endocrine system

endocrine system - Lecture #3 Endocrine System 27/06/2008...

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Unformatted text preview: Lecture #3 Endocrine System 27/06/2008 12:03:00 I.Endocrine Vs. Exocrine A. Endocrine Horones Bloodstream Ductless B. Exocrine Special body fluids (sweat, tears, saliva, bile, enzymes, mucus, breast milk) Cavity/surface Ducts Paracrine : chemical signal diffuses across the extracellular fluid ( ECF) between nearby cells autocrine : chemical signal feeds back on signaling cell (gastrin) II. Signal transduction A. Receptors 1.intracellular receptors o Located inside cell o Hydrophobic chemical messengers 2. ligand-gated ion channels o Allow specific ion through in response to ligand binding change in permeability of membrane 3. Receptor enzymes o Activate or inactivate intracellular enzymes (cells talking to eachother) via phosphorylation cascades (add phosphate to an enzyme) proteins at each step phosphorylate or dephosphorylate other proteins signal amplification 4. G-protein coupled receptors: receptor interacts with G protein (figure 1) pip-ca2+ signal transduction pathway o also uses G-protein o 2 nd messengers: IP3 +DAG ~ cause increase in intracellular (Ca2+) third messenger ~Ca2+ as major intracellular signaler III. Hormones= substances secreted by specialized cells (endocrine glands) that travels in the blood and causes a reaction in target cells Active at very low concentrations Involved in regulation (homeostasis), also development and behavior A. Peptide Amino acids (cant cross membrane by itself~ hydrophillic) Uses extracellular receptors (talk to outside of cell) G-protein/2 nd messenger Rapid effects Modify enzyme activity temporary B. Steroids Cholesterol (hydrophobic) Use intracellular receptors ~ pass right on through...
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endocrine system - Lecture #3 Endocrine System 27/06/2008...

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