The_Endocrine_System.ppt - The Endocrine System Endocrinology the study of hormones The body adapts to changing conditions in two ways Quick(in

The_Endocrine_System.ppt - The Endocrine System...

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The Endocrine SystemEndocrinology– the study of hormonesThe body adapts to changing conditions in two ways:Quick (in milliseconds) short term response by the nervous system (electrical and chemical)Slower (in minutes to hours) long term response by the endocrine system (chemical messengers)Some endocrine responses aid in maintaining homeostasis (control of blood sugar, calcium ion levels, and metabolism)Others cause permanent structural changes (growth and development)
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The Endocrine SystemExocrine glandssecrete their product through ducts to specific locationsEndocrine glandssecrete their product into the bloodstream. These secretions called hormones(“to set in motion”), are chemical compounds that affect the activities of other cells by instructing the cell to produce specific structural (fibrous) and functional (globular) proteins.
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Types of HormonesCirculating hormonesor endocrinesenter the blood stream and act on distant target cells. Local hormones: Paracrinesare hormones that act on neighboring cells; Autocrinesare hormones that act upon the same cell that secretes them.
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HormonesMost hormones are composed of amino acidsthat range in size from single amino acid hormones called biogenic amines(histidine to histamine) to large protein hormonesapproximately 3 to 200 amino acids long. Most endocrine organs, other than the reproductive organs (ovaries, testes, and placenta) and the outer portion of the adrenal glands, secrete amino acid based hormones.
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HormonesLipid based hormonesinclude steroid hormones and eicosinoids, which are derivatives of arachadonic acid (i.e. prostaglandins).Steroidhormones are built from molecules of cholesterol and are released by the reproductive organs and the adrenal cortexProstaglandinsare produced by fatty acids by most tissues of the body. Locally, prostaglandins coordinate cellular activities within the tissue. Some prostaglandins enter the bloodstream and have a more widespread effect on body processes.
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Action on CellsEach hormone has specific target cellsthat respond to its presence. These target cells have the appropriate receptor moleculesin their cell membranes. All the structures and functions of cells depend on proteins. Structural proteins determine the general shape and internal structure of a cell, and enzymes (proteins) control its metabolic activities. Hormones alter the workings of a cell by changing the dominant types, activities, or quantities of important enzymes and structural proteins.
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Action on CellsSome hormones (insulin, thyroid hormones) affect many tissues, others, like TSH, are very specific.Some hormones are effective for long periods of time (thyroid hormones act for about 2 weeks) and others act rapidly and are removed rapidly (ADH – 15 min.)
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Control of Hormone SecretionHormone secretion varies from hour to hour and from day to day.
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