L20 NPB 101 - Lecture 20 •  SmartSite: – ...

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Unformatted text preview: Lecture 20 •  SmartSite: –  Lecture 20 Notes •  Review –  Endocrinology IntroducAon •  Announcements: –  Grades available this weekend •  Endocrinology –  IntroducAon –  Neuroendocrine –  Growth Hormone •  Reading (Recommended): –  Relevant porAons Chapter 4 & 18 1 REV: Hormones Table 4 ­4, pg. 118 2 (More) Mechanism of AcAon of Hydrophilic Hormones Fig. 4 ­25, pg. 123 3 Signal AmplificaAon Fig. 4 ­26, pg. 126 4 Mechanism of AcAon of Lipophilic Hormones •  Effects are generally slower onset, longer lasAng than effects via membrane receptors •  Examples: –  Estrogen induces genes inducing growth of uterus, mammary glands –  Thyroid hormone induces genes involved in cerebellar Purkinje cell differenAaAon, axon myelinaAon 5 Fig. 4 ­27, pg. 127 Hormone Influence at Target Cell •  Hormone can influence acAvity of another hormone at given target cell in one of three ways –  Permissiveness •  One hormone must be present in adequate amounts for full exerAon of another hormone’s effect •  O`en by increasing second hormone’s receptors –  Synergism •  Occurs when acAons of several hormones are complimentary •  Combined effect is greater than the sum of their separate effects –  Antagonism •  Reduces effecAveness of second hormone •  O`en by decreasing the second hormone’s receptors, or down ­ stream signaling 6 Causes of Endocrine Disorders Table 18 ­1, pg. 665 7 Neuroendocrine 8 Pituitary Gland •  Hypophysis •  Small gland located in bony cavity just below hypothalamus •  Consists of two anatomically and funcAonally disAnct lobes –  Posterior pituitary (neurohypophysis) –  Thin stalk connects pituitary gland to hypothalamus •  Composed of nervous Assue –  Anterior pituitary (adenohypophysis) •  Consists of glandular epithelial Assue 9 Fig. 18 ­4, pg. 670 Pituitary Gland •  Release of hormones from both anterior and posterior pituitary is controlled by hypothalamus •  Posterior pituitary –  Along with hypothalamus forms neuroendocrine system –  Does not actually produce any hormones –  Stores and releases two small pepAde hormones •  Vasopressin •  Oxytocin –  Conserves water during urine formaAon –  SAmulates uterine contracAon during childbirth and milk ejecAon during breast ­feeding 10 Hypothalamus & Posterior Pituitary Fig. 18 ­5, pg. 671 11 Anterior Pituitary •  Anterior Pituitary •  Secretes six different pepAde hormones that it produces itself –  Tropic hormones •  Thyroid ­sAmulaAng hormone (TSH) –  SAmulates secreAon of thyroid hormone –  SAmulates secreAon of corAsol by adrenal cortex –  In females, sAmulates growth and development of ovarian follicles; promotes secreAon of estrogen by ovaries –  In males, required for sperm producAon –  In females, responsible for ovulaAon and luteinizaAon; regulates ovarian secreAon of female sex hormones –  In males, sAmulates testosterone secreAon –  Primary hormone responsible for regulaAng overall body growth; important in intermediary metabolism •  AdrenocorAcotropic hormone (ACTH) •  Follicle ­sAmulaAng hormone (FSH) •  Luteinizing hormone (LH) •  Growth hormone (GH) –  Not a tropic hormone •  ProlacAn (PRL) –  Enhances breast development and milk producAon in females 12 Vascular Link Between the Hypothalamus and Anterior Pituitary Median eminence Fig. 18 ­8, pg. 676 13 Anterior Pituitary Hormones Fig. 18 ­6, pg. 673 14 Major Hypophysiotropic Hormones •  SecreAon of each anterior pituitary hormone is sAmulated or inhibited by one or more hypothalamic hypophysiotropic hormones Table 18 ­4, pg. 674 15 NegaAve Feedback in Endocrine Control •  Anterior pituitary hormone secreAon controlled by: –  Hypothalamic releasing and inhibiAng hormones –  Feedback by target ­ gland hormones Fig. 18 ­7, pg. 675 16 Endocrine Control of Growth •  Growth depends on growth hormone but is influenced by other factors as well –  GeneAc determinaAon of an individual’s maximum growth capacity –  An adequate diet –  Freedom from chronic disease and stressful environmental condiAons –  Normal levels of growth ­influencing hormones 17 Growth Rate •  Not conAnuous •  Factors responsible for promoAng growth are not the same throughout growth period •  Fetal growth –  Promoted largely by hormones from placenta –  GH plays no role in fetal development •  Postnatal growth spurt •  Pubertal growth spurt Fig. 18 ­9, pg. 678 –  Displayed during first two years of life –  Occurs during adolescence 18 Growth Hormone •  Primarily promotes growth indirectly by sAmulaAng liver’s producAon of somatomedins –  Primary somatomedin is insulin ­like growth factor (IGF ­1) •  Exerts metabolic effects not related to growth –  Increases fafy acid levels in blood by enhancing breakdown of triglyceride fat stored in adipose Assue –  Increases blood glucose levels by decreasing glucose uptake by muscles Fig. 18 ­11, pg. 681 19 •  Acts directly on bone and so` Assues to bring about most growth ­promoAng acAons •  SAmulates protein synthesis, cell division, and lengthening and thickening of bones Growth •  Other hormones besides growth hormone are essenAal for normal growth –  Thyroid hormone –  Insulin •  Growth severely stunted in hypothyroid children •  HypersecreAon does not cause excessive growth •  Deficiency o`en blocks growth •  Hyperinsulinism o`en spurs excessive growth •  Play role in pubertal growth spurt, sAmulate protein synthesis in many organs •  Effects depend on presence of GH •  Effects of estrogen on growth prior to bone maturaAon are not well understood poorly –  Androgens –  Estrogens 20 ...
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