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7/17/2019 fisiologi endokrin-hipothalamus-gigi-BMS1-2015.pdf
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© 2012 Pearson Education, Inc.
SistemEndokrihipothalam
C h a p t e r
18
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Tujuan Pembelajaran
1. Menjelaskan Struktur kelenjar endokrin
2. Menjelaskan fungsi hormon
3. Menjelaskan hormon hipothalamus
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An Introduction to the Endocrine System
• The Endocrine System
•
Regulates sort-medium-term processes
• Metabolism
• Regulates long-term processes
• Growth
• Development
• Reproduction
• Uses chemical messengers to relay information and instructions
between cells
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18-10 Hormone Interactions
• The Effects of Hormones on Behavior
• Hormone changes
• Can alter intellectual capabilities, memory, learning,
and emotional states
• Affect behavior when endocrine glands are over-
secreting or under-secreting
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Hormone Interactions
• The Hormonal Responses to Stress
• General Adaptation Syndrome (GAS)
• Also called stress response
• How body responds to stress-causing factors
• Is divided into three phases
1. Alarm phase
2. Resistance phase
3. Exhaustion phase
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Production of ADH, oxytocin, andregulatory hormones
Anterior lobe:
ACTH, TSH, GH, PRL, FSH, LH,and MSH
Posterior lobe:
Release of oxytocin and ADH
(located on the posterior surfacthe thyroid gland)
Parathyroid hormone (PTH)
Melatonin
Hypothalamus
Pituitary Gland
Parathyroid Glands
Pineal Gland
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Thyroid Gland
Thyroxine (T4)Triiodothyronine (T3)Calcitonin (CT)
Adrenal Glands
Adrenal medulla:
Epinephrine (E)Norepinephrine (NE)
Adrenal cortex:
Cortisol, corticosterone,
aldosterone, androgens
InsulinGlucagon
Pancreas (Pancreatic Islets) Testis
Ovary
Thymus: (Undergoes atrophy
during adulthood)Secretes thymosins
Adipose Tissue: Secretes• Leptin
Digestive Tract: Secretesnumerous hormones involved in thecoordination of system functions,glucose metabolism, and appetite
Kidneys: Secrete• Erythropoietin (EPO)
• Calcitriol
Gonads: Testes (male):
Androgens (especially testosterone),inhibin
Ovaries (female):
Estrogens, progestins, inhibin
Organs with SecondaryEndocrine Functions
Heart: Secretes natriuretic peptides.• Atrial natriuretic peptide (ANP) • Brain natriuretic peptide (BNP)
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18-2 Hormones
• Classes of Hormones
•
Hormones can be divided into three groups1. Amino acid derivatives
2. Peptide hormones
3. Lipid derivatives
• Secretion and Distribution of Hormones
• Hormones circulate freely or travel bound to special
carrier proteins
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18-2 Hormones
• Amino Acid Derivatives
•
Are small molecules structurally related to aminoacids
• Derivatives of Tyrosine:
• Thyroid hormones
• Catecholamines
• Epinephrine, norepinephrine
• Derivatives of Tryptophan:
• Dopamine, serotonin, melatonin
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18-2 Hormones
• Peptide Hormones
•
Are chains of amino acids• Most are synthesized as prohormones
• Inactive molecules converted to active hormones
before or after they are secreted
• Glycoproteins
• Proteins are more than 200 amino acids long and havecarbohydrate side chains
• Thyroid-stimulating hormone (TSH)
• Luteinizing hormone (LH)
• Follicle-stimulating hormone (FSH)
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18-2 Hormones
• Peptide Hormones
•
Short Polypeptides/Small Proteins• Short chain polypeptides
• Antidiuretic hormone (ADH) and oxytocin (OXT)(each 9 amino acids long)
• Small proteins
• Growth hormone (GH; 191 amino acids) and
prolactin (PRL; 198 amino acids)
• Includes all hormones secreted by:
• Hypothalamus, heart, thymus, digestive tract,pancreas, and posterior lobe of the pituitary gland,as well as several hormones produced in otherorgans
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18-2 Hormones
• Lipid Derivatives
• Eicosanoids - derived from arachidonic acid, a 20-carbon fatty acid
• Paracrine factors that coordinate cellular activitiesand affect enzymatic processes (such as bloodclotting) in extracellular fluids
• Some eicosanoids (such as leukotrienes) havesecondary roles as hormones
• A second group of eicosanoids - prostaglandins -involved primarily in coordinating local cellularactivities
• In some tissues, prostaglandins are converted tothromboxanes and prostacyclins, which alsohave strong paracrine effects
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18-2 Hormones
• Lipid Derivatives
• Steroid hormones - derived from cholesterol
• Released by:
• The reproductive organs (androgens by the testes in males
estrogens and progestins by the ovaries in females)
• The cortex of the adrenal glands (corticosteroids)
•
The kidneys (calcitriol)• Because circulating steroid hormones are bound to specific tra
proteins in the plasma:
• They remain in circulation longer than secreted peptide ho
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18-2 Hormones
• Secretion and Distribution of Hormones
•
Free Hormones• Remain functional for less than 1 hour
1. Diffuse out of bloodstream and bind to receptors on target
2. Are broken down and absorbed by cells of liver or kidneys
3. Are broken down by enzymes in plasma or interstitial fluid
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18-2 Hormones
• Secretion and Distribution of Hormones
•
Thyroid and Steroid Hormones• Remain in circulation much longer because most are “bound”
• Enter bloodstream
• More than 99% become attached to special transport prote
•
Bloodstream contains substantial reserve of bound hormon
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18-2 Hormones
• Mechanisms of Hormone Action
•
Hormone Receptor• Is a protein molecule to which a particular molecule binds stron
• Responds to several different hormones
• Different tissues have different combinations of receptors
•
Presence or absence of specific receptor determines hormonalsensitivity
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18-2 Hormones
• Down-regulation
•
Presence of a hormone triggers decrease in number ofhormone receptors
• When levels of particular hormone are high, cells become
less sensitive to it
• Up-regulation
• Absence of a hormone triggers increase in number of
hormone receptors
• When levels of particular hormone are low, cells become
more sensitive to it
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18-2 Hormones
• Hormones Receptors
•
Catecholamines and Peptide Hormones • Are not lipid soluble
• Unable to penetrate plasma membrane
• Bind to receptor proteins at outer surface of plasma membrane
(extracellular receptors)
• Eicosanoids
• Are lipid soluble
• Diffuse across plasma membrane to reach receptor proteins on in
surface of plasma membrane (intracellular receptors)
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18-2 Hormones
• Hormones and Plasma Membrane Receptors
• First and Second Messengers
• Bind to receptors in plasma membrane
• Cannot have direct effect on activities inside target cell
• Use intracellular intermediary to exert effects
18 2 H
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18-2 Hormones
• First Messenger
• Leads to second messenger
• May act as enzyme activator, inhibitor, or cofactor
• Results in change in rates of metabolic reactions
18 2 H
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18-2 Hormones
• Important Second Messengers
1. Cyclic-AMP (cAMP)
• Derivative of ATP
2. Cyclic-GMP (cGMP)
• Derivative of GTP
3. Calcium ions
18 2 H
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18-2 Hormones
• G Protein
• Enzyme complex coupled to membrane receptor
• Involved in link between first messenger and second
messenger
• G Proteins and cAMP
• Adenylate cyclase is activated when hormone binds
to receptor at membrane surface and changes
concentration of second messenger cyclic-AMP
(cAMP) within cell
• Increased cAMP level accelerates metabolic activity
within cell
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Hormone
Proteinreceptor
G proteinactivated
Hormone
Proteinreceptor
G proteinactivated
Effects on cAMP Levels
Many G proteins, once activated, exert their effects by changing the concentrationof cyclic-AMP, which acts as the second messenger within the cell.
Increasedproductionof cAMP
adenylate
cyclase Acts assecond
messenger
kinase
Activatesenzymes
Opens ionchannels
If levels of cAMP increase,
enzymes may be activated
or ion channels may be
opened, accelerating the
metabolic activity of the cell.
Examples: • Epinephrine and norepinephrine
(β receptors)
• Calcitonin
• Parathyroid hormone
• ADh, ACTH, FSH, LH, TSH
• Glucagon
Examples: • Epinephrine and norepineph-
rine (α2 receptors)
In some instances, G protein
activation results in decreased
levels of cAMP in the
cytoplasm. This decrease has
an inhibitory effect on the cell.
Enhancedbreakdown
of cAMP PDE
Reduced
enzymeactivity
Hormone
Proteinreceptor
G protein(inactive)
G proteinactivated
18 2 H
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18-2 Hormones
• G Proteins and Calcium Ions
• Activated G proteins trigger:
• Opening of calcium ion channels in membrane
• Release of calcium ions from intracellular stores
• G protein activates enzyme phospholipase C (PLC)
• Enzyme triggers receptor cascade
• Production of diacylglycerol (DAG) and inositoltriphosphate (IP3) from membrane phospholipids
• May further activate more calcium ion channels through
protein kinase C (PKC)
• Calcium ions may activate calmodulin which causes fu
cellular changes
18 2 Hormones
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18-2 Hormones
• Hormones and Intracellular Receptors
•
Alter rate of DNA transcription in nucleus• Change patterns of protein synthesis
• Directly affect metabolic activity and structure of
target cell
•Include steroids and thyroid hormones
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Receptor
Diffusion throughmembrane lipids
CYTOPLASM
Target cell response
Alteration of cellularstructure or activity
Translation andprotein synthesis
Binding of hormoneto cytoplasmic ornuclear receptors
Transcription andmRNA production
Gene activation
Binding ofhormone –receptorcomplex to DNA
Nuclearpore
Nuclearenvelope
Receptor
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Receptor
Receptor
Target cell response
Alteration of cellularstructure or activity
Translation andprotein synthesis
Transcription andmRNA production
Gene activation
Binding ofhormone –receptorcomplex to DNA
Binding of receptorsat mitochondria andnucleus
Transport acrossplasma membrane
Increased
ATP
production
18 2 Hormones
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18-2 Hormones
• Control of Endocrine Activity
• The hypothalamus provides highest level of endocrine control
• In most cases, controlled by negative feedback mechanisms
• Stimulus triggers production of hormone, the direct or
indirect effects of the hormone reduce intensity of the
stimulus
18 2 Hormones
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18-2 Hormones
• Hormone Release
• Can be triggered by:
1. Humoral stimuli
• Changes in composition of extracellular fluid
2. Hormonal stimuli
• Arrival or removal of specific hormone
3. Neural stimuli
• Arrival of neurotransmitters at neuroglandular
junctions
P d ti f ADH C t l f th tiSecretion of reg lator
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Production of ADHand oxytocin
HYPOTHALAMUS
Control of sympatheticoutput to adrenalmedullae
Secretion of regulatoryhormones to control activityof the anterior lobe of thepituitary gland
Preganglionicmotor fibers
Adrenal gla
Secretion of epinephrineand norepinephrine
Adrenal medulla
Adrenal cortex
Posterior lobeof pituitary gland
Release of ADHand oxytocin
Hormones secreted by the anteriorlobe control other endocrine organs
Anterior lobeof pituitary gland
Infundibulum
18-3 The Pituitary Gland
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18-3 The Pituitary Gland
• Hypothalamic Control of the Anterior Lobe
• Two classes of hypothalamic regulatory hormones
1. Releasing hormones (RH)
• Stimulate synthesis and secretion of one or more
hormones at anterior lobe
2. Inhibiting hormones (IH)
• Prevent synthesis and secretion of hormones from
anterior lobe
• Rate of secretion is controlled by negative feedback
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Endocrinetargetorgan
Hormone 2(from targetorgan)
TRH
CRH
GnRH
TSH
ACTH
FSH
LH
Thyroidgland
Adrenalcortex
Ovaries
Testes
Thyroidhormones
Gluco-corticoids
Inhibin
Inhibin
Estrogens
Progestins
Estrogens
Androgens
Releasinghormone(RH)
Hormone 1(frompituitary)
Ovaries
Testes
Negative feedback
Hypothalamus
RH
Pituitarygland
Anteriorlobe
Hormone 1
Endocrine
organ
Hormone 2
Target cells
KEY
Stimulation
Inhibition
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Stimulatesmammaryglands
Liver
Epithelia,adipose tissue,liver
Stimulates growth of skeletal muscle,cartilage, and many other tissues
Stimulation
Inhibition
Stimulation
Inhibition
Anteriorlobe
Anteriorlobe
Somatomedins
GH –IH
GH –RH
GH PRL
PRF
PIH
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Hypothalamic releasing hormones
Hypothalamic releasing
hormone
Effect on pituitary
Corticotropin releasing hormone(CRH) Stimulates ACTH secretion
Thyrotropin releasing hormone
(TRH)
Stimulates TSH and Prolactin
secretion
Growth hormone releasing
hormone (GHRH)
Stimulates GH secretion
Somatostatin Inhibits GH (and other
hormone) secretionGonadotropin releasing
hormone (GnRH)
Stimulates LH and FSH
secretion
Prolactin releasing hormone
(PRH)
Stimulates PRL secretion
Prolactin inhibiting hormone
(dopamine)
Inhibits PRL secretion
Characteristics of hypothalamic releasing hormone
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Characteristics of hypothalamic releasing hormone
• Secretion in pulses
• Act on specific membrane receptors
• Transduce signals via second messengers
• Stimulate release of stored pituitary hormones
• Stimulate synthesis of pituitary hormones
• Stimulates hyperplasia and hypertophy of target cells
• Regulates its own receptor