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Title: science
Description: Contains and explains lots of areas of medical science involving the human body
Description: Contains and explains lots of areas of medical science involving the human body
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The Endocrine System
Dr
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, publishing as Benjamin Cummings
Endocrine System
The endocrine system interacts with the nervous
system to coordinate and integrate body activities
by means of hormones
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Exocrine tissues, such as salivary glands, and
sebaceous glands, secrete chemical substances
through ducts into an open space
...
, publishing as Benjamin Cummings
Five major functions of hormones
a) Regulate metabolic processes (e
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thyroid hormones)
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g
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c) Aid in the transport of substances across the cell
membrane of target cells (e
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insulin and glucagon)
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g
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e) Play a vital role in reproduction, growth and
development (e
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estrogens , progesterone, and
testosterone)
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, publishing as Benjamin Cummings
Major Endocrine Organs
Copyright © 2006 Pearson Education, Inc
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fat – insoluble; as a result cannot diffuse across the membrane of target
cells
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b) Steroid hormones: made of fatty acids using cholesterol as a
functional group
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only hormones secreted by the gonads and adrenal cortex belong to this
group
...
, publishing as Benjamin Cummings
Hormone Action
1
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c) Hormone diffuses into capillaries
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e) Hormone diffuses out of capillaries at target
tissue, and causes an effect in target cells
...
, publishing as Benjamin Cummings
Thyroid Gland
Copyright © 2006 Pearson Education, Inc
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Each step of this action plan is highly specific and
carefully controlled by the endocrine and circulatory
systems :
synthesis of hormone using protein or lipid anabolism
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transport of hormone in the blood or lymph (i
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steroid hormones require a “protein transporter”
during the transport)
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e
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Copyright © 2006 Pearson Education, Inc
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Effects in the target cells caused by hormone action
a
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g
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b
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g
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c
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g
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d
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g
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Copyright © 2006 Pearson Education, Inc
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Steroid hormones bind to a protein transporter during the
transport in blood of lymph
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When they have arrived at the target cells , the protein
transporter (being fat-insoluble) is repelled by the cell membrane,
while the steroid hormone (being fat-soluble) diffuses into the
cytoplasm of target cell
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Steroid hormone also diffuses across the nuclear envelope and
enters into the nucleus of target cell
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Steroid hormone binds to a specific receptor located on a
particular gene of target cell’s DNA
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This binding alters the genetic information within that gene,
resulting in a new messenger RNA (mRNA) being produced after
transcription
...
, publishing as Benjamin Cummings
6
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7
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Copyright © 2006 Pearson Education, Inc
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Endocrine glands secrete steroid hormone
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Steroid hormone diffuses through target cell membrane
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Hormone combines with a receptor molecule
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steroid hormone-receptor complex binds to DNA and promotes
synthesis of mRNA
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mRNA enters the cytoplasm and directs protein synthesis
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Newly synthesized protein produce hormone’s specific effects
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The new protein causes a specific effect to occur within the target
cells
...
, publishing as Benjamin Cummings
Steroid Hormones
Copyright © 2006 Pearson Education, Inc
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A protein hormone is transported in the blood or lymph by itself,
without a transporter
...
When it has arrived at the target cell, the protein hormone binds
with a specific receptor embedded in the cell membrane of target
cell
...
3
...
Copyright © 2006 Pearson Education, Inc
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The product of these reactions is a substance known as the
“secondary messenger” (usually cyclic adenosine monophosphate
or cAMP), which acts on behalf of the protein hormone , causes a
potent effect in the target cell (usually within the cytoplasm)
...
Since protein hormones never diffuse to the DNA of target cells,
no new proteins or enzymes are made at the end
...
, publishing as Benjamin Cummings
Sequence of protein hormone action - summary
1
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2
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3
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4
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5
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6
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7
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8
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Copyright © 2006 Pearson Education, Inc
...
, publishing as Benjamin Cummings
Control of hormone secretion
I
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b) hormones that are secreted by endocrine glands and travel to target
cells directly are called nontropic hormones
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g
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d) most hormones travel a long distance and act on target cells, they are
called circulating (or endocrine) hormones; while other hormones
travel a short distance, they are called local (paracrine) hormones
...
, publishing as Benjamin Cummings
II
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g
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b) Hormone release at the posterior pituitary gland is
controlled by nerve fibers from the hypothalamus
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g
...
Copyright © 2006 Pearson Education, Inc
...
, publishing as Benjamin Cummings
Major endocrine glands & hormones
The pituitary gland: attached to the hypothalamus by infundibulum
...
Anterior lobe is about 3 times larger than
posterior lobe
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Anterior pituitary is under hormonal control by the hypothalamus
where blood vessels transport “releasing hormones” to the anterior
lobe
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Somatotrophs produce GH
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Corticotrophs produce ACTH and MSH
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Gonadotrophs produce FSH and LH
...
, publishing as Benjamin Cummings
Relationship of the pituitary gland & Hypothalamus
Copyright © 2006 Pearson Education, Inc
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posterior pituitary is under nervous control by the hypothalamus
where nerve fibers innervate the posterior lobe for its release of
hormones (posterior pituitary does not produce hormones; it only
release hormones made by the hypothalamus)
...
, publishing as Benjamin Cummings
Anterior pituitary gland – 7 hormones
Growth hormone (GH) -- for normal growth and
development of all body cells, especially muscle
and bone cells
...
Thyroid-stimulating hormone (TSH) -- stimulates
the thyroid gland to secrete thyroid hormones
...
Copyright © 2006 Pearson Education, Inc
...
, publishing as Benjamin Cummings
Adrenocorticotropic hormone (ACTH) – stimulates the
adrenal cortex to secrete mineralocorticoids, glucocorticoids,
or gonadocorticoids
...
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[Hypersecretion causes no known
effects, while hyposecretion can cause failure of sexual maturation]
Luteinizing hormone (LH) -- triggers ovulation and stimulates the
production of estrogens and progesterone in female, and promotes
testosterone production in male
...
Prolactin (PRL) or Lactogenic hormone (LTH) -- stimulates milk
production in the mammary glands
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Melanocyte-stimulating hormone (MSH) -- stimulates melanocytes
in the epidermis and hair follicles to release melanin pigment
...
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[Disorders are
rare and have no known effects, except in some
hyposecretion cases, weak labor contraction is
reported]
...
[Hypersecretion
has no know effects, and hyposecretion causes
frequent urination called diabetes insipidus]
...
, publishing as Benjamin Cummings
Thyroid gland
a) located inferior to the larynx (voice box) and attached to the trachea
...
c) thyroid follicles utilize iodine and synthesize thyroglobulin (TGB) to
be stored in the colloids
...
[Hyposecretion causes hypothyroidism, similar to
cretinism and myxedema, and hypersecretion causes hyperthyroidism
that results in a goiter or in Graves’ disease]
...
[Both hyposecretion and
hypersecretion would affect normal balances of calcium and
phosphate]
...
, publishing as Benjamin Cummings
Synthesis of thyroid hormone
Copyright © 2006 Pearson Education, Inc
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Secrete only 1 protein
hormone called
parathyroid hormone
(PTH) or parathormone
to raise blood calcium
level and lower blood
phosphate level
...
Copyright © 2006 Pearson Education, Inc
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Adrenal Cortex: outer portion of the adrenal gland
which is attached to the superior surface of the kidney
...
Secretes over 30 steroid-based substances and several steroid
hormones, all crucial for normal homeostasis
...
Aldosterone is the most important hormone
in this group, where it raises blood levels of sodium and
water, and lowers blood potassium level
...
, publishing as Benjamin Cummings
Adrenal gland
Copyright © 2006 Pearson Education, Inc
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Cortisol is the most important
hormone in this group, where it is involved in carbohydrate,
lipid and protein metabolism , and also helps fight stress and
inflammation
...
Zona reticularis secretes gonadocorticoids which supplement
sex hormones from the testes and ovaries and stimulate early
development of reproductive organs
...
Copyright © 2006 Pearson Education, Inc
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Adrenal Medulla: inner portion of the adrenal gland
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Contains glandular cells called chromaffin cells which secrete 2
closely related hormones -- Epinephrine (or adrenaline) and
Norepinephrine (or noradrenaline)
...
[No known effects are due to hyposecretion of these,
but hypersecretion can caused hypertension, increased blood
glucose level , and high heart rate]
...
, publishing as Benjamin Cummings
Pancreas
The only gland that is both exocrine and endocrine in physiology
...
In its endocrine aspect, 1% of its mass is little groups of cells called
islets of langerhans (or pancreatic islets) which secrete hormones to
regulate blood glucose level
...
beta cells (β cells) secrete insulin to lower blood glucose level
...
Copyright © 2006 Pearson Education, Inc
...
, publishing as Benjamin Cummings
delta cells (δ cells) secrete somatostation or growth hormone
inhibiting hormone (GHIH) which helps regulate
carbohydrate metabolism by inhibiting the secretion of
glucagons
...
, publishing as Benjamin Cummings
Ovary
The female sex organ that also serves as an endocrine gland
...
[Both hyposecretion and hypersecretion will have
broad effects in female reproduction]
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[Discorders are
similar to those for estrogens]
...
, publishing as Benjamin Cummings
Testis
The male sex organ that also serves as an endocrine gland
...
[Both hyposecretion and hypersecretion and will have broad
effects in male reproduction]
...
-- secrets melatonin to regulate circadian rhythms which are
necessary to keep track of day/night cycles, sleep/wake
rhythm, menstrual and ovarian cycles
...
, publishing as Benjamin Cummings
Thymus gland: A diminishing gland (over time) located
between the lungs
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Heart : The organ for pumping blood in the cardiovascular
system
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Digestive organs: stomach secretes hormones such as
gastrin to stimulate stomach activities
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-- secrete a hormone called Erythropoietin to
stimulate red blood cell production in the red bone
marrow
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-- secretes estrogen and progesterone to maintain
normal pregnancy
...
, publishing as Benjamin Cummings
Major events in the general stress syndrome
1
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2
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, blood glycerol conc
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, heart rate, blood pressure , and breathing
rate
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3
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4
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ACTH stimulates release of Cortisol by the adrenal cortex
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Cortisol increases the conc
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7
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8
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9
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Pituitary increases
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ADH promotes the retention of H2O by the kidneys, which
increases blood volume
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Renin increases blood level of angiotnsin II, which acts as a
vasoconstrictor and also stimulates Aldosterone secretion by the
adrenal cortex
...
Copyright © 2006 Pearson Education, Inc
...
, publishing as Benjamin Cummings
The control pathway of Cortisol
Copyright © 2006 Pearson Education, Inc
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Hyperthyroidism : High metabolic rate, sensitivity
to heat, restless ness, hyperactivity, weight loss ,
protruding eyes , goiter
...
, publishing as Benjamin Cummings
Hypothyroid :
Hashimoto’s disease : Auto antibodies (against self) attack
thyroid cells, producing hypothyroidism
...
Hypothyroidism (adult) : Myxedema - low metabolic rate,
sensitivity to cols, sluggishness, poor appetite , swollen tissue
, mental dullness
...
Copyright © 2006 Pearson Education, Inc
...
, publishing as Benjamin Cummings
Disorders f the parathyroid glands
I
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cause : Tumor
Treatment : Remove Tumor , correct bone deformities
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Hypoparathyroidism : muscle cramps and seizures
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cause : inadvertent surgical removal; injury
...
Copyright © 2006 Pearson Education, Inc
Title: science
Description: Contains and explains lots of areas of medical science involving the human body
Description: Contains and explains lots of areas of medical science involving the human body