ENDOCRINE PHYSIOLOGY ENDOCRINE PHYSIOLOGY Dr.P.Sn.Raju Asst Prof , Physiology Andhra medical college Endocrine Physiology Endocrine Physiology
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ENDOCRINE PHYSIOLOGYENDOCRINE PHYSIOLOGY
Dr.P.Sn.Raju
Asst Prof , Physiology
Andhra medical college
Endocrine PhysiologyEndocrine Physiology
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ENDOCRINE PHYSIOLOGYENDOCRINE PHYSIOLOGY
INTROD !TION INTROD !TION 1. Endocrine Gland2. Hormones3. Hormone receptors4. Chemical structure & synthesis5. Hormone secretion, transport and clearance
6. Feed ac! control". #echanism o$ action
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%ody s '(o #a)or *e+ulatory ystems%ody s '(o #a)or *e+ulatory ystems
• The endocrine system is one of the body’s two majorregulatory systems. The other one is the nervoussystem.
•In general, nervous system coordinates rapid,precise responses and is especially important inmediating the body’s interaction with the externalenvironment.
• The endocrine, by contrast, primarily controlsactivities that require duration rather than speed. Itregulates, coordinates, and integrates cellular andorgan function at distance.
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-E* /0 & E- /C* -E 'E#-E* /0 & E- /C* -E 'E#
• -E* /0 'E#• *E• CHE# C78 G-78
7' '7*GE' CE88• *79• %* EF 0*7' /-• C8/ E 7-7'/# C78
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• E- /C* -E 'E#• *E8E• CHE# C78 G-78
- %8// .• 8/
• 8/-G 0*7' /-• 9EC F C
*ECE9'/*
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8/C7' /- /F E- /C* -E G87-8/C7' /- /F E- /C* -E G87-
ORGAN HORMONES
HEART ANP
GIT CCK-PZ,SECRETIN, VIP
KIDNEY ERYTHROPOIETIN, 1,25-DHCC
PINEAL GLAND MELATONIN
SKIN CALCIFEROL(V
it-D3)LIVER IGF-I, II
PLATELET PDGF
LYMPHOCYTES IL
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Endocrine GlandsEndocrine Glands
Organs and Tissues of the ndocrine !ystem.
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Organs and Tissues of the ndocrine !ystem.
Endocrine GlandsEndocrine Glands
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'he Functions o$ Endocrine ystem'he Functions o$ Endocrine ystem". #egulating organic metabolism , $ %O and
electrolyte balance, which are important collectivelyin maintaining a constant internal environment.
%. Inducing adaptive changes to help the body cope up with stressful situations.
&. 'romoting smooth, sequential growth anddevelopment.
(. )ontrolling reproduction.
*. #egulating red blood cell production.
+. long with the autonomic nervous system,controlling and integrating activities of both thecirculatory and digestive systems.
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Endocrine Gland ?Endocrine Gland ?
• -land is structure which produces something.• ndocrine -lands might be small but of great
importance.
• Terms ndon / within , 0rinein1 to separate.• )alled as 2uctless glands.• 3ses chemical signals for cell to cell
communication• )oordinates the function of cells• #esponse to an endocrine signal occurs within
minutes to hours
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Chemical *e+ulatin+ ystems; /<er<ie(Chemical *e+ulatin+ ystems; /<er<ie(
• 'heromones / 4ehavior altering agents,organism to organism communication.
• $ormones• $ormonein / gree5 term , 6to rouse7
6 to !timulate7• cell to cell communication molecules
• 8ade in gland9s: or cells• Transported by blood• 2istant or local target tissue receptors• ctivates physiological response
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'ypes o$ hormones'ypes o$ hormones
• F !"ti#!$%• ndocrine $ormones / Travel through the blood to act at
a site distant from the secreting cell or gland• 'aracrine $ormones / ct on cells near the secreting cell• utocrine $ormones / ct on the secreting cell• ;eurocrine $ormones / !ecreted by neural cells
• neurotransmitters• neurohormones
• C&' i"$%• 'rotein < 'olypeptide• mine 9amino acid derived:• !teroid
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Chemical #essen+erChemical #essen+er• The multiple activities of the cells, tissues, and
organs of the body are coordinated by the interplayof several types of chemical messenger systems.
• !everal types of chemical messenger systems
a. Neurotransmitters are released by axonterminals of neurons into the synaptic junctionsand act locally to control nerve cell functions.
xample acetylcholine.
b. Endocrine hormones are released by glands orspeciali=ed cells into the circulating blood andin>uence the function of cells at another locationin the body.
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Chemical #essen+erChemical #essen+er
c. Neuroendocrine hormones are secreted by neurons into thecirculating blood and in>uence the function of cells at anotherlocation in the body. xamples oxytocin, vasopressin.
d. Paracrines are secreted by cells into the extracellular >uid andaffect neighboring cells of a different type. xample somatostatinsecreted by delta cells in the pancreas.
e. Autocrines are secreted by cells into the extracellular >uid andaffect the function of the same cells that produced them by bindingto cell surface receptors. xamples somatomedin, some growth
factors. f. Cytokines are peptides secreted by cells into the extracellular >uid
and can function as autocrines, paracrines, or endocrine hormones.xample interleu5ins.
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ntercellular Communicationntercellular Communication
Cell Target Cell
Cell
Cell Target Cell
Target Cell Neuron
Hormone
Hormone
Hormone Hormone
Hormone
Hormone
Hormone
Endocrine
Paracrine
Autocrine
Blood
Neuroendocrine
Blood
Interstitial Fluid
Interstitial Fluid
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• !ignal )hemicals• 8ade in endocrine cells• Transported via blood• #eceptors on target cells
8on+ istance Communication; EndocrineHormones8on+ istance Communication; EndocrineHormones
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-euro hormones-euro hormones
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9aracrine and 7utocrine Hormones9aracrine and 7utocrine Hormones
• ?ocal communication• !ignal chemicals
diffuse to target• xample )yto5ines
• utocrine/receptoron same cell
• 'aracrine/neighboring cells
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• Peptide & Protein Hormones• Steroid Hormones
• Amine Hormones
Classes of Hormones
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Hormones = 7 tructural Classi$icationHormones = 7 tructural Classi$ication
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Classes o$ HormonesClasses o$ Hormones
4ased on their solubility in water or lipid
a. @ater1soluble hormones 9hydrophilic: 'olarsubstances 1 peptides and catecholamines.
b. ?ipid1soluble hormones 9lipophilic: ;on 'olar 1
steroid and thyroid hormones.
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Hormone *eceptorsHormone *eceptors
The locations for the different types of hormonereceptors are generally the following
$ I! #* #! t&' + * $"' # t&' "'%% ' *$!' Themembrane receptors are speciAc mostly for the protein, peptide, and catecholamine hormones .
I! t&' "'%% ".t#/%$+ The primary receptors forthe different steroid hormones are found mainly in
the cytoplasm." I! t&' "'%% ! "%' + The receptors for the thyroid
hormones are found in the nucleus and are believed to be located in direct association with one or more ofthe chromosomes.
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*eceptor locations*eceptor locations
• )ell membrane• ?ipophobic ligand canBt
enter cell• Outer surface receptor• Cast response
• )ytosolic or ;uclear• ?ipophilic ligand enterscell• Often activates gene• !lower response
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9lasma Concentration9lasma Concentration
'lasma concentration of a hormone is influenced by
a. $ormone secretion.
b. 'eripheral hormone conversion. xample T( → T& 9more active:.
c. $ormone transport 9bound or unbound to plasma protein:.
d. $ormone inactivation.•. 'eptide hormones are inactivated by hydrolysis of peptide
bondsD or engulfed and degradaded intracellularly.•. )atecholamines are en=ymatically converted into inactive
forms.•. ?ipophilic hormones are inactivated by alteration of the active
portions, and liver adds charged groups to ma5e them watersoluble.
e. $ormone excretion by liver and 5idneys.
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Hormone ClearanceHormone Clearance
• $ormone must be turned off when served purpose.• 2efines the quantitative removal of hormone from
plasma•
The bul5 of hormone is cleared by liver and 5idneys• Only a small fraction is removed by target tissue• protein and amine hormones bind to receptors and
are internali=ed and degraded•
!teroid and thyroid hormones are degraded afterhormone1receptor complex binds to nuclearchromatin.
• EEF of excreted hormone is degraded or conjugated by'hase I and 'hase II en=yme systems
#eta olic Clearance *ate >#C*?
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#C* /F /#E H/*#/-E#C* /F /#E H/*#/-ET"G% / Time ta5en for half of the dose to be eliminated or metabolised.
Hormone Half-life
Amines 2-3 min
T !roid ormones" T# T3
$% da!s'% ( da!s
Pol!peptides #-#' min
Proteins )(-) ' min
Steroids #-)2' min
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o(n *e+ulationo(n *e+ulation
• @hen the plasma concentration ofhormone is chronically elevated, the
total number of target1cell receptorfor hormone is gradually reduced as adirect result of the effect a sustainedelevation of hormone has on thehormone receptors.
• This phenomenon prevents the targetcells from overreacting to a prolongedhigh concentration of hormone.
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o(n *e+ulationo(n *e+ulationThis down1regulation of the receptors can occur as a result of
". Inactivation of some of the receptor molecule.%. Inactivation of some of the intracellular protein signaling
molecules.
&. Temporary sequestration of the receptor to the inside of thecell, away from the site of action of hormones that interact
with cell membrane receptors.
(. 2estruction of the receptors by lysosomes after they are
internali=ed.*. 2ecreased production of the receptors.
In each case, receptor down1regulation decreases the targettissue’s responsiveness to the hormone.
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Endocrine isordersEndocrine isordersToo Little Hormone Activity Too Much Hormone Activity
• Too little hormone secreted bythe endocrine gland(hyposecretion)*
• Increased removal of the hormonefrom the blood
• Abnormal tissue responsiveness tothe hormone
Lack of target-cells receptorsLack of an enzyme essential tothe target-cell response
• Too much hormone secreted bythe endocrine gland(hypersecretion)*
• educed plasma protein bindingof the hormone (too much free!biologically active hormone)
• "ecreased removal of the
hormone from the blood"ecreased inactivation
"ecreased e#cretion
*$ost common causes of endocrine dysfunction
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yner+ism yner+ism
• !ynergism occurs whenthe actions of severalhormones arecomplementary and theircombined effect isgreater than the sum oftheir separate effects.
• xample C!$ andtestosterone are requiredfor maintaining thenormal rate of spermproduction.
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9ermissi<eness9ermissi<eness
• @ith permissiveness, onehormone must be present inadequate amounts for the fullexertion of another hormone’seffect.
• In essence, the first hormone, by enhancing a target cell’sresponsiveness to anotherhormone, 6permits7 this otherhormone to exert its full effect.
• xample thyroid hormonesincreases the number ofreceptors for epinephrine.
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7nta+onism7nta+onism
• ntagonism occurs whenone hormone causes theloss of another hormone’s
receptors, reducing theeffectiveness of the secondhormone.
• xample progesteroneinhibits uterineresponsiveness to estrogenduring pregnancy, bycausing loss of estrogen
receptors.
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Feed ac! 8oopsFeed ac! 8oops
e+ati<e Feed ac! Controls;-e+ati<e Feed ac! Controls;
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-e+ati<e Feed ac! Controls;8on+ & hort 8oop *e$le@es-e+ati<e Feed ac! Controls;8on+ & hort 8oop *e$le@es
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Endocrine *e$le@ 9ath(ays; /<er<ie(Endocrine *e$le@ 9ath(ays; /<er<ie(
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-euroendocrine *e$le@es-euroendocrine *e$le@es
• 8any endocrine control systemsinvolve neuroendocrine reflexes, which include neural as well ashormonal components.
• The purpose of such reflexes is toproduce a sudden increase inhormone secretion in response to aspecific stimulus, frequently astimulus external to the body.
• Cor example is the increasedsecretion of cortisol, the H7stresshormone7, by the adrenal cortexduring a stress response.
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9rotein and 9olypeptide Hormones9rotein and 9olypeptide Hormones
Hypothalamus
Anterior pituitary
Posterior pituitary
Thyroid
Pancreas
Liver
Parathyroid
• TRH, GnRH, CRH GHRH, Somatostatin,
• ACTH, TSH, FSH, LH, PRL, GH
• Oxytocin, ADH
• Calcitonin
• Insulin,Glucagon,
Somatostatin
• Somatomedin C (IGF-1)
• PTH
Placenta
Kidney
Heart
G.I. tract
Adipocyte
Adrenal medulla
• HCG, HCS or HPL
• Renin
• ANP
• Gastrin, CCK, Secretin, GIP, Somatostatin
• Leptin
• Norepinephrine,epinephrine
*land+Tissue Hormones *land+Tissue Hormones
9rotein and 9olypeptide Hormones;9rotein and 9olypeptide Hormones;
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9rotein and 9olypeptide Hormones;ynthesis and *elease
9rotein and 9olypeptide Hormones;ynthesis and *elease
9rotein and 9olypeptide Hormones;9rotein and 9olypeptide Hormones;
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9rotein and 9olypeptide Hormones;ynthesis and *elease
9rotein and 9olypeptide Hormones;ynthesis and *elease
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• 4inds to surfacereceptor
• Transduction• !ystem activation
• Open ion channel• n=yme activation
• !econd messengersystems
• 'rotein synthesis
9rotein and 9olypeptide Hormone *eceptors9rotein and 9olypeptide Hormone *eceptors
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7mine Hormones7mine Hormones
• 2erived from the amino acid tyrosine
Hypothalamus
Thyroid
Adrenal medulla
• Dopamine
• T 3, T 4
• NE, EPI
*land+Tissue Hormones
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7mine Hormone tructure7mine Hormone tructure
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teroid Hormonesteroid Hormones
Adrenal Cortex
Testes
Ovaries
Corpus Luteum
Placenta
Kidney
• Cortisol, Aldosterone,Androgens
• Testosterone
• Estrogens, Progesterone
• Estrogens, Progesterone
• Estrogens, Progesterone
• 1,25-Dihydroxycholecalciferol
*land+Tissue Hormones
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teroid Hormones; tructureteroid Hormones; tructure
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• re made from cholesterol, are lipophilic < canenter target cell
• re immediately released from cell after
synthesis• Interact with cytoplasmic or nuclear receptors• ctivate 2; for protein synthesis
• re slower acting and have longer half1life thanpeptide hormones
• xamples cortisol, estrogen < testosterone
teroid Hormones; Characteristicsteroid Hormones; Characteristics
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teroid Hormones; 7ctionteroid Hormones; 7ction
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#echanisms o$ action#echanisms o$ action
!teroid < Thyroid hormone mechanisms
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• ndocrine glands throughout body are 5ey tochemical integration and homeostasis
• 'rotein, polypeptide and amine hormones areplasma soluble and target membrane
• !urface receptors transduce signals into cell andactivate via second messengers
ummaryummary
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• 8ost steroid and some amine hormones arelipophilic, can pass into cell, bind on cytoplasmicor nuclear receptors and activate 2; for proteinsynthesis
• $ypothalamus, pituitary trophic hormone
pathways coordinate endocrine regulation
ummaryummary
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Hormones and Their FunctionsHormones and Their Functions
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