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Endocrine System

Endocrine System. Biology 2122. Introduction. (1) What are hormones? (2) What are the functions of hormones? (3) What are the types of hormones? Amino Acids Steroids Eicosanoids. How do Hormones Work?. (1) Action on Target Cells Membrane permeability Synthesis of proteins or enzymes

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Endocrine System

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  1. Endocrine System Biology 2122

  2. Introduction (1) What are hormones? (2) What are the functions of hormones? (3) What are the types of hormones? • Amino Acids • Steroids • Eicosanoids

  3. How do Hormones Work? (1) Action on Target Cells • Membrane permeability • Synthesis of proteins or enzymes • Or inhibits • Induces secretory activity • Stimulates mitosis (2) Target-Specific • Target cell receptor sites • “Turns on cell” • “Dynamic”

  4. How do Hormones Work? (3) Half-Life (4) Interaction – Target Cells • Permissive • Synergistic • Antagonistic (5) Control of Release • Negative feedback • Endocrine Gland Stimuli • Humoral stimuli • Neural stimuli • Hormonal stimuli

  5. Plasma Membrane Receptors (1) Second Messenger System • All amino acid hormones (except thyroid)

  6. Plasma Membrane Receptors (2) Intracellular – Direct Gene Activation • Lipid soluble; steroid • Binds to intracellular receptors • Binds to DNA • Activates a gene

  7. Anterior Pituitary Hormones-HGH (1). Somatotroph cells produce GH (2). Secretion • GHRH – stimulates release (GHIH) inhibits • Produced in the hypothalamus (3). Effects • Anabolic – protein synthesis • Targets bones and muscles • Stimulates epiphyseal plates during development (4). Disorders • Gigantism and Acromegaly

  8. Thyroid-Stimulating Hormone • (1). Also referred to as thyrotropin. • Produced by thyrotroph cells • (2). Secretion • TRH or thyrotropin releasing hormone stimulates the release of TSH • Negative feedback – rising levels of thyroid hormones • ANIMATION • (3). Effects • Moderates normal thyroid gland activity.

  9. Adrenocorticotropic Hormones • (1). ACTH – adrenocorticotropic hormone secreted • corticotroph cells • (2). Stimulation-Secretion • CRH – corticotropin-releasing hormone – hypothalamus • Levels peak in the morning • Negative feedback • (3). Effects • Stimulates the Adrenal gland (cortex) to release Glucocorticoids • Cortisol (stress hormone)

  10. Gonadotropins • (1). FSH and LH – gonadotrophic cells • (2). Stimulus-Secretion • Puberty • GnRH – prompts the anterior pituitary to release hormones • ANIMATION • (3). Effects • (a). LH • FSH -maturation of follicle • Ovulation • Stimulates interstitial cells - testosterone in males • (b). FSH – stimulates gamete production; follicle development.

  11. Prolactin (1). PRL or prolactin is a protein hormone. • Produced by the lactrotroph cells (2). Stimulus – Secretion • PRH and PRH • PRH plays dominant role – dopamine prevents secretion (3). Effects • Stimulate milk production in the breasts

  12. Acromegaly

  13. Posterior Pituitary Gland Hormones (1). Production- hypothalamic neurons (2). ADH or Antidiuretic Hormone • Reabsorption of water– collecting tubules • Release stimulated by – increasing osmolarity • Diabetes insipidus (3). Oxytocin • Stimulated release by positive feedback – contractions during birth • Milk ejection • Synthetic – induce contractions

  14. Thyroid Gland (1). Produces TH or thyroid hormones • T4 or thyroxin; T3 or triiodonthyronine (2). Stimulus – Secretion • Hypothalamus (TRH) - Pituitary (TSH) -- TH • Stress - cold, pregnancy – cause hypothalamus to produce TRH. • Rising TH levels – negative feedback to hypothalamus-pituitary axis. (3). Effects • Increases BMR • body heat production (stimulates enzymes to increase glucose oxidation)

  15. Synthesis of TH

  16. Thyroid Imbalances • (1). Myxedema – hypothyroid • (2). Goiter • (3). Cretinism • Infant hypothyroidism • (4). Grave’s Disease • Hyperthyroid

  17. Calcitonin (1). Polypeptide hormone • Parafollicular cells of the thyroid • Lowers calcium blood levels • Reabsorption back into the bones (2). Stimulus for release • 20% above normal levels for calcium blood levels • Lower than normal – inhibitory effect (3). More important in childhood • Due to developing bones and keeps calcium levels in check

  18. Parathyroid Hormones (1). Cells in the parathyroid gland • Oxyphil and chief cells (secretes ) PTH (2). Stimulus and Secretion • Hypocalcemia ----- PTH

  19. Adrenal Hormones (1). Adrenal gland has two distinct regions • (a). Cortex - outer region • (b). Medulla - inner region (2). Hormones produced • corticosteroids • 12 total (3). Steroid Hormones • Not stored in cells – rate of release depends on productivity (4). Cortical regions • (a). Zonaglomerulosa– mineralocorticoids • (b). Zonafasciculata– glucocorticoids • (c). Zonareticualaris– adrenal sex hormones called gonadocorticoids.

  20. Mineralocorticoids (1). Produced in the zona glomerulosa of the cortex • Mostly aldosterone • Balances ions and water (2). Stimulus and Secretion • Renin-angiotensin mechanism • Elevated K+ levels (3). Disorders • Aldosteronism • Addison’s disease

  21. Glucocorticoids (1). Produced in the zonafasciculata • Metabolic hormones (2). Cortisol is the main hormone • Gluconeogenesis; lipolysis; protein metabolism (3). Stimulation and secretion • ACTH from the anterior pituitary (low levels of hormones) (4). Disorders • Cushing’s syndrome • Addison’s disease

  22. Gonadocorticoids (1). Androgens produced in the zonareticularis • Converted to testosterone and estrogen (2). Stimulus and secretion • ACTH released from anterior pituitary (3). Effects • Males • Female libido; pubic and axillary hair in females; estrogen after menopause

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