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Published byBruno Burns Modified over 9 years ago
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Pages 309-312
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Hormones are chemical messengers Three classifications: Two main groups: 1. Amino acid–based: Proteins Peptides (chains of amino acids; smaller than proteins) Amines (a derivative of ammonia) 2. Steroids—made from cholesterol (lipid based) Local Hormones: 3. Prostaglandins— made from highly active lipids that are released from almost all cell membranes © 2015 Pearson Education, Inc.
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Hormones are specific Target a cell or organ Target cells must have specific protein receptors Hormone binding alters cellular activity The act of a hormone binding to its target cell is very similar to that of an enzyme and its substrate- like a lock and key mechanism © 2015 Pearson Education, Inc.
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Hormones can cause: 1. Changes in membrane permeability or electrical state 2. Synthesis of proteins, such as enzymes 3. Activation or inactivation of enzymes 4. Stimulation of mitosis 5. Promotion of secretory activity © 2015 Pearson Education, Inc.
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The chemical structure of a hormone determines how it is delivered to its target Two mechanisms: 1. Direct gene activation Steroids Ex: hormones of the adrenal cortex: corticosteroids 2. Indirect delivery: Second-messenger system (a middle man) 1. Water soluble, non-steroids (protein/peptide hormones) © 2015 Pearson Education, Inc.
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1. Diffuse directly through cell membrane 2. Enter the nucleus 3. Bind to a receptor protein within the nucleus 4. This hormone-receptor complex binds to specific sites on the cell’s DNA 5. Certain genes are activated to synthesize new proteins http://highered.mheducation.com/sites/0072943696/student_view0/chapter 10/animation__mechanism_of_steroid_hormone_action__quiz_1_.html © 2015 Pearson Education, Inc.
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Steroid hormone Cytoplasm Nucleus Receptor protein Hormone-receptor complex DNA mRNA New protein Plasma membrane of target cell 1 (a) Steroid hormone action 2 3 4 5 6 Slide 1
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1. Hormone (first messenger) binds to a membrane receptor 2. Activated receptor sets off a series of reactions that activates an enzyme 3. Enzyme catalyzes a reaction to produce a second messenger 4. Second messenger manage additional intracellular changes to promote a specific response in the target cell https://www.youtube.com/watch?v=Nt2r5R0ZO5U © 2015 Pearson Education, Inc.
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(b) Nonsteroid hormone action Plasma membrane of target cell Receptor protein Nonsteroid hormone (first messenger) Cytoplasm Enzyme ATP cAMP Second messenger Effect on cellular function, such as glycogen breakdown 1 2 3 4 Slide 1
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Three mechanisms for stimulus of glands: 1. Hormonal (most common) Endocrine organs are activated by other hormones Ex: anterior pituitary secretes hormones that stimulate other glands to release hormones 2. Humoral Changing blood levels of certain ions and nutrients stimulate hormone release Ex: PTH/calcitonin released in response to Ca ⁺⁺ levels 3. Neural Nerve impulses stimulate hormone release Ex: sympathetic division stimulates release of epinephrine/norepinehprine by the adrenal medulla © 2015 Pearson Education, Inc.
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Hormonal Communication http://highered.mheducation.com/sites/0072495855/student_view0/ chapter20/animation__hormonal_communication.html http://highered.mheducation.com/sites/0072495855/student_view0/ chapter20/animation__hormonal_communication.html Hormone function summarized with animation for both chemical types of hormones https://www.youtube.com/watch?v=TgNwxF3aQpE https://www.youtube.com/watch?v=TgNwxF3aQpE
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