Endocrine System

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  • 1. The Endocrine System

2. What is Hormone? A regulatory substance and chemical messengerreleased by one cell to regulate another cell.Delivered throughendocrine, neuroendocrine, neurocrine, paracrine, autocrine system to act on the target cells. Some hormones affect on many tissues: Eg: Growth hormone, Thyroid hormone &Insulin. Some affect on specific tissues (Target tissues): Eg: Thyroid stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) 3. Condt.. Endocrine: Endocrine hormones travel viablood stream to target cells. Neurocrine: Neurocrine hormones releasedvia synapses and travel via blood stream. Paracrine: Paracrine hormones acts onadjacent cells. Autocrine: Autocrine hormones acts on thecell that secreted them. 4. Distance of Travelled Hormone 5. Principles of Hormone Need to maintain Homeostatic level. Regulation of growth and development. Control and maintenance of reproductionincluding fertilization and fetal growth andnourishment and development of thenewborn. Regulation of the metabolism. 6. Endocrine System 7. General principle of Endocrinology The glands of internal secretion.End = IntoCrin = Secrete The bodys great 2nd controlling system which iscontrolled metabolic activity of cells by hormones. A ductless gland composed of epithelial cells, thatsecreted hormones directly into extracellular fluid. From the ECF the hormones diffuse into thebloodstream. 8. Cond.. Central Endocrine glands 1. Pineal gland 2. Hypothalamus 3. Pituitary glandPeripheral Endocrine glands 4. Thyroid 5. Parathyroid 6. Thymus 7. Adrenal glands 8. Pancreas 9. Gonads (Ovaries & Testes)Other tissues and organs that produced hormones adipose cells, cells of the small intestine, stomach, kidneys, and heart. 9. Chemistry of hormones can be.. Proteins and Polypeptides: Hormones fromanterior and posteriorpituitary, Pancreas, parathyroid gland. Usuallyreleased into blood stream via exocytosis. Steroid hormones: Hormones from adrenalcortex, ovaries and testes. These are usuallysynthesized from cholesterol. Amine hormones: Thyroid and adrenalmedullary hormones. They are derived fromtyrosine. 10. Condt.. Hydrophilic and Lipophobic Peptide work via a second messenger Adenylate cyclase ATP 2,3 cAMP Catecholamines via 2nd messengers. Hydrophobic Thyroxine Steroid 11. A structural classification of hormones 12. Synthesis of hormones1. (Protein) In the nucleus, the gene for hormone transcribed into mRNA.2. The mRNA transferred to cytoplasm and translated on ribosome of ER to the first protein(peptide chain) product a preprohormone.3. The chain is directed into the ER lumen by a signal sequence of amino acids.4. The enzyme of ER cleaved the signal sequence, to create an inactive prohormone.5. The prohormone passes from the RE through the golgi apparatus.6. And prohormone bud off the Golgi.7. Secretory vesicles containing enzyme which is cleaved the prohormone into one or more active peptides.8. The secretory vesicle releases its contents by exocytosis into extra cellular space.9. The hormone moves into the circulation for transport to its target. 13. Steroid HormonesAre not packaged, but synthesized andimmediately released.All are derived from cholesterol. These arelocated in mitochondria and smooth ER.Steroids are lipid soluble and thus arepermeable to membranes so are not stored incell.Steroids hormones are not water soluble sohave to be carried in the blood complexed tospecific globulins.Corticosteroid binding globulin carries cortisol.Sex steroid binding globulin carriestestosterone and estradiol. 14. Types of steroids Glucocorticoids: cortisol is the majorrepresentative in most mammals. Mineralocorticoids: aldesterone being mostprominent. Androgens: such as testosterone. Estrogen: including estradiol, and estrone. Progestogens: ( also known a progestins)such as progesterone. 15. Amine hormonesTwo types of hormones derived from the amino acid tyrosine. Thyroid hormones and CatecholaminesThyroid hormones are basically a double tyrosine with the critical incorporation of3 or 4 iodine atoms.Thyroid hormone is produced by the thyroid gland and is lipid soluble.Catecholamine hormonesCatecholamines both are both neurohormones and neurotransmitters.These include epinephrine and norepinephrine both are produced by adrenalmedulla and both are water soluble.Secreted like peptide hormones. 16. Condt.. Two other amino acids are used forsynthesis of hormones: Tryptophan is precursor to serotonin and the pineal hormone melatonin. Glutamic acid is converted to histamine. 17. Hormones and theirreceptors 18. Hormone Transport In BloodMost water soluble hormonescirculates in plasma infree, unattached form.Most lipid soluble hormonesbind to transport proteins to becarried in blood.Protein and peptidehormones, such as insulin, willbe destroyed by digestiveenzymes and must be given byinjection. 19. Mechanism of Hormone action Hormones bind and activate their specific receptors in two differentways. Steroid hormones and thyroid affect cell function by binding andactivating an intracellular receptor( usually in nucleus). Water soluble hormones alter cell function by activating plasmamembrane receptors. After a water soluble hormones is released from an endocrine gland, itcirculates in the blood, reaches a target cell, and brings a specificmessage to that cell. The plasma membrane is 1st messenger. A 2nd messenger needed to relay the message inside the cell wherehormone-stimulated take place. 2n messenger is cyclic AMP (cAMP) G-proteins are a common feature of the most second messengersystem. 20. Condt.. Cyclic AMP does notdirectly produce aparticularphysiologicalresponse, butinstead activates oneor more enzymesknown as proteinkinases. The responsivenessof target cell to ahormone depends onthe hormonesconcentration andthe number ofreceptors. 21. Steroid (Water insoluble) Hormone Transport Most water- soluble hormones circulate in plasma in a free, unattachedform. Most lipid- soluble hormones bind to transport protein to be carried inblood. The transport proteins improve the transportability of lipid solublehormones by making them temporarily water soluble, retard the passageof the hormone through the kidney filter and slowing the rate of hormoneloss in urine. And provide reserve of hormone already present in hormone. Protein and peptide hormones, such as insulin, will be destroyed bydigestive enzymes and must be given by injection. Lipid soluble hormones bind and activate receptors within cell. The activated receptors then alter gene expression to form of the newprotein. The new proteins alter the cells activity and affect in the physiologicalresponses of those hormones. 22. Protein (water soluble) HormoneTransport hormones binds on the plasma receptor to alter the cell function. Water soluble The cell membrane receptor is 1st messenger. 2nd messenger is released when hormone stimulates response takes place insideof cell. Typical action of water soluble hormones are using cyclic AMP as the 2ndmessenger. Firstly the hormone bind to the membrane receptor. The activated receptor activate s the membrane G-protein which turns onadenylate cyclase. Adenylate cyclase converts ATP into cyclic AMP which activate protein kinase. Priotein kinases phosphorilated enzyme which catalyze reaction produce thephysiological response. 23. Condt.. The cholera toxin modifies G-proteins inintestine epithelial cells so they becomelocked in an activated 24. Regulation Of Hormone Hormone secretion iscontrolled by homeostaticfeedback. Negative feed backmechanisms that reversethe direction of a changein physiological system. Positive feedback (Uncommon) Mechanisms that amplifyphysiological changes. 25. Prostaglandins Prostaglandins (PGs) are powerful substances found in awide variety of body tissues. It is a local regulator(Paracrine Signals) of hormone. PGs are often produced in a tissue and diffuse only ashort distance to act on cells in that tissue. Several classes of PGs includeprostaglandinA, prostaglandin E and prostaglandin F Pgs influence many body functions, includingrespiration, blood pressure, gastrointestinalsecretions, and reproduction. 26. Control of EndocrineSystem 27. Central Endocrine System Hypothalamus : receives information from the nervoussystem and initiates responses through the endocrinesystem. Pituitary: Attached to the hypothalamus. Composed ofposterior pituitary and anterior pituitary. Pineal Gland: Pineal gland is located just posterior to the3rd ventricle in the brain. Secrete Melatonin regulates circadian rhythms. May induce sleep May initiate puberty May inhibit ovulation/ spermatogenesis May slow aging May enhance immunity 28. Pituitary Gland Anterior pituitary gland; name ofhormones: TSH Thyroid stimulating hormones ACTH Adrenocorticotropic hormone FSH Follicle stimulating hormone LH Luteinizing hormone GH Growth hormone Prolactin 29. Functions of Hormones TSH stimulate growth of thyroid gland, alsostimulate its hormone secretion. ACTH: stimulates growth of the adrenal cortex andstimulate it to secrete glucocorticoids (mainlycortisol) FSH initiates growth of ovarian follicles each monthin ovary and stimulates one or more follicles todevelop to the stage of maturity and ovulation. FSH also helps to secretion of estrogen bydeveloping follicles and stimulate sperm productionin male. 30. Condt.. LH acts with FSH to stimulate estrogen secretion andfollicle growth to maturity. Stimulate the progesteronesecretion by corpus luteum. And stimulate thetestosterone in the male. GH Stimulates growth by accelerating anabolism; alsoaccelerates fat catabolism and slows glucose catabolism;by slowing glucose catabolism, tends to increase bloodglucose to higher than normal level (hyperglycemia) Hyper secretion during childhood results in gigantism and duringadult hood results in acromegaly. Hypo secretion during child hood results in pituitary dwarfism.o Prolactin stimulates breast devel