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Transcript
Physiology Unit3 ENDOCRINESYSTEM InPhysiologyToday HormoneClassification • AmineHormones – Tyrosine – Tryptophan • Peptide/ProteinHormones – Watersoluble • SteroidHormones – Lipidsoluble AmineHormones • DerivativesofTyrosine – Catecholamines • Epinephrine – Thyroidhormones • T3,T4 • Derivativesof Tryptophan – Serotonin(5-HT) – Melatonin • pinealgland PeptideandProteinHormones • PeptideHormones – <200aminoacids – ADH,ACTH,insulin,PTH, Calcitonin,ANF,GItract hormonesandothers • ProteinHormones – TSH,LH,FSH, erythropoietin,renin SteroidHormones • Derivedfrom cholesterol • Producedby – Adrenalcortex – Gonads • Testosterone • Estrogens • Progesterone SteroidHormones HormonesoftheAdrenalCortex • Aldosterone – Regulatesbloodpressure • Cortisol – Releasedinresponsetostress – Increasebloodsugar – Aidinmetabolism • Dehydroepiandrosterone (DHEA) – Androgen – Prohormone(precursor)forsex steroids HormoneTransportintheBlood MechanismofHormoneAction HormoneReceptors • Signal-transductionmechanism • Receptormodulation – Up-regulation – Down-regulation • LocationofReceptor – Lipidsoluble – Watersoluble MechanismofHormoneAction HormoneInteractions • Synergisticeffects - Epi/NEonheart • Permissive/Potentiation • HormoneAmustbe presentforafull strengthofhormoneB’s effect • Antagonisticeffects – Insulin/Glucagon – Calcitonin/PTH TheHypothalamusandPituitaryGland PVN and SON send axons to both the poserior pituitary and the portal vessel to the anterior pituitary Hyothalamus-Pituitary Axis PosteriorPituitaryHormones • PosteriorPituitaryisaneuralextensionofthehypothalamus • Neuronswhichprojectfromthehypothalamus • Hormonessynthesizedinthehypothalamus • Hormonespackagedintovesiclesmovedowntheaxonsinto theposteriorpituitary • Stimulioftheneuronsgenerateactionpotentialswhich triggerthereleaseofthehormones • Hormonesreleased – Oxytocin – Actsonsmoothmuscleoftheuterusandmammaryglands – Antidiuretichormone(ADH) – Decreaseswaterloss – Stimulatesthirst HypothalamusReleasingHormones Somatocrinin = GHRH HypothalamusandtheAnterior PituitaryHormones • Hypothalamusneuronssecretehormonesthat controlthesecretionofalltheanteriorpituitary hormones – Hypothalamusreleasingorinhibitinghormones • Eachofthereleasinghormonesisthefirstina three-hormonesequence 1. Hypothalamusreleasinghormone 2. Anteriorpituitarystimulatinghormone 3. Endocrineglandhormone • Allowsforfeedback,amplificationofresponse • AllarepeptidehormonesexceptDA AnteriorPituitaryHormonesandthe Hypothalamus AHypophysiotropic hormoneisreleasedfrom thehypothalamusandbindstoreceptorsin theAnteriorPituitary AnteriorPituitaryHormones Atropichormonehasanotherendocrineglandasitstargetorgan Hypothalamic-AnteriorPituitary System Short-Loopand Long-Loop Negative Feedback ThyroidHormones • Follicularcells – secreteTH • Producestwoiodine containingmolecules – Thyroxine(T4) – Triiodothyronine(T3) – T4 generallyconverted intoT3 intargetcells – Thyroglobulin • Thyroidbindinghormonein thyroidfollicles SynthesisofThyroidHormones ControlofThyroidFunction • BasiccontrolofThyroid Hormoneproductionis long-loopnegative feedback • TheprimaryroleofT4 in thebloodistofeed backtotheanterior pituitaryANDthe hypothalamus ActionsofThyroidHormones • THreceptorspresentinthenucleiofmostcellsof thebody • MetabolicActions – Maintainsrelativelyhighmetabolicrate – StimulatestheactivityofNa+/K+/ATPasepumps – Inducesgenetranscriptionandproteinsynthesis • PermissiveActions – Potentiatestheactionsofcatecholamines • GrowthandDevelopment – PotentiatesGH – Developmentandfunctionofthenervoussystem – Normalcognitioninadults EndocrineControlofGrowth BoneGrowth • • • • • • • GrowthHormone Insulin-LikeGrowthFactorsIandII Thyroidhormones Insulin Testosterone Estrogens Peptidegrowthfactors Ghrelin regulates energy homeostasis – Paracrine/autocrineagentstostimulate differentiation,celldivision EndocrineControlofGrowth GrowthHormone • Growthhormone(GH) – Mostimportanthormoneforpost-natalgrowth – Stimulus:exercise,stress,fasting,lowplasma glucose,sleep – Stimulatescelldivisioninmanytissues – Promotesbonelengthening – Stimulatesproteinsynthesisinmuscle – StimulateslivercellstosecreteIGF-I EndocrineControlofGrowth Insulin-LikeGrowthFactors • Insulin-LikeGrowthFactorI(IGF-I) – PotentiatesGHeffectsonbonegrowth • Stimulateschondrocytes – Requiredforfetaltotalbodygrowth,maturation offetalnervoussystem • Insulin-LikeGrowthFactorII(IGF-II) – Importantmitogenduringprenatalperiod EndocrineControlofGrowth ThyroidHormonesandInsulin • Thyroidhormones – Potentiatesgrowthhormone • Insulin – Uptakeofglucoseandaminoacidsbycells – Stimulatesstorageoffat – Inhibitsproteindegradation – Promotescelldivisionanddifferentiationinfetal development EndocrineControlofGrowth SexHormones • Sexhormonesecretionbeginstoincreasebetween theagesof8and10andplateausoverthenext5-10 years • Pubertalgrowthspurt – Growthoflongbones,vertebrae • StimulatesthesecretionofGHandIGF-I • Testosteroneexertsadirectanaboliceffecton proteinsynthesis – Increasesmusclemass EndocrineControlofCa2+Homeostasis • Ca2+homeostasisisvitalforsurvival – Lowplasma[Ca2+]Hypocalcemia • Increaseexcitabilityofnerve,musclemembranes – Highplasma[Ca2+]Hypercalcemia • Causescardiacarrhythmias • Causesdepressedneuromuscularexcitability • Ca2+homeostasisinvolvesbone,kidneys, parathyroidgland,skin,thyroidgland,GItract 2+ EndocrineControlofCa Homeostasis Bone • 99%oftotalbodyCa2+is containedinbone • Osteoclast/osteoblast activity • Ca2+fluxinto/outofboneis paramountincontrolling plasma[Ca2+] • Hydroxyapatiteiswhere mineralsaredeposited – Ca2+,PO43- 2+ EndocrineControlofCa Homeostasis Kidneys • ControlofCa2+excretionisexertedmainlyin thekidneys • Reabsorptiondecreaseswhenplasma[Ca2+] increases,andvisversa • HormonalcontrolsofCa2+alsoregulatePO43balance 2+ EndocrineControlofCa Homeostasis ParathyroidGland • Normal,day-to-dayregulationofplasma[Ca2+] • ParathyroidHormone(PTH) • Resultsinanincreaseinplasma[Ca2+] – Decreasedplasma[Ca2+]stimulatesPTHsecretion • Stimulatesosteoclastactivity • Stimulates1,25-dihydroxyvitaminD • IncreasesCa2+reabsorptioninthekidneys 2+ EndocrineControlofCa Homeostasis Skin • Normal,day-to-dayregulationofplasma[Ca2+] • 1,25-dihydroxyvitaminD(calcitrol)istheactiveform ofVitaminD • Resultsinanincreaseinplasma[Ca2+] • Synthesizedintheskin • Dietarysupplement • IncreasesabsorptionofCa2+andPO43- bythe intestines 2+ EndocrineControlofCa Homeostasis ThyroidGland • Not involvedinnormal,day-to-dayregulation ofplasma[Ca2+] • Calcitonin – Peptidehormonesecretedbyparafollicularcells ofthethyroid • Resultsinadecreasesplasma[Ca2+] – Stimulatedbyanincreaseinplasma[Ca2+] • Inhibitsosteoclasts EndocrineControlofGlucoseHomeostasis Pancreas • Insulin – Producedbypancreatic isletβcells – Stimulatedbyincreased bloodglucose – Stimulatescellular uptake(liver,skeletal muscle,adipocytes)and utilizationofglucose • Glucagon – Producedbypancreatic isletαcells – Stimulatedbydecreased bloodglucose – Stimulates liverto releaseglucose – Stimulates skeletal muscle,adipocytesto decreaseglucoseuptake andutilization