3. Diabetes involves defects in the glucose feedback loop moderated by which hormone?

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1 Topic 3: Does Ben Have Diabetes? 1. Review the introduction, what you will learn, and your task. 2. Click the forward arrow button. 3. What is the role of each hormone in the regulation of blood glucose levels? Glucagon? Insulin? 3. Diabetes involves defects in the glucose feedback loop moderated by which hormone? 4. What are the two major causes of type 2 diabetes? 5. What is Ben s diagnosis? 6. Which best explained Ben s condition? 7. Click the play button to begin the animation. The animation represents what happens in a normal person after drinking a sugary drink for the glucose tolerance test. 8. What is the stimulus? 9. What detects the stimulus? 10. How does the control center respond? 11. What is the signal? 12. What are the effectors? 13. What response does the signal trigger in the effectors? 14. What is the response (feedback)? 15. How is the feedback loop for a normal response modified in someone with decrease insulin sensitivity (impaired glucose tolerance)? 16. How is the feedback loop for a normal response modified in someone with the failure of the insulin secreting B- cells? 17. Does Ben have diabetes? 18. Does Ben need to take insulin? 19. Does Ben need to take any other drugs? 20. Does Ben have to stop eating sweets and drinking soda?

2 Part 2: Questions 1. The diagram below represents the feedback loop involved in controlling blood sugar levels in the human body. Study the diagram and use it to answer the questions in this a. What is the stimulus? b. What detects the stimulus? c. What is the control center? d. What is the signal? e. What is/are the effector(s)? f. What is the response (feedback)? g. Was homeostasis restored? h. 2. The diagram below represents the feedback loop involved in controlling blood calcium levels in the human body. Study the diagram and use it to answer the questions in this section. a. What is the stimulus? b. What detects the stimulus? c. What is the control center? d. What is the signal? e. What is/are the effector(s)? f. What are the responses (feedback)? g. Was homeostasis restored? h.

3 4. The diagram below represents the feedback loop during blood clotting. Study the diagram and use it to answer the questions in this section. a. What is the initial stimulus? b. What is the control center? c. What are the signals? d. e. Was homeostasis restored? f. g. When would this feedback loop eventually stop? 5. Identify each of the following as an example of Positive or Negative feedback. Use the key below to indicate your answers. P. Positive N. Negative Response is opposite of or counters the stimulus Response amplifies or reinforces the stimulus Continues to disrupt homeostasis Restores homeostasis When blood ph levels fall below a set point, the kidneys collect and remove more H+ (hydrogen ions) from the blood, thus bring the blood ph levels back to normal The female hormone estrogen triggers the release of the luteinizing hormone (LH); increased production of LH increases the production and release of estrogen When blood calcium levels rise above a set point (hypercalcemia) specialized cells in the thyroid secrete a hormone called calcitonin. Calcitonin causes specialized cells in bone tissue to take calcium out of the blood and store it in bone tissue. When body temperature rises above a set point, the hypothalamus directs sweat glands in the skin to release sweat. As the sweat evaporates from the skin, heat is removed from the body. As heat is removed, body temperature returns to normal

4 6. A baby begins to nurse her mother's breast and a few drops of milk are released. This encourages the baby and releases a hormone in the mother which further stimulates the release of milk. The hungry baby continues to nurse, stimulating more milk release until she stops. 7. An example of homeostasis in cells is the phenomenon called contact inhibition, in which division in a population of cells stops when they become so numerous that they touch each other. It is believed that, a chemical "messenger" that inhibits further cell division is passed from cell to cell. In contrast, cultured, or artificially produced, cancer cells continue dividing even after cells touch. Thus, cancer cells appear to have lost the homeostatic mechanism of contact inhibition. What is the response of normal cells? What is the response of cancer cells? 8. Homeostatic mechanisms also operate to regulate the size of populations. An example is the relationship between the populations of predatory animals and their prey. If prey become abundant, so do their predators, until predation diminishes the supply of prey and causes a decline in the predator population. This allows the prey population to build up again, and the cycle is repeated. In this manner, the populations of both kinds of animals oscillate around a mean.

5 9. When the sun rises, blue-light receptors in plant cells trigger the uptake of K+ by guard cells. Guard cells surround stomata. As the guard cells take in K+ the water potential inside the cells decreases and water enters the cells. As water enters the guard cells the cells swell and curve opening the stomata. Open stomata allow CO2 to enter the leaf and O2 to exit. 10. The bicarbonate buffer system is the major buffer system at work in the blood. It helps to maintain blood ph within a very narrow range (7.35 to 7.45). The equation below represents this buffer system. CO 2 + H 2 O H 2 CO 3 HCO H + A person hyperventilates (blows off too much CO2). How do you know

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