L22_NPB_101 - Lecture 22 •  SmartSite: – ...

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Unformatted text preview: Lecture 22 •  SmartSite: –  Lecture 22 Notes •  Review –  Pineal –  Circadian Rhythms •  Announcements: –  Grades & Key Posted on SmartSite •  Class Mean = 18.8 •  Std Dev = 4.3 •  Endocrinology –  Thyroid –  Adrenal •  Reading (Recommended): –  Relevant porIons Chapter 19 1 REV: Pineal & CTS •  Pineal –  Produces Melatonin •  AnIoxidant •  Promotes immune and reproducIve funcIon •  Helps regulate Iming of sleep and other funcIons under direcIon of Circadian System •  Circadian Timing System (CTS) –  Physiological system responsible for regulaIng daily physiological and behavioral funcIons •  Contains a pacemaker measuring 24 ­hour day (SCN of the hypothalamus) •  Synchronizes internal rhythms and external relaIonship with the 24 ­hour day •  CTS alters Ime of day responses to sImuli 2 Peripheral Endocrine Glands •  Include –  Thyroid glands –  Adrenal glands –  Endocrine pancreas –  Parathyroid glands 3 Thyroid Gland 4 Thyroid Gland •  Consists of two lobes of endocrine Issue joined in middle by narrow porIon of gland •  Follicular cells –  Arranged into hollow spheres –  Forms funcIonal unit called a follicle –  Lumen filled with colloid –  Produce two iodine ­containing hormones derived from amino acid tyrosine •  Tetraiodothyronine (T4 or thyroxine) •  Tri ­iodothyronine (T3; most potent) •  C cells –  Secrete pepIde hormone calcitonin Fig. 19 ­1a, pg. 692 •  Serves as extracellular storage site for thyroid hormone 5 Thyroid Gland Anatomy Fig. 19 ­1b, pg. 692 6 Thyroid Hormone •  Synthesis, storage, and secreIon of thyroid hormone –  Basic ingredients •  Tyrosine •  Iodine –  Synthesized in sufficient amounts by body –  Obtained from dietary intake –  Synthesis •  All steps occur on thyroglobulin molecules within colloid •  Tyrosine ­containing thyroglobulin is exported from follicular cells into colloid by exocytosis •  Thyroid captures iodine from blood and transfers it into colloid by iodine pump •  Within colloid, iodine acaches to tyrosine •  Coupling process occurs between iodinated tyrosine molecules to form thyroid hormones 7 Thyroid Hormone –  Storage •  Thyroid hormones remain in colloid unIl they are split off and secreted •  Usually enough thyroid hormone stored to supply body’s needs for several months –  SecreIon •  Follicular cells phagocyIze thyroglobulin ­laden colloid •  Process frees T3 and T4 to diffuse across plasma membrane and into blood 8 Thyroid Hormone: Synthesis, Storage & SecreIon Fig. 19 ­2, pg. 693 9 Thyroid Gland •  Effects of thyroid hormone –  Main determinant of basal metabolic rate –  Influences synthesis and degradaIon of carbohydrate, fat, and protein –  Increases target ­cell responsiveness to catecholamines –  Increases heart rate and force of contracIon –  EssenIal for normal growth –  Plays crucial role in normal development of nervous system 10 Thyroid Hormone is regulated •  SecreIon –  Regulated by negaIve ­ feedback system between hypothalamic TRH, anterior pituitary TSH, and thyroid gland T3 and T4 –  Feedback loop maintains thyroid hormones relaIvely constant Fig. 19 ­3, pg. 695 11 Types of Thyroid DysfuncIon Table 19 ­1, pg. 696 12 Hyperthyroidism: Graves’ Disease •  AbnormaliIes –  Hyperthyroidism •  Most common cause is Graves’ disease –  Autoimmune disease –  Body erroneously produces thyroid ­sImulaIng immunoglobulins (TSI) –  Characterized by exopthalmos, goiter –  Weight loss, heat intolerance, insomnia, rapid heart rate •  Treatment –  Surgical removal of a porIon of the over ­secreIng thyroid –  AdministraIon of radioacIve iodine –  Use of anI ­thyroid drugs Fig. 19 ­4, pg. 696; Fig. 19 ­5, pg. 697 13 Hypothyroidism •  AbnormaliIes •  Causes –  Hypothyroidism –  Primary failure of thyroid gland –  Secondary to a deficiency of TRH, TSH, or both –  Inadequate dietary supply of iodine –  FaIgue, weight gain, weak pulse, cold intolerance, mental sluggishness and depression –  Goiter if due to thyroid hormone synthesis problem –  Reversible with TH replacement therapy or iodine in diet –  –  –  –  Human brain maturaIon depends on TH Short stature, poor motor skills, moderate to severe mental retardaIon Goiter if due to thyroid hormone synthesis problem Effects on nervous system irreversible if not corrected shortly amer birth •  Hypothyroidism as an adult •  Hypothyroidism during perinatal period: “CreInism” •  Myxedema •  Treatment –  Term omen used for myxedema in adults –  Replacement therapy –  Dietary iodine 14 Fig. 19 ­6, pg. 697 Adrenal Gland 15 Adrenal Glands •  Embedded above each kidney in a capsule of fat •  Composed of two endocrine organs –  Adrenal cortex •  Outer porIon •  Secretes steroid hormones –  Adrenal medulla •  Inner porIon •  Secretes catecholamines Fig. 19 ­7a, pg. 698 16 Adrenal Glands •  Adrenal cortex –  Consists of three layers or zones •  Zona glomerulosa – outermost layer •  Zona fasciculata – middle and largest porIon •  Zona reIcularis – innermost zone •  MineralocorIcoids •  GlucocorIcoids –  Mainly aldosterone –  Influence mineral balance, specifically Na+ and K+ balance –  Primarily corIsol –  Major role in glucose metabolism as well as in protein and lipid metabolism –  IdenIcal or similar to those produced by gonads –  Most abundant and physiologically important is dehydroepiandosterone (male “sex” hormone) 17 –  Categories of adrenal steroids •  Sex hormones The Adrenal Glands Low blood pressure Angiotensin II Aldosterone CorIsol (major) Sex steroid hormones (minor) CRH ACTH SympatheIc pre ­ganglionic neuron Ach “Catecholamines” Epinephrine (~80%) Norepinephrine (~20%) Fig. 19 ­7b, pg. 698 18 GlucocorIcoids (CorIsol) from the Adrenal Cortex starvaIon, emoIon Exercise, illness, pain, 6 am peak When given at high levels, immunosuppressive and anI ­inflammatory Processed from pro ­opiomelanocorIn: also produces endorphins Metabolic effects: Blood glucose levels Blood facy acid levels Blood amino acid levels Fig. 19 ­9, pg. 701 Permissive for sympatheIc acIvity 19 ...
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This note was uploaded on 11/15/2010 for the course BIO NPB 101 taught by Professor Dr.weidner during the Fall '10 term at UC Davis.

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