Download Endocrine Physiology

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