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ch18ppt - 18-1Chapter 18The Endocrine System•Endocrine...

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Unformatted text preview: 18-1Chapter 18The Endocrine System•Endocrine and nervous systems work together•Endocrine system–hormones released into the bloodstream travel throughout the body–results may take hours, but last longer•Nervous system–certain parts release hormones into blood–rest releases neurotransmitters excite or inhibit nerve, muscle & gland cells–results in milliseconds, brief duration of effects18-2General Functions of Hormones•Help regulate:–extracellular fluid–metabolism–biological clock–contraction of cardiac & smooth muscle–glandular secretion–some immune functions•Growth & development•Reproduction18-3Endocrine Glands Defined•Exocrine glands–secrete products into ducts which empty into body cavities or body surface–sweat, oil, mucous, & digestive glands•Endocrine glands–secrete products (hormones) into bloodstream–pituitary, thyroid, parathyroid, adrenal, pineal–other organs secrete hormones as a 2nd function•hypothalamus, thymus, pancreas,ovaries,testes, kidneys, stomach, liver, small intestine, skin, heart & placenta18-4Hormone Receptors•Hormones only affect target cells with specific membrane proteins called receptors18-5Role of Hormone Receptors•Constantly being synthesized & broken down•A range of 2000-100,000 receptors / target cell•Down-regulation–excess hormone, produces a decrease in number of receptors•receptors undergo endocytosis and are degraded–decreases sensitivity of target cell to hormone•Up-regulation–deficiency of hormone, produces an increase in the number of receptors–target tissue more sensitive to the hormone18-6Blocking Hormone Receptors•Synthetic hormones that block receptors for naturally occurring hormones–RU486 (mifepristone) binds to the receptors for progesterone preventing it from maintaining the uterus in a pregnant woman•used to induce abortion•brings on menstrual cycle•Hormone is prevented from interacting with its receptors and can not perform its normal functions18-7Circulating & Local Hormones•Circulating hormones–act on distant targets–travel in blood•Local hormones–paracrines act on neighboring cells–autocrines act on same cell that secreted them18-8Lipid-soluble Hormones•Steroids–lipids derived from cholesterol on SER–different functional groups attached to core of structure provide uniqueness•Thyroid hormones–tyrosine ring plus attached iodines are lipid-soluble•Nitric oxide is gas18-9Water-soluble Hormones•Amine, peptide and protein hormones–modified amino acids or amino acids put together–serotonin, melatonin, histamine, epinephrine–some glycoproteins•Eicosanoids–derived from arachidonic acid (fatty acid)–prostaglandins or leukotrienes18-10Hormone Transport in Blood•Protein hormones circulate in free form in blood•Steroid (lipid) & thyroid hormones must attach to transport proteins synthesized by liver–improve transport by making them water-soluble–slow loss of hormone by filtration within kidney...
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ch18ppt - 18-1Chapter 18The Endocrine System•Endocrine...

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