You may use library sources, the Internet, page 449 in your textbook, or any other resources to which you have access that will help you complete the questions. When you have finished the questions, check your answers and file your work in your course folder. Seek help from your instructor to explain any difficulty that you may have encountered.

 

Try This

TR 3.

1. Describe at least three functions of calcium in the body.
2. Calcium homeostasis is mainly regulated by two hormones. Identify the two hormones and the glands that produce each of them.
3. The two hormones that you identified in Question #2 are described as being antagonistic hormones. Define what is meant by this.
4. Describe the mechanism of calcitonin function.
5. Outline the regulation of blood calcium levels by calcitonin.

Use the following additional information to answer the next four questions.

 

FMEN 1 patients often develop minute tumors in the parathyroid glands. This happened to Emily. Consequently her parathyroid glands over-secrete parathyroid hormone.

6. Describe the overall effect of parathyroid hormone. Outline three specific actions on the body caused by this hormone to achieve its overall effect.
7. 
   © Troy Kellogg/shutterstock
   Emily had fallen on a very icy sidewalk and had broken some bones in her wrist. The bones were reset, but months later they still had not healed. During this time Emily landed in the emergency room of the hospital with severe abdominal pain which was diagnosed as a case of kidney stones. Construct a hypothesis that may explain the underlying cause of both health problems. (Remember, a hypothesis should be in the form of an “If … Then … Because …” statement.)

8. Draw a negative feedback loop that illustrates the regulation of blood calcium levels by parathyroid hormone.

9. How would Emily’s feedback loop be different?

 

Self-Check

Do the following Self Check, which consists of some multiple choice questions and a couple of numerical response questions, in preparation for completing the lesson assessment. Check your answers and, if you do not understand any of the concepts, be sure to discuss these with your instructor. The Diploma exam will be composed of questions that are similar in style to the following questions. It is a good idea to practice these types of questions as much as possible.

 

Use the following diagram to answer the next two questions.

 

1. Which endocrine gland shown in this illustration would be directly responsible for the development of bone thinning if it was overproducing its hormones?
   
   
   1. 2
   2. 3
   3. 4
   4. 6
2. Cretinism can develop if low secretions of hormone are produced by the gland labeled
   
   
   1. 2
   2. 3
   3. 4
   4. Both 2 and 4
3. Hypothyroidism that developed in childhood would be characterized by
   
   
   1. impaired physical and mental development
   2. thirst and consumption of large volumes of water
   3. increased blood pressure and increased heart rate
   4. suppression of the immune system and the development of goiter
4. The area of the brain that normally initiates the secretion of TSH is the
   
   
   1. medulla oblongata
   2. cerebrum
   3. pons
   4. hypothalamus
5. A condition that results in an enlargement of the thyroid gland may be caused by a diet deficient in
   
   
   1. salt
   2. iron
   3. iodine
   4. sodium

Use the following information to answer the next three questions.

 

Vegetables such as cabbage, rutabaga, and turnips contain goitrin, a substance that inhibits iodine uptake by the body.

6. A person with a diet high in vegetables containing goitrin may gain weight fairly rapidly. A possible explanation for this weight gain would be
   
   
   1. increased protein metabolism
   2. decreased blood sugar levels
   3. increased glycogen release
   4. decreased metabolic rate
7. The function of which gland would be most affected by goitrin?
   
   
   1. anterior pituitary
   2. adrenal cortex
   3. thyroid gland
   4. parathyroid gland
8. An increase in goitrin consumption would likely cause a person to experience increased
   
   
   1. fatigue
   2. heart rate
   3. breathing rate
   4. blood pressure

Use the following information to answer the next two questions.

 

On April 26, 1986, a major accident occurred at a nuclear generating station in Chernobyl. The nuclear explosion dispersed several tons of radioactive iodine, cesium, uranium, and other elements five kilometers into the air.

 

Radioactivity is extremely damaging to living cells.

From Biosphere 2000: Protecting Our Global Environment

9. As soon as people in Europe realized there had been a nuclear accident, they rushed to buy iodine tablets. What reason would people have for consuming large quantities of iodine?
   
   
   1. So that iodine from the tablets, instead of the radioactive iodine, would accumulate in the thyroid
   2. Because iodine, by negative feedback, blocks the formation of TSH, therefore protecting the thyroid from radioactivity
   3. Because iodine inhibits cell division, thereby reducing the amount of cellular damage occurring during exposure to radiation
   4. So that iodine from the tablets could accumulate in the hypothalamus and block radioactivity from killing/altering body cells
10. In addition to symptoms of radiation poisoning, which symptoms would be expected among people who did not take iodine tablets?
    
    
    1. Pancreatic dysfunction and insufficient insulin production
    2. Metabolic dysfunction resulting in fatigue and weight gain
    3. Increased ACTH secretion and puffiness of face, chest, and abdomen
    4. Pituitary dysfunction resulting in increased hGH secretion and development of gigantism

Use the following information to answer the next question.

 

Some Glands and Hormones of the Human Body

 

 

Numerical Response

11. Select a set of numbers for glands and hormones that correctly completes the statement below.
    
    The ______ secretes ______ which stimulates the ______ to produce ______,
          (gland)             (hormone)                          (gland)                (hormone)
    
    which regulates metabolism (cellular respiration).

Numerical Response

 

Use the following information to answer the next question.

 

Endocrine Glands

1. adrenal medulla
2. anterior pituitary
3. posterior pituitary
4. thyroid
5. parathyroid gland
6. adrenal cortex

12. Using the numbers that represent the endocrine glands shown above, match the hormone below to the endocrine gland that produces it.

Endocrine Gland:          ________                  ______           ______           _______
Hormone:                   Thyroxine                    PTH                TSH                Calcitonin