ch18ppt - 18-1Chapter 18The Endocrine SystemEndocrine and...

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Unformatted text preview: 18-1Chapter 18The Endocrine SystemEndocrine and nervous systems work togetherEndocrine systemhormones released into the bloodstream travel throughout the bodyresults may take hours, but last longerNervous systemcertain parts release hormones into bloodrest releases neurotransmitters excite or inhibit nerve, muscle & gland cellsresults in milliseconds, brief duration of effects18-2General Functions of HormonesHelp regulate:extracellular fluidmetabolismbiological clockcontraction of cardiac & smooth muscleglandular secretionsome immune functionsGrowth & developmentReproduction18-3Endocrine Glands DefinedExocrine glandssecrete products into ducts which empty into body cavities or body surfacesweat, oil, mucous, & digestive glandsEndocrine glandssecrete products (hormones) into bloodstreampituitary, thyroid, parathyroid, adrenal, pinealother organs secrete hormones as a 2nd functionhypothalamus, thymus, pancreas,ovaries,testes, kidneys, stomach, liver, small intestine, skin, heart & placenta18-4Hormone ReceptorsHormones only affect target cells with specific membrane proteins called receptors18-5Role of Hormone ReceptorsConstantly being synthesized & broken downA range of 2000-100,000 receptors / target cellDown-regulationexcess hormone, produces a decrease in number of receptorsreceptors undergo endocytosis and are degradeddecreases sensitivity of target cell to hormoneUp-regulationdeficiency of hormone, produces an increase in the number of receptorstarget tissue more sensitive to the hormone18-6Blocking Hormone ReceptorsSynthetic hormones that block receptors for naturally occurring hormonesRU486 (mifepristone) binds to the receptors for progesterone preventing it from maintaining the uterus in a pregnant womanused to induce abortionbrings on menstrual cycleHormone is prevented from interacting with its receptors and can not perform its normal functions18-7Circulating & Local HormonesCirculating hormonesact on distant targetstravel in bloodLocal hormonesparacrines act on neighboring cellsautocrines act on same cell that secreted them18-8Lipid-soluble HormonesSteroidslipids derived from cholesterol on SERdifferent functional groups attached to core of structure provide uniquenessThyroid hormonestyrosine ring plus attached iodines are lipid-solubleNitric oxide is gas18-9Water-soluble HormonesAmine, peptide and protein hormonesmodified amino acids or amino acids put togetherserotonin, melatonin, histamine, epinephrinesome glycoproteinsEicosanoidsderived from arachidonic acid (fatty acid)prostaglandins or leukotrienes18-10Hormone Transport in BloodProtein hormones circulate in free form in bloodSteroid (lipid) & thyroid hormones must attach to transport proteins synthesized by liverimprove transport by making them water-solubleslow loss of hormone by filtration within kidney...
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This note was uploaded on 05/23/2010 for the course BIO 222 taught by Professor Brooks during the Spring '10 term at Prairie State College .

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ch18ppt - 18-1Chapter 18The Endocrine SystemEndocrine and...

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