Exam 4 Study Guide 2003

Exam 4 Study Guide 2003 - Chapter45...

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Chapter 45 How do hormones affect insect molting? Brain hormone stimulates release of ecdysone from prothoracic glands. Juvenile hormone (JH) promotes retention of larval characteristics. Ecdysone promotes molting (in presence of juvenile hormone) of adult characteristics. 1. Neurosecretory cells produce PTTH and is stored in the corpus allatum. 2. PTTH signals prothoracic gland to secrete ecdysone. 3. Each episodic secretion of ecdysone stimulates a molt 4. JH determines result of molt. (High JH levels produces another larval stage because JH suppresses metamorphosis)(Low JH means pupa forms and then adult insect) What are the reasons for getting hyper versus hypothyroid goiter?  A goiter is an enlarged thyroid gland associated with hypo or hyper levels of thyroxine. Hyperthyroidism: Too low secretion of thyroid hormones to properly regulate metabolism. Hyperthyroid goiter results when the negative feedback mechanism fails, even though blood levels of thyroxine are high. Commonly caused by autoimmune disease in which an antibody to the TSH receptor is produced. The antibody binds to the TSH receptor causing thyroid cells to release excess thyroxine (Graves’ Disease). Thyroid stays max active and grows larger causing high metabolic rates. Hypothyroidism: This is the condition where there is insufficient thyroxine to turn off TSH production. Usually caused by iodine deficiency. When TSH levels are high the thyroid keeps making nonfunctional thyroxine and gets larger. Symptoms are low metabolism, cold intolerance and mental sluggishness.
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What are the specific hormones needed to maintain Calcium homeostasis, sugar homeostasis,  and that respond to stress (long term and short term). How do they work? Control of Blood Calcium : two antagonistic hormones regulate (calcitonin/PTH) 1. Parathyroid hormone (PTH): released by the parathyroid glands a. If Ca++ level falls, parathyroid glands releases PTH with 3 targets (bone, kidney, intestines) b. Osteoclasts break down bone and release calcium c. PTH also promotes Ca++ resorption by kidneys to prevent loss in urine; also increases elimination of phosphate to reduce calcium phosphate salt precipitation (stones) d. Promotes vitamin D activation and stimulates gut to absorb Ca++ from food e. Vitamin D acts in negative feedback loop to inhibit transcription of PTH gene 2. Calcitonin: released by the thyroid gland a. Thyroid releases calcitonin if Ca++ gets too high in blood. Takes Ca++ from blood and makes more bone b. Osteoblasts use circulating calcium to build new bone. Control of Sugar homeostasis: two antagonistic hormones regulate (insulin / glucagon) Cells produced in Pancreas: a. Beta cells produce and secrete insulin (islets of Langerhans) b. Alpha cells produce and secrete glucagon c. Delta cells produce somatostatin 1. After mean glucose levels rise and stimulate Beta cells to release insulin 2. Insulin stimulates cells to use glucose and convert it to glycogen and fat
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3. When glucose levels fall, pancreas stops releasing insulin and cells switch to using glycogen
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Exam 4 Study Guide 2003 - Chapter45...

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