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Exam 4 notes - BIOL 2150 EXAM IV NOTES Dr Harmych Section 2...

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BIOL 2150 – EXAM IV NOTES – Dr. Harmych – Section 2 – MW 4:00-5:40 Exam IV Notes Chapter 41 – Animal Hormones Hormones - Chemical signals that have effects on cells in other parts of the body. - Control long term developmental processes. - Endocrine cells - Target cells - Have receptors for a hormone. Chemical Signaling Systems (a) Circulating Hormones Hormones are released into the blood stream and are carried through the body via the blood stream. (b) Local Hormones Paracrine – diffuse from site of release and bind to receptors on nearby cells. They travel locally. Autocrine – bind to receptors on the cells that secrete them. According to Evolutionary History, the endocrine system came before the nervous system. Hormonal Control of Molting - Insects undergo many molts during development. - Instar – growth stage between 2 molts. - Sir Vincent Wigglesworth - Used the bloodsucking bug Rhodnius prolixus for experiments. - Molts 5 times during development. - Each molt is triggered by a blood meal. HYPOTHESIS – Some substance diffusing from the head of Rhodnius prolixus (a blood-sucking bug) controls molting. Experiment 1 CONCLUSION – Whether a decapitated Rhodnius prolixus will molt depends on the interval between a blood meal and the decapitation, which supports the idea that a substance must pass from head to body. Page 1
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BIOL 2150 – EXAM IV NOTES – Dr. Harmych – Section 2 – MW 4:00-5:40 Experiment 2 CONCLUSION – A diffusible substance is necessary for molting. Two Hormones Control Molting - Prothoracicotropic hormone (PTTH) - Brain hormone - Produced by brain cells and stored in the corpora cardiaca . - Released after a blood meal. - Ecdysone - Produced in the prothoracic gland . -Stimulates molting. Juvenile Hormone - Controls development in juveniles. - Prevents maturation. - All decapitated bugs molted directly into adults. - Experiment 3 - Partial decapitation results in bugs that molt into juvenile stages. - Juvenile hormone is stored in corpora allata located in the back of the head. Complete Metamorphosis - Larvae do not look like adult organism. - Pupa - Presence of juvenile hormone prevents development into the pupa and eventually an adult. Juvenile Hormone and Insect Control - Synthetic forms are used in insect control. - Problems? - Bad bugs - Vertebrates Chemical Classification of Hormones - Peptide Hormones - Water soluble, easy transport in the blood - Insulin Page 2
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BIOL 2150 – EXAM IV NOTES – Dr. Harmych – Section 2 – MW 4:00-5:40 - Steroid hormones - Derivatives of cholesterol - Testosterone, estrogen - Amine Hormones - Derivatives of the amino acid tyrosine - Thyroxin Hormone Receptors - Can be on the outside or inside of a cell. - Lipid-soluble hormones - Receptors on the inside of cell - Many effect gene expression - Water-soluble hormones - Receptors are on the cell surface.
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