chapter17

chapter17 - Endocrine System Has specialized tissues =...

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Endocrine System Has specialized tissues = endocrine glands Form system for homeostasis Secrete hormones into blood Hormones Travel in blood signal different target cells = chem. messenger Not connected anatomically Specific target cells for each Have receptors (membrane bound proteins) that uniquely bind to specific hormone Endocrine System Fnx: 1. Homeostasis (regulate metabolism + H 2 2. Deal with stress 3. Growth 4. Control Reproduction 5. Regulate RBC production 6. Circulation, digestion, absorption Some Glands Control Other Glands Some glands tropic hormones signal other glands to secrete hormones Complexity of Endocrine System 1 gland makes multiple hormones w/ diff target tissues + actions (Pancreas) A signal hormone can have many target cells multiple effects (Eph) Single target cell can be influence my 1+ hormone (liver/storage + release of glucose) Hormone secretion rate varies over time Same chem. messenger can be hormone OR NT (NePH) Hormone Classifications 1. Peptides = shorter protein chains (majority) [H 2 O soluble] 2. Amines = from aa tytosine [H 2 O soluble] Secreted by adrenal medulla 3. Steroids = from fats/cholesterol (sex hormones) [fat soluble] How Hormones Act 1. Bind w/ membrane protein receptors alters permeability allows substances into cell (insulin + glucose action) 2. Steroid hormones diffuse through membrane react w/ something inside change cell activity 3. Lipophilic hormones activate intracellular genes creates new intracellular proteins Hormones (Usually) Produce Longer Lasting Response Effects can last seconds, hours, or days What Happens to Hormones After Release? Most deactivate by membrane bound or intracellular enzymes Some excreted through urine Others reabsorbed by original gland Methods Used to Induce Glandular Secretion 1. Negative Feedback (most common) Seeks to control a variable w/in very narrow range Uses controllable substances to inc/dec hormone release 2. Neuro-Endocrine Reflexes (ie. Adrenal Glands)
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chapter17 - Endocrine System Has specialized tissues =...

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