AnswerKeyPracticeMT2

AnswerKeyPracticeMT2 - ANSWER KEY Practice Midterm II 1. If...

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ANSWER KEY Practice Midterm II 1. If a cancerous human thyroid is removed surgically, it is important to determine if any thyroid cells remain. In one method, the doctor feeds the patient radioactive iodine. The radioactivity becomes concentrated in the thyroid, enough so to generate an image of the thyroid on film. a. Why is iodine concentrated in the thyroid (10 pts)? Iodine would be concentrated in the thyroid because it is used for production of the thyroid hormones T3 and T4. To enhance the detection of any thyroid cells remaining, doctors sometimes inject thyrotropin a few days before the patient is given radioactive iodine. b. What is another name for thyrotropin and what is the normal role of this substance in the body (10 pts)? Thyrotropin is also known as thyroid stimulating hormone or TSH. It stimulates the thyroid to synthesize and release T3 and T4. c. What organ normally produces thyrotropin and how is thyrotropin production or release regulated (15 pts)? The anterior pituitary normally releases thyrotropin. Release of thyrotropin is stimulated by thyrotropin-releasing hormone (TRH), which is secreted by the hypothalamus. Thyrotropin and TRH levels are also regulated by negative feed back loops from T3 and T4. d. Why would thyrotropin injection increase the amount of iodine concentrated in thyroid cells (15 pts)? Increased levels of thyrotropin increase the production of T3 and T4, which increases the concentration of iodine in the thyroid. 2. IVF (in vitro fertilization) is a method of assisted reproduction. In one type of IVF, an egg is collected surgically just before it would normally be released from the ovary; sperm are collected from the man as they are released from the body (ejaculated). The sperm and the egg are then combined in a laboratory dish, where fertilization occurs. Soon thereafter an embryo, consisting of two to four cells, is transferred in fluid through the cervix to the woman's uterus. a. Every one of the listed events must be timed to the woman's hormonal cycle. Explain why this coordination is important (and why the man's hormones levels are ignored). (20 pts) The coordination of these events must be timed to the female hormone cycle because the hormone levels trigger a cycle of sequential events: the development of the follicle, the buildup of the endometrium, the release of the egg, and the loss of the endometrium. The egg must be collected at the correct time. A mature egg and mature sperm are both needed; male hormone levels can be ignored because males are continuously producing sperm.
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This note was uploaded on 05/20/2008 for the course BILD 1 taught by Professor Boulanger during the Spring '08 term at UCSD.

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AnswerKeyPracticeMT2 - ANSWER KEY Practice Midterm II 1. If...

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