endocrine system - mt. sac faculty directoryfaculty.mtsac.edu/mpresch/36_lecture_files_unit_3/14...
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HormoneClassification
• AmineHormones– Tyrosine– Tryptophan
• Peptide/ProteinHormones–Watersoluble
• SteroidHormones– Lipidsoluble
AmineHormones
• DerivativesofTyrosine– Catecholamines
• Epinephrine
– Thyroidhormones• T3,T4
• DerivativesofTryptophan– Serotonin(5-HT)– Melatonin
• pinealgland
PeptideandProteinHormones
• PeptideHormones– <200aminoacids– ADH,ACTH,insulin,PTH,Calcitonin,ANF,GItracthormonesandothers
• ProteinHormones– TSH,LH,FSH,erythropoietin,renin
SteroidHormones
• Derivedfromcholesterol
• Producedby– Adrenalcortex– Gonads• Testosterone• Estrogens• Progesterone
SteroidHormonesHormonesoftheAdrenalCortex
• Aldosterone– Regulatesbloodpressure
• Cortisol– Releasedinresponsetostress– Increasebloodsugar– Aidinmetabolism
• Dehydroepiandrosterone(DHEA)– Androgen– Prohormone(precursor)forsex
steroids
MechanismofHormoneActionHormoneReceptors
• Signal-transductionmechanism• Receptormodulation– Up-regulation– Down-regulation
• LocationofReceptor– Lipidsoluble–Watersoluble
MechanismofHormoneActionHormoneInteractions
• Synergisticeffects- Epi/NEonheart
• Permissive/Potentiation• HormoneAmustbepresentforafullstrengthofhormoneB’seffect
• Antagonisticeffects– Insulin/Glucagon– Calcitonin/PTH
TheHypothalamusandPituitaryGland
Hyothalamus-Pituitary Axis
PVN and SON send axons to both the poserior
pituitary and the portal vessel to the anterior
pituitary
PosteriorPituitaryHormones• PosteriorPituitaryisaneuralextensionofthehypothalamus• Neuronswhichprojectfromthehypothalamus
• Hormonessynthesizedinthehypothalamus• Hormonespackagedintovesiclesmovedowntheaxonsinto
theposteriorpituitary• Stimulioftheneuronsgenerateactionpotentialswhich
triggerthereleaseofthehormones• Hormonesreleased– Oxytocin
– Actsonsmoothmuscleoftheuterusandmammaryglands
– Antidiuretichormone(ADH)– Decreaseswaterloss– Stimulatesthirst
HypothalamusandtheAnteriorPituitaryHormones
• Hypothalamusneuronssecretehormonesthatcontrolthesecretionofalltheanteriorpituitaryhormones– Hypothalamusreleasingorinhibitinghormones
• Eachofthereleasinghormonesisthefirstinathree-hormonesequence1. Hypothalamusreleasinghormone2. Anteriorpituitarystimulatinghormone3. Endocrineglandhormone
• Allowsforfeedback,amplificationofresponse• AllarepeptidehormonesexceptDA
AnteriorPituitaryHormonesandtheHypothalamus
AHypophysiotropic hormoneisreleasedfromthehypothalamusandbindstoreceptorsintheAnteriorPituitary
ThyroidHormones• Follicularcells– secreteTH
• Producestwoiodinecontainingmolecules– Thyroxine(T4)– Triiodothyronine(T3)– T4 generallyconvertedintoT3 intargetcells
– Thyroglobulin• Thyroidbindinghormoneinthyroidfollicles
ControlofThyroidFunction
• BasiccontrolofThyroidHormoneproductionislong-loopnegativefeedback
• TheprimaryroleofT4 inthebloodistofeedbacktotheanteriorpituitaryANDthehypothalamus
ActionsofThyroidHormones• THreceptorspresentinthenucleiofmostcellsofthebody
• MetabolicActions– Maintainsrelativelyhighmetabolicrate– StimulatestheactivityofNa+/K+/ATPasepumps– Inducesgenetranscriptionandproteinsynthesis
• PermissiveActions– Potentiatestheactionsofcatecholamines
• GrowthandDevelopment– PotentiatesGH– Developmentandfunctionofthenervoussystem– Normalcognitioninadults
EndocrineControlofGrowthBoneGrowth
• GrowthHormone• Insulin-LikeGrowthFactorsIandII• Thyroidhormones• Insulin• Testosterone• Estrogens• Peptidegrowthfactors– Paracrine/autocrineagentstostimulatedifferentiation,celldivision
Ghrelinregulatesenergy
homeostasis
EndocrineControlofGrowthGrowthHormone
• Growthhormone(GH)–Mostimportanthormoneforpost-natalgrowth– Stimulus:exercise,stress,fasting,lowplasmaglucose,sleep
– Stimulatescelldivisioninmanytissues– Promotesbonelengthening– Stimulatesproteinsynthesisinmuscle– StimulateslivercellstosecreteIGF-I
EndocrineControlofGrowthInsulin-LikeGrowthFactors
• Insulin-LikeGrowthFactorI(IGF-I)– PotentiatesGHeffectsonbonegrowth• Stimulateschondrocytes
– Requiredforfetaltotalbodygrowth,maturationoffetalnervoussystem
• Insulin-LikeGrowthFactorII(IGF-II)– Importantmitogenduringprenatalperiod
EndocrineControlofGrowthThyroidHormonesandInsulin
• Thyroidhormones– Potentiatesgrowthhormone
• Insulin– Uptakeofglucoseandaminoacidsbycells– Stimulatesstorageoffat– Inhibitsproteindegradation– Promotescelldivisionanddifferentiationinfetaldevelopment
EndocrineControlofGrowthSexHormones
• Sexhormonesecretionbeginstoincreasebetweentheagesof8and10andplateausoverthenext5-10years
• Pubertalgrowthspurt– Growthoflongbones,vertebrae
• StimulatesthesecretionofGHandIGF-I• Testosteroneexertsadirectanaboliceffectonproteinsynthesis– Increasesmusclemass
EndocrineControlofCa2+Homeostasis
• Ca2+homeostasisisvitalforsurvival– Lowplasma[Ca2+]Hypocalcemia• Increaseexcitabilityofnerve,musclemembranes
– Highplasma[Ca2+]Hypercalcemia• Causescardiacarrhythmias• Causesdepressedneuromuscularexcitability
• Ca2+homeostasisinvolvesbone,kidneys,parathyroidgland,skin,thyroidgland,GItract
EndocrineControlofCa2+HomeostasisBone
• 99%oftotalbodyCa2+iscontainedinbone
• Osteoclast/osteoblastactivity
• Ca2+fluxinto/outofboneisparamountincontrollingplasma[Ca2+]
• Hydroxyapatiteiswheremineralsaredeposited– Ca2+,PO4
3-
EndocrineControlofCa2+HomeostasisKidneys
• ControlofCa2+excretionisexertedmainlyinthekidneys
• Reabsorptiondecreaseswhenplasma[Ca2+]increases,andvisversa
• HormonalcontrolsofCa2+alsoregulatePO43-
balance
EndocrineControlofCa2+HomeostasisParathyroidGland
• Normal,day-to-dayregulationofplasma[Ca2+]
• ParathyroidHormone(PTH)• Resultsinanincreaseinplasma[Ca2+]– Decreasedplasma[Ca2+]stimulatesPTHsecretion
• Stimulatesosteoclastactivity• Stimulates1,25-dihydroxyvitaminD• IncreasesCa2+reabsorptioninthekidneys
EndocrineControlofCa2+HomeostasisSkin
• Normal,day-to-dayregulationofplasma[Ca2+]
• 1,25-dihydroxyvitaminD(calcitrol)istheactiveformofVitaminD
• Resultsinanincreaseinplasma[Ca2+]• Synthesizedintheskin• Dietarysupplement• IncreasesabsorptionofCa2+andPO4
3- bytheintestines
EndocrineControlofCa2+HomeostasisThyroidGland
• Not involvedinnormal,day-to-dayregulationofplasma[Ca2+]
• Calcitonin– Peptidehormonesecretedbyparafollicularcellsofthethyroid
• Resultsinadecreasesplasma[Ca2+]– Stimulatedbyanincreaseinplasma[Ca2+]
• Inhibitsosteoclasts
EndocrineControlofGlucoseHomeostasisPancreas
• Insulin– Producedbypancreaticisletβcells
– Stimulatedbyincreasedbloodglucose
– Stimulatescellularuptake(liver,skeletalmuscle,adipocytes)andutilizationofglucose
• Glucagon– Producedbypancreaticisletαcells
– Stimulatedbydecreasedbloodglucose
– Stimulates livertoreleaseglucose
– Stimulates skeletalmuscle,adipocytestodecreaseglucoseuptakeandutilization