BAI GIANG VE HE NOI TIET (Endocrine System)

Endocrine system
After studying this chapter, students are able to know:
−the difference between endocrine and neural control
− different types of intercellular chemical signals and signallings
− to differentiate between endocrine and exocrine glands
− Hormones, chemical classes of hormones define their properties: Hormonetarget cell interactions. Signal transduction pathways triggered by hormones
−Hormone-receptor interaction
− Membrane-bound receptors for lipophobic hormones
− signal transduction pathways with the 2nd messenger system: cAMP,c GMP, IP3, DAG, Ca2+

− intracellular receptors for lipophilic hormones and the regulation of gene
expression and protein synthesis
−The main endocrine glands/ tissues /structures in human
− The hypothalamus-pituitary-target gland axis and negative feedback control of
endocrine glands
−Hypothalamus and neurohormones
− Pituitary gland and its hormones
−Thyroid gland and thyroid hormones. The synthesis of thyroid hormones, the role
of iodine in the synthesis of thyroid hormones. Hyper-and hypothyroidism
− Parathyroid gland and the role of its hormones in regulating blood calcium
concentration.
−Adrenal gland, corticosteroid hormones and catecholamines
− Pancreas gland. Insulin, glucagon and diabetes mellitus
− Sex hormones and functions


Specific terms and keywords
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Endocrine
Endocrine glands/exocrine gland
Endocrinology
Hormone
Hormone synthesis
Hormone release/secretion
Receptor
Hormone-receptor interaction
Target cells
Signal transduction pathway


Endocrine system and nervous system - the two
main control systems in the body
• The endocrine system, together with the nervous system, work to
control and coordinate the cells to accomplish physiological activities
and function of animals
• The endocrine system works differently from how the nervous
system does:
Neural control
electrical signal and chemical signals fast
-

-

Endocrine control
chemical signals (hormones)
slow , longer lasted

Rõ ràng, chính xác

-

precisely targeted (neural signals
are precisely targeted)

-

controls predominantly the fine, rapid movements of discrete muscles

Phần lớn, chủ yếu là

•

-

broadcast (endocrine signals are broadly
distributed throughout the animal’s body)
controls more widespread, prolong activities
(e.g.metabolic changes)

The nervous system and the endocrine system can control one another

Endocrine signal is one type of intercellular chemical
signals

Autocrine signal

Neurohormone

Paracrine signal

Neurotransmitter

Endocrine signal

Pheromone

www.copewithcytokines.de/cope.cgi?key=Autocrine



Endocrine and Exocrine glands

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Hormone and its properties
• Hormone is a chemical substance produced and released by
endocrine cells or by neurons. It regulates function of distant
cells reached via the blood
• Hormones are chemical messengers transporting signal
from one cell to another -> they convey information from

cells to cells
• Hormone is effective at very low concentration (e.g.for
insulin: 1IU= 0.0347 mg
• Hormones are secreted by secretory cells into extracellular
fluid, from which they diffuse into capillaries and the
circulation. They travel in the blood to reach distant target
cells/ tissues expressing specific receptors
• Hormones trigger cascade effect in the target cells


hormonal signal is amplified by
hormonal cascade effects

C.L. Standfield.2011. Principles of Human Physiology, 4th edition.


Hormone interactions
One hormone can target different cell types -> can produce more
than one effect in the body (eg. ADH affects epithelial cells in the
kidneys (increasing water reabsorption) and smooth muscle cells of
some blood vessels (causing vasoconstriction of these vessels)
One body function is regulated by more than one hormone (eg.
Blood Ca2+ is controlled by calcitonin, PTH, vitamin D3; blood
glucose by insulin, glucagon, epinerphrine, cortisol, GH)
If the effects of 2 hormones oppose each other: antagonism
process
If 2 or more hormones produce the same type of response, the
effect can be addictive (net effect equals the sum of individual
effects) or synergistic (net effect is greater than the sum of
individual effects)

If the presence of one hormone is needed for another hormone
to be effective: permissiveness process (e.g. thyroid hormone
stimulates beta adrenergic receptor expression needed for
epinephrine to be effective on smooth muscle cells of bronchioles
(dilating bronchioles)
Sửù co maùch

choỏng choùi, phaỷn ủoỏi


Chemical classification of hormones
Amino acids

Glutamate, aspartate, glycine, gamma-aminobutyric
acid (GABA)

hydrophilic, lipophobic

Amines

Catecholamines: dopamine, norepinephrine,
epinephrine (tyrosine derivatives)
Thyroid hormones (tyrosine derivatives)
Serotonine (tryptophan derivatives)
Histamine (histidine derivatives)

hydrophilic, lipophobic

Peptides/
Proteins

GH, Prolactin, Insulin / Thyrotropin releasing
hormon, oxytocin, ADH, calcitonin, glucagon, ACTH,
endorphin, MSH, Hormon của hypothalamus,
lipotropin, somatostatin

Hydrophilic, lipophobic

Glycoprotein FSH, LH,TSH,PTH
Steroids

Estrogen
Progestin (progesterone)
Testosterone
Mineralocorticoid
Glucocorticoid

Hydrophobic, lipophilic

Fatty acid

Derivativatives of arachidonic acid: prostaglandins,
leukotriens, thromboxanes

Hydrophobic, lipophilic

Properties of
hormones
depend mainly
on whether they

are lipophilic or
lipophobic


The synthesis of peptide/protein hormones

Fig. 5.4 C.L. Standfield.2011. Principles of Human Physiology, 4 th edition.


C.L. Standfield.2011. Principles of Human Physiology, 4th edition.


The release and transport of hormone in blood

• H-Pr <-> H + Pr

C.L. Standfield.2011. Principles of Human Physiology, 4th edition.


Hormone – target cell interaction


Properties of receptors
• Specificity: a receptor
binds only one hormone/
messenger or a class of
messengers
• The binding between a
hormone and a receptor is a
brief, reversible chemical

interaction.
• Affinity: the strength of the
binding between a
messenger and its receptor
C.L. Standfield.2011. Principles of Human Physiology, 4th edition.


Hormone signal transduction pathway

1. signal reception
2. signal transduction
3. response of the target cell
fig.cox.miami.edu/~cmallery/150/memb/cellcomm.htm


Receptor agonist and receptor antagonist

• Agonists: ligands that bind to receptors and
produce a biological response
• Antagonists: ligands that bind to receptors
but do not produce a biological response
• Antagonists may compete with agonists for
the receptor, blocking or decreasing the
effects of agonists on target cells
application in drug design and drug
target


Location of receptors in target cells
•

•

Location of receptors in target cells depends on
whether the messenger/hormone is lipophilic or
lipophobic
membrane bound receptor
– Lipophobic/hydrophilic hormones
– large hormone molecules
– Modes of action:
1. regulate channel-linked receptor
2. activate intracellular enzymes by phosphorylation
3. activate G protein

•

intracellular receptor
– receptors in cytosol or in the nucleus of target cells
– Lipophilic (lipid-solube) hormones


Fast ligand-gated calcium channels

Fig. 5.13 C.L. Standfield.2011. Principles of Human Physiology, 4 th edition.


enzyme-linked receptor
• The receptor and the enzyme
(mainly tyrosine kinase) are
the same protein
• H-R changes enzyme

conformation-> activate
tyrosine kinase ->
phosphorylation of intracellular
proteins-> cellular responses
– Insulin
– GH
– Prolactin
– Growth factors

C.L. Standfield.2011. Principles of Human Physiology, 4th edition.


Channel - linked receptor

•fast channel: receptor and
channel are the same protein
−Acetylcholin: Na+ (excitatory)

−Serotonin: Na+ (excitatory)
−Glutamat: Na+ (excitatory)
−Glycine: Cl- (inhibitory)

−GABA: Cl-

C.L. Standfield.2011. Principles of Human Physiology, 4th edition.

(inhibitory)


G-proteine-linked receptor

• 7 transmembrane domains
• Extracellular side binds to
hormone/ligand
• Intracellular side binds
G-protein(GDP)
• When inactivated:Gprotein: α, β, γ; α –GDP
• When activated: α –GTP
moves to the effectors
changing effectors activity
• Effectors: ion channels
(slow ligand gated ion
channels) or enzymes
•
Slow ligand-gated ion channel

Fig.5.15 C.L. Standfield.2011. Principles of Human Physiology, 4th edition.

3 main types of G proteins:
–
–
–

G-Proteins affecting ion channels
stimulatory G protein (Gs protein)
inhibitory G protein (Gi protein)


Gs and Gi proteins activate and inhibit, respectively, enzymes
(amplifier enzymes) catalyzing the production of 2nd messengers

•

2nd messengers:
–
–
–
–
–

cAMP (cyclic AMP)
cGMP (cyclic GMP)
Inositol triphosphate (IP3)
Diacyglycerol (DAG)
Ca2+


H- G-protein R -> Adenylate cyclase-> cAMP ->
protein kinase A

Earl W. Sutherland (Nobel Prize - 1971)
cAMP: epinephrine
glucose

C.L. Standfield.2011. Principles of Human Physiology, 4th edition.

fig.cox.miami.edu/~cmallery/150/memb/cellcomm.htm


cGMP
• H- G protein R-> guanylate cyclase->

cGMP -> protein kinase G