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TheEndocrineSystem

AtifH.Khirelsied,Ph.D.

DepartmentofBiochemistry,

FacultyofMedicineandHealthSciences

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TheEndocrineSystem

Sameasnervoussystem:communicationandcontrol

Sloweractingthannervoussystem

Effectsare

longer

lasting

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TheEndocrineSystem

Hormoneshel re ulate:

extracellularfluid

biologicalclock

glandularsecretion

growthanddevelopment

repro uction

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TheMajor

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TheEndocrineGlands

Exocrine lands

secreteproductsintoductswhichemptyintobodycavities

orbody

surface

sweat,oil,mucousanddigestiveglands

Endocrineglands

pituitary,thyroid,parathyroid,adrenal,pineal

o erorganssecre e ormonesasasecon ary unc on

hypothalamus,thymus,pancreas,ovaries,testes,kidneys,

185

, , ,

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TheEndocrineGland

Target

cells

Cellsofendocrineglandsreleasehormones,intotheextracellularfluid.

u

throughoutthe

body.

From:Textbookofmedicalphysiology/ArthurC.Guyton,JohnE.Hall.11thed.

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Thecirculatinghormones

actondistanttar ets

travelin

blood

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Thelocalhormones

Autocrine actson

same

cell

that

secreted

them

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Hormonesaffecttargetcellswithspecificreceptors

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Hormonesarechemicallydiversesubstances

Hormonesarechemical messengersconsistingofavarietyofsubstances

Proteins

Hormones

ers

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HydrophobicHormones(typeI hormones)

Steroids

derivedfromcholesterol

Thyroidhormones

Nitricoxideis as

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HydrophilicHormones(typeIIhormones)

,

modifiedaminoacidsorpeptides

, , ,

epinephrine

Eicosanoids

derivedfrom

arachidonic acid

(fattyacid)

prostaglandinsorleukotrienes

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Hormonestransportinblood

Protein hormones circulate in free form in blood.

synthesizedbyliver.

Preventlossofhormone.

a n a n e me.

Createreserveofhormone.

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MechanismsofHormonesAction

Hormonebindstocellsurfaceorreceptorinsidetargetcell

Cellmaythen;

changepermeabilityofmembrane

livercellsinsulinstimulatesglycogensynthesis

a pose nsu ns mu a es r g ycer esyn es s

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MechanismsofActionofTypeI Hormones

Hormonediffusesthrou h lasmamembraneintocell.

.

Alter

mRNA

and

proteins

synthesis.

Changeinproteinsconcentrationalterscellsactivity

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MechanismsofActionofTypeI Hormones

From:Textbookofmedicalphysiology/ArthurC.Guyton,JohnE.Hall.11thed.

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MechanismsofActionofTypeI Hormones

From:Textbookofmedicalphysiology/

ArthurC.Guyton,JohnE.Hall.11thed.

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From:Textbookofmedicalphysiology/ArthurC.Guyton,JohnE.Hall.11thed.

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MechanismsofActionofTypeI Hormones

From:HarpersReviewofBiochemistry28th ed.

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MechanismsofActionofTypeII Hormones

Cannotdiffusethrou h lasmamembrane

Receptorprotein

activates

other

proteins

(G

protein)

Formationofintracellularsecondmessenger

Resultsinamplificationofhormoneeffects

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AmplificationofHormoneEffect

Singlemoleculeofhormonebindstoreceptoractivates100

Gproteins

EachGproteinactivatesanadenylate cyclase molecule

whichthenproduces1000cAMP.

EachcAMP activatesa roteinkinase whichma actu on

1000sofsubstratemolecules.

Onemoleculeofepinephrinemayresultinbreakdownof

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MechanismsofActionofTypeII Hormones

From:Textbookofmedicalphysiology/ArthurC.Guyton,JohnE.Hall.11thed.

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MechanismsofActionofTypeII Hormones

From:HarpersReviewofBiochemistry28th ed.

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From:Textbookofmedicalphysiology/ArthurC.Guyton,JohnE.Hall.11thed.

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MechanismsofActionofTypeII Hormones

From:HarpersReviewofBiochemistry28th ed.

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MechanismsofActionofTypeII Hormones

From:RichardE.Klabunde,Ph.D. cardiovascularPharmacologyConcepts

h f f ld f l ( )

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MechanismsofActionofSildenafil (viagra)

M h i f A i f T II H

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MechanismsofActionofTypeII Hormones

From:Textbookofmedicalphysiology/ArthurC.Guyton,JohnE.Hall.11thed.