Download 2-3 endocrine sys Sp12

Body control systems

Endocrine system
Endocrine system
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Controls body
activities by
releasing
hormones
Slower responses
Broader influence
Hormones are carried by the
blood to target cells
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Endocrine glands
release hormones
into bloodstream
Hormones are
carried to all cells of
the body, but only
affect certain cells
Regulate the
metabolism of target
cells
Hormones alter activities of cells in
different parts of the body
Endocrine
cell
How do hormones know which
cells to communicate with?
Membraneenclosed
sacs
Blood
vessel
Hormone
molecules
Hormone
Receptor
Target cell
Adrenal glands
(type of endocrine
gland), which sit
atop the kidneys
Receptor
protein
Each hormone has a
receptor that fits it like
a key into a lock.
“Target Cells”
Target cells have receptors
for particular hormones.
Figure 25.1
How do hormones travel to
target cells?
In the blood!
Why do hormones only affect
certain cells?
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Water soluble hormones:
Dissolved in blood
Hormones only affect target cells, cells that
have receptors for that specific hormone
Target cell
Receptor
protein
Lipid soluble hormones:
Attached to transport proteins
(blood is watery, so fat soluble chemicals
can’t mix well on their own)
Steroid Hormone
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Hormones have a wide range
of targets
There are two main classes of
hormones
Some, like sex hormones, affect most of the tissues
of the body
Others, like glucagon, have only a few target cells
(in this case, liver and fat cells)
Some target other endocrine glands
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Peptide hormones
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the pituitary targets the ovaries, testes, thyroid gland
Most common type of hormone
Short chains of amino acids
Water soluble, circulate in a “free” form
(not attached to plasma proteins)
Some hormones have different responses in
different target cells
Copyright 2009, John Wiley &
Sons, Inc.
There are two main classes of
hormones
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There are two main classes of
hormones
Steroid hormones
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The main difference is their solubility
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Fat-soluble
Can diffuse thru cell
membranes
Bind to transport
proteins in blood
Peptide hormones
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Steroid hormones
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Steroid Hormone
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water-soluble
cannot penetrate the cell membrane
lipid-soluble
pass directly through the phospholipid bilayer of cell
membranes
This single difference translates into
completely different modes of action
Action of steroid hormones
Action of peptide hormones
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1. Hormone binds to a
receptor in the plasma
membrane.
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Hormone binds to a
receptor in the
plasma membrane
Activates a second
messenger in the
target cell
Alters cell functions
peptide hormone
1.
receptor protein
2.
2. Binding leads to
activation of an
enzyme that changes
ATP to cAMP .
plasma
membrane
ATP
3.
cAMP
(second messenger)
3. cAMP activatesan
enzyme cascade.
4. Many molecules of
glycogen are broken
down to glucose,
which enters the
bloodstream.
glucose
(leaves cell
and goes
to blood)
glycogen
Action of glucagon on liver
steroid
hormone
1. Hormone diffuses
through plasma
membrane because
it is lipid soluble.
capillary
4.
Diffuse thru
membrane
Bind to receptors
inside target cells
The hormone-receptor
complex binds to the
DNA and alters gene
expression
New proteins are
made → changes the
cell’s activity
plasma
membrane
cytoplasm
nucleus
2. Hormone binds
to receptor inside
nucleus.
protein
DNA
receptor
protein
mRNA
3. Hormone-receptor
complex activates
gene and synthesis
of a specific mRNA
molecule follows.
ribosome
mRNA
4. mRNA moves to
ribosomes, and protein
synthesis occurs.
Mechanism of action:
Estrogen
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Estrogen binds to
estrogen receptors in
the cell nucleus
Switches on/off
transcription of specific
genes
Hormones need tight controls
Most hormones are
released in short bursts
Hormone secretion is
controlled by
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1. Signals from the nervous
system
TSH
2. Changes in blood chemicals
(glucose, calcium)
3. Other hormones
Most hormone secretion is
regulated by negative
feedback
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“Master” endocrine glands:
the hypothalamus and pituitary
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Hypothalamus – major link
between nervous and
endocrine system
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The hypothalamus
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Hypothalamus and pituitary
secrete hormones
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These hormones regulate
all aspects of growth,
development, metabolism,
and homeostasis
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Copyright 2009, John Wiley &
Sons, Inc.
The pituitary
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Infundibulum
(stalk)
It controls secretion of
hormones by the pituitary
gland
Copyright 2009, John Wiley &
Sons, Inc.
The posterior pituitary is
actually an extension of the
hypothalamus
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Anterior
pituitary
Receives information from the
nervous system
Secretes hormones
Anterior pituitary hormones
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Posterior
pituitary
Is the main control center of
the endocrine system.
Integrates nervous and
endocrine control
Human growth hormone (hGH)
It stores and secretes
hormones made in the
hypothalamus
Acts in water regulation and
childbirth
The anterior pituitary
secretes 7 hormones which
in turn stimulate other
endocrine glands
Thyroid stimulating hormone (TSH)
Infundibulum
Anterior
pituitary
Follicle stimulating hormone (FSH)
Luteinizing hormone (LH)
Prolactin (PRL)
Adrenocorticotropic hormone (ACTH)
Melanocyte-stimulating hormone (MSH)
Human Growth Hormone (hGH)
Human growth hormone
↑ Growth of bones & muscles
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Has a broad effect on the body
Causes cells in liver, muscles,
bones and other tissues to
grow and multiply
Increases breakdown of fat in
adipose tissue
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Immune System
Stimulated
Breakdown of stored
nutrients
(ex. release of sugars to
blood)
Numerous growth diseases
involve hGH
Low hGH 
Pituitary Dwarfism
Releases fatty acids for ATP
production
High hGH in Childhood
 Gigantism
Hormones regulate the rate of
metabolism
High hGH in Adulthood
 Acromegaly
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Thyroxine (T3/T4)
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Secreted by the
thyroid gland
Increases the
metabolic rate
hGH
Insulin
In adults, arm/leg bones have finished
growing, but facial bones can be
stimulated to grow more
Regulation of T3 and T4
secretion
Thyroxine
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Secreted by the
thyroid
Thyroid produces
thyroid hormones
 T4 = Thyroxine
 T3 = Triiodothyronine
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Both stimulate cell
metabolism
Copyright 2009, John Wiley &
Sons, Inc.
1 Low blood levels of T3
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and T 3 or low metabolic
rate stimulate release of
Low blood T3/T4 or low
metabolic rate
Hypothalamus
TRH
2 TRH, carried
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Release of TRH
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Release of TSH
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Synthesis of T3 and T4
by thyroid gland
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↑ T3/T4 in blood
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Negative feedback
by hypophyseal
portal veins to
anterior pituitary,
stimulates
release of TSH
by thyrotrophs
5 Elevated
T3inhibits
release of
TRH and
TSH
(negative
feedback)
TSH
3 TSH released into
blood stimulates
thyroid follicular cells
Anterior
pituitary
4 T3 and T4
Thyroid
follicle
released into
blood by
follicular cells
Thyroid Gland Disorders:
hypothyroidism
Actions of T3/T4
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Affect most body cells
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If have receptors for thyroid
hormones
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Increased metabolism
Growth and development
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Stimulate protein synthesis
Increase use of glucose and fatty
acids for ATP production
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Why does the thyroid gland
enlarge?
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X
Congenital
hypothyroidism during
fetal life or infancy →
severe mental retardation
(cretinism)
Excess thyroid hormones
The most common form of
hyperthyroidism is Graves’
disease
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X
enlargement of the thyroid
gland
Hyperthyroidism
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X
Too little thyroid hormone
Due to dietary deficiency
of iodine or from a
defective thyroid gland
Sx: Goiter
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an autoimmune disease.
Produce antibodies that
mimic the action of TSH and
continually stimulate the
thyroid gland
Sx: enlarged thyroid,
protruding eyes
(exophthalmos)
Copyright 2009, John Wiley &
Sons, Inc.
The pancreas has a dual role
Blood glucose homeostasis
Insulin
Glucagon
It secretes
• digestive enzymes
• hormones insulin & glucagon
regulate body’s energy supplies
Pancreatic Beta cells secrete
insulin
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Insulin
Regulation of Blood Glucose
After a meal, blood
sugar levels rise
Pancreas secretes
insulin
Insulin lowers blood
sugar by stimulating
liver, muscle and fat
cells to take up
glucose
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Glucagon is a
peptide hormone
It binds to receptors
on the membrane of
target cells
Supplies energy to the brain and
active muscle
Insulin and glucagon have
opposite effects
Why does glucagon stimulate
liver and not stomach cells?
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When blood glucose levels are
low, the pancreas secretes
glucagon
Glucagon stimulates liver and
muscle cells to break down
stores of glycogen, releasing
glucose into the blood
Glucagon increases blood
sugar between meals
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Target cell
Receptor
protein
Both insulin and
glucagon regulate
the body’s energy
supplies
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Insulin
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Glucagon
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↓ blood sugar levels
↑ blood sugar levels
Copyright 2009, John Wiley &
Sons, Inc.
How insulin stimulates glucose
uptake
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Glucose
transporters
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In the absence of insulin,
only a few glucose
transporters are on the
cell surface
Insulin binds to its
receptor
Insulin recruits glucose
transporters from inside
the cell to the cell surface
Glucose is transported
into cells
Pancreatic Disorders
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Diabetes mellitus is a common
and serious impairment of
glucose homeostasis
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the body loses control of the level
of glucose in the blood
One of the most serious chronic
diseases in the US
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$92 billion a year in health care
costs
~7% of the U.S. population has
diabetes
The sixth leading cause of death
Type I Diabetes
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Insulin and type 1 diabetes (4:03)
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Type 2 diabetes
Autoimmune disease
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Destroys cells that make
insulin
Most common form
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Occurs most often in
children and young adults
The patient must monitor the
level of glucose in the blood
and inject insulin when it
climbs
Complications: damage to
blood vessels in retina and
kidneys
Rx: insulin injections
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Insulin resistance
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90% of diabetics
55% are obese
Cells don’t respond to insulin
Can’t absorb glucose
properly
Can be controlled by diet,
exercise and weight loss
http://www.youtube.com/watch?v=OYvav8aDGCc
Gestational diabetes
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Calcium Homeostasis
Pregnant women who have
never had diabetes before
but who have high blood
glucose levels during
pregnancy
Affects about 4% of all
pregnant women
It may precede development
of type 2 diabetes
Calcitonin and PTH have opposing
actions
These hormones
have opposite
effects on blood
calcium levels
Calcitriol
(vitamin D)
Figure 25.10
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Three hormones
regulate blood
calcium levels
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Calcitriol
(vitamin D)
Calcitonin
Parathyroid hormone
(PTH)
Calcitriol (vitamin D)