Download PowerPoint 演示文稿

The endocrine
system
Introduction
Endocrine system consist of endocrine gland and
endocrine cell.
Hormones :chemical messenger secreted by one
endocrine gland or cell
Classification of the hormones
(1)proteins and polypeptides: insulin, glucagon,
parathyroid
(2)steroids : cortisol, aldosterone, estrogen,
progesterone
(3) derivatives of the amino acid tyrosine
(amine) : thyroxine, E, NE
Characteristics of hormones
(1) they are present in the circulation in low concentrations.
Ranges between pmol and μmol.
(2)every hormones has it’s specific receptor
(3)Interaction

synergism: actions of several hormones are complementary
and their combined effect is greater than the sum of the
separate one

antagonism: one hormone reduce another one’s function

permissiveness: one hormone must be present in adequate
amounts for the full exertion of another hormone’s effect.
Mechanisms of
hormone actions
Hormone receptors and their activation
Types of hormone receptors:
1. In or on the surface of the cell membrane.
2. In the cell cytoplasm.
3. In the cell nucleus
Intracellular signaling after hormone receptor
activation
1. some hormones change membrane
permeability. open channel
2. some hormones activate intracellular enzymes
when they combine with their receptors.
3. some hormones activate genes by binding with
intracellular receptors.
The number of hormone receptors is regulated
The number of receptors in a target cell usually does
not remain constant from day to day, or even from
minute to minute.
down-regulation: decrease production of receptors
Up-regulation: increase production of receptors
Second messenger mechanisms for mediating
intracellular hormonal functions (hydrophilic
hormones)
PIP2: phosphatidylinositol biphosphate
IP3: inositol triphosphate
DAG: diacylglycerol
Hormones that act mainly on the genetic
machinery of the cell (Lipophilic hormones)
1. The steroid hormone enters the
cytoplasm of the cell, where it binds with
a specific receptor protein.
2. The combined receptor protein-hormone
then diffuses into the nucleus.
3. the combination binds at specific sites on
the DNA strands in the chromosomes,
which activates the transcription process
of specific genes to form messenger RNA.
4. The messenger RNA diffuses into the
cytoplasm, where it promotes the
translation process at the ribosomes to
form new proteins.
The pituitary hormones and
their control by the
hypothalamus
The pituitary gland and its relation to the hypo
The pituitary gland has two distinct parts-the anterior
and posterior lobes. The anterior pituitary also known as
the adenohypophysis, the posterior pituitary also known
as the neurohypophysis
Hypothalamic releasing and inhibitory hormones
control anterior pituitary secretion
Major hypophysiotropic hormones
Hormone
effect on the anterior pituitary
thyrotropin-releasing
hormone(TRH)
Corticotropin-releasing
Hormone(CRH)
Gonadotropin-releasing
Hormone(GnRH)
stimulates release of TSH
(thyrotropin) and prolactin
stimulates release of ACTH
(adrenocorticotropic hormone)
stimulates release of LH
(luteinizing hormone) and FSH
(follicle-stimulating hormone)
stimulates release of growth
hormone
inhibits release of growth
hormone
stimulates release of prolactin
inhibits release of prolactin
Growth hormone-releasing
Hormone(GHRH)
Growth hormone-inhibiting
Hormone(GHIH)
Prolactin –releasing hormone(PRH)
Prolactin –inhibiting hormone(PIH)
The anterior pituitary secretes six
established hormones
1.
growth
hormone
(GH),
the
primary
hormone responsible for regulating overall
body
growth,
is
also
important
in
intermediary metabolism.
2.
thyroid-stimulating
stimulating
hormone
hormone
and
growth
(TSH),
of
the
thyroid gland.
3.
adrenocorticotropic
hormone
(ACTH),
stimulates cortisol secretion by the adrenal
4. follicle-stimulating hormone (FSH), has
different function in male and females.
In females it stimulates growth and
development of ovarian follicles, within
which the ova, or eggs develop.
Furthermore, FSH promotes secretion of
the hormone estrogen by the ovaries.
In males FSH is required for sperm
production.
5. luteinizing hormone (LH), in females LH
is responsible for ovulation, luteinization,
and regulation of ovarian secretion of the
female
sex
hormones,
estrogen
and
progesterone. In males the same hormone
stimulates the interstitial cells of Leydig in
the testes to secrete the male sex hormone,
testosterone, giving rise to its alternate
name of interstitial cell-stimulating hormone
(ICSH).
6.
Prolactin
(PRL)
development
females.
and
Its
enhance
milk
function
breast
production
in
in
is
males
uncertain, although evidence indicates
that it may induce the production of
testicular LH receptors. Furthermore,
recent studies suggest that prolactin
may enhance the immune system and
support the development of new blood
vessels
at
the
tissue
level
in
both
sexes- both actions totally unrelated to
its
known
roles
in
reproductive
growth hormone
GH is a small protein molecule that contain
191 amino acids in a single chain. It causes
growth of almost all tissues of the body
that are capable of growing.
1.GH promotes protein deposition in tissues
enhancement of amino acid transport through
the cell membranes enhancement of RNA
translation to cause protein synthesis by the
ribosomes. Increased nuclear transcription of
DNA to form RNA. Decreased catabolism of
protein and amino acids.
2.GH enhances fat utilization for energy
3.GH decreases carbohydrate utilization
4.necessity of insulin and carbohydrate for
the growth-promoting action of hormone.
5.GH stimulates cartilage and bone growth
Regulation of GH secretion
GH is secreted in a pulsatile pattern, increasing and
decreasing.
Stimulate secretion: starvation, hypoglycemia and
low concentration of fatty acids in the blood,
exercise, excitement, trauma
.
GH is also regulated by growth hormone-releasing
hormone and growth hormone inhibitory hormone.
Abnormalities of GH secretion
Dwarfism: lack of GH，
Most instance of
dwarfism result from
generalized deficiency of
anterior pituitary secretion
during childhood.
Gigantism: result
from excessive
GH during childhood.

Acromegaly: result from excessive growth hormone
in adult.
Other hormones besides GH are essential ways for
normal growth:thyroid hormone, insulin, androgens,
estrogens.
The neurohypophysis gland and
its relation to the hypothalamus
Paraventricular nucleus’s and supraoptic
nucleus’s fibers release antidiuretic hormone
and oxytocin which reserve in the
neurohypophysis.
ADH is formed primarily
in the supraoptic nuclei,
whereas oxytoxin is
formed primarily in the
paraventricular nuclei.
Antidiuratic hormone
Acts in kidney to regulate water
balance and control blood pressure
Oxytocin
Function:
(1)oxytocin causes contraction of the
pregnant uterus
(2)oxytocin aids in milk ejection by the
breasts
Regulation of oxytocin release

Oxytocin secretion is increased by reflexes
that originate within the birth canal during
childbirth.

Milkejection reflex: Oxytocin secretion is
increased by reflexes that are triggered
when the infant suckles the nipple.
These reflexes also be called neurohumoral
reflex.

Psychological and emotional factors, such as
fear, may inhibit the release of oxytocin.

Anxiety,pain and sympathoadrenal
stimulation release oxytocin

alcohol inhibits its secretion.
The thyroid hormones
The thyroid gland secrets two
significant hormones:
thyroxine(T4)
triiodothyronine (T3).
Raw material of thyroid synthesis :
iodine and thyroglobin. Iodine combine
with thyroglobin produce T4 and T3.
The TH are stored in the follicles in
an amount sufficient to supply the
body with its normal requirements of
TH for 2 to 3 months.
T4 secretion > T3 secretion
T4 converted to T3 in most tissues,
especially liver and kidney
T3 is more active hormone than T4.
On entering the blood, over 99 per cent of
the T4 and T3 combines immediately with
thyroxine-binding globulin, thyroxinebinding prealbumin, albumin.
Physiological functions of the
thyroid hormones
1.TH increase cellular metabolic activity.
The basal metabolic rate can increase
60 to 100 per cent above normal. when
large quantities of the hormones are secreted.
.
TH increase the number and activity of
mitochondria. Increase the rate of formation
of ATP, increase activity of the cell.
Thyroid hormones increase active transport
of ions through cell membranes. The activity
of sodium –potassium ATPase increases.
2. Effect of TH on growth
Skeletal growth : promotion of
skeletal maturation
3.Promote growth and development of
the brain during fetal life and for the
first few years of postnatal life.
Lack of thyroid hormone after birth
and without therapy with thyroid
hormones, this disease is called
“cretinism”. Failure of body growth
and by mental retardation.
4. Effects of TH on specific bodily
mechanisms
(1)stimulation of carbohydrate metabolism
(2)stimulation of fat metabolism
(3)increased requirement for vitamins.
(4)increased basal metabolic rate
(5)decreased body weight
5. Effects of TH on the cardiovascular
system
(1)increased blood flow and cardiac output.
(2)increased heart rate
(3)increased heart strength
6. Increased gastrointestinal motility,
increased respiration
7. excitatory effects on the CNS
slightly increase in TH, makes the
muscles react with vigor, excessive
hormone, because of excess protein
catabolism, muscles become sluggish.
8. effect on sleep, other endocrine
glands
Difficult to sleep, insulin increase.
Regulation of TH secretion
TH is regulated by the
hypothalamus-pituitary-thyroid
axis.
If lack of iodine in food, T3 and
T4 synthesis decrease, the
inhibition of TSH is free, TSH
is higher than normal condition,
the thyroid gland is enlargement.
(endemic goiter)
Stress,cold
hypothalamus
—
thyrotropin-releasing
Hormone(TRH)
＋
pituitary
thyroid-stimulating
Hormone(TSH)
＋
thyroid gland
Thyroid hormone
T3 T4
—

thyroid-stimulating hormone (TSH)
stimulating hormone and growth of the
thyroid gland.
Diseases of Thyroid Gland
Hyperthyroidism = overactive thyroid
Increased metabolic rate
Enlargement of thyroid gland (goiter)
Weight loss, nervousness, irritability
Intolerance to heat
Bulging eyeballs
Hypothyroidism = underactive thyroid
Slowed metabolic rate, fatigue,
weight gain Cretinism, if present
and untreated at birth
The adrenocortical hormones
The adrenal gland: Paired glands;
located on top of kidneys
Each adrenal gland has two
parts
Medulla Inner portion
Synthesizes/secretes E
and NE
(stress hormones)
Cortex
Outer portion
Cortex
zona reticularis: sex
hormone, and rogens
(dehydroepiandrosterone
DHEA), estrogen
zona glomerulosa:
mineralocorticoids
(aldosterone)
zona fasciculata:
glucocorticoids (cortisol,
corticosterone)
Functions of the mineralocorticoids
-aldosterone
Aldosterone
Regulates Na+ and K+ balance ; promotes Na+
reuptake in kidney
Deficiency of aldosterone : wasting of sodium
chloride and hyperkalemia
Excess aldosterone : causes hypokalemia and
muscle weakness
Functions of the
glucocorticoids-hydrocortisol
1. It stimulates hepatic gluconeogenesis
into carbohydrate within the liver.
2. It inhibits glucose uptake and use by
many tissues, but not brain. It can
increase blood glucose concentration.
3. It stimulates protein degradation in
many tissues, especially muscle.
4.It facilitates lipolysis, the
breakdown of lipid stores in
adipose tissue, thus releasing
free fatty acids into the blood.
5.Permissive actions cotisol
strengthen the vasoconstriction
of NE.
6.Role in adaptation to stress
Resistance to Stress. When an animal or
human is exposed to a wide variety of
noxious stimuli, there is an increased
secretion of ACTH and consequently rise in
the circulatory glucocorticoid level. This
rise is essential for survival. Noxious stimuli
that increase the ACTH secretion is called
“stressor”. The reason that an elevated
circulatory glucocorticoid level is essential
for resisting stress remains for the most
part unknown.
Regulation of cortisol secretion by adrenocorticotropic
hormone from the pituitary gland
Diseases of Adrenal Glands
Cushing’s Disease
–hyperactive adrenal cortex
–rounded face & obesity
–Thin, frail skin; poor wound healing
Addison’s Disease = adrenal cortex
insufficiency
–Decreased appetite, weight loss
–Cold intolerance
–Stress susceptibility
pancreas
(1)the
acini, which secrete digestive juices
into the duodenum
(2)the islets of Langerhans, which secret
insulin and glucagon into the blood.
Insulin and its metabolic effects
Insulin is secreted by beta cells in islets
of Langhans.
Functions:
Insulin lowers blood glucose, amino acid, and fatty
acid levels. promote the synthesis of protein, fat
and glucogen.
It causes fat storage in the adipose tissue. All the
excess carbohydrates that can not be stored as
glycogen are converted into fats stored in the
adipose tissue.
In the case of proteins, insulin has a direct in
promoting amino acid uptake by cells and
conversion of these amino acids into protein.
Regulation of insulin
1.The primary stimulus for increased insulin secretion is an increase in blood
glucose concentration . An elevated blood glucose level directly stimulates
synthesis and release of insulin by the beta cells
2. An elevated blood amino acid level directly stimulates beta cells to increase
insulin secretion.
3.the major gastrointestinal hormones secreted, the insulin increase.
4.the parasympathetic nerve stimulate insulin release, on the contrary, the
sympathetic nerve inhibit insulin release.
Diabetes:lack of insulin
glucagon and its function
A hormone secreted by alpha cells of the islets of
Langerhans
Functions:
Breakdown of liver glycogen and increased
gluconeogenesis in the liver, therefore increase
glucose concentration.
Regulation of glucagon
increased blood glucose inhibits glucagon secretion.
Increased blood amino acids stimulate glucagon
secretion.
Endocrine control of
calcium
and metabolism
Extracellular fluid calcium concentration
normally is 2.4 mmol/L.
Calcium metabolism is regulated by
parathyroid hormone (PTH),
vitamin D
calcitonin.
 Parathyroid
(PTH)
hormone
Secreted by parathyroid gland respond to reduced
blood calcium levels.
Function:
1. PTH stimulate osteoclast to remove Ca2+ from the
bone matrix and inhibit osteoblast from making
new bone.
2. Kidney: PTH increased Ca2+ reabsorption, PO42excretion.
Regulation of PTH
Fall in plasma Ca2+ concentration, the PTH increase .
Calcitonin
Produced by the C cells of the thyroid
gland.
Function
It suppression of osteoclast bone
absorption reducing plasma Ca2+ and PO42-.
Regulation
Concentration of Ca2+ increased ,The
calcitonin increased.
Vitamin D
Vitamin D is obtained from the diet or
synthesized by the skin as a result of
irradiation of 7-dehydrocholesterol by
ultraviolet rays from the sun. Circulating
Vitamin D is first hydroxylated in liver to
yields 25-hydroxycholecalciferol, further
hydroxylation in the kidney yields the active
form, 1,25- dihydroxycholecalciferol.
Function of Vitamin D
Promotes intestinal calcium and
phosphate absorption.
Deceases renal calcium and phosphate
excretion.
All in all, it can coordinate with PTH
increase Ca 2+ .