Transcript The Endocrine System and Homeostasis

The Endocrine System
and Homeostasis
Two types of glands
ENDOCRINE
GLANDS
Hormones are secreted
directly into the
bloodstream, which
transports the
hormones throughout
the body.
Examples include:
pituitary and adrenal
glands
EXOCRINE
GLANDS
• are glands that secrete their
products (hormones) into
ducts
• Examples include sweat,
salivary, mammary glands
and the many glands of the
digestive system.
Chemical Signals regulate homeostasis
HORMONES are chemical messengers which “excite” or “set in motion” a
series of reactions.
TWO TYPES OF HORMONES:
• Lipid Soluble: these hormones can easily diffuse through
the lipid bilayer of cell membranes. This interaction
activates specific genes, causing changes in the cell.
EXAMPLES: Steroid hormones, such as testosterone,
estrogen, and cortisol.
• Water Soluble (protein or protein-related hormones):
these hormones cannot diffuse across the cell membrane.
EXAMPLES: Epinephrine, human growth hormone,
thyroxine, and insulin.
Negative Feedback Loops
Once the hormone’s
message has been
delivered, enzymes
inactivate the
hormone – thus
causing a NEGATIVE
FEEDBACK LOOP.
Main regulatory gland
is the Hypothalamus.
United Streaming video: Endocrine System – Biologix –
Hypothalamus/Pituitary gland – Video Segment #2
Example: Affects on Blood Pressure
 In the example to the right
blood pressure has
increased.
 Therefore, receptors in
the carotid arteries detect
the change in blood
pressure and send a
message to the brain.
 The brain will cause the
heart to beat slower and
thus decrease the blood
pressure.
DECREASING HEART RATE HAS A NEGATIVE EFFECT ON
BLOOD PRESSURE.
The MASTER gland:
The Pituitary
Gland secretes at least
eight hormones.
Involved in the body’s
metabolism, growth,
development, reproduction
and other critical life
functions.
Hypothalamus
Controlled by the
hypothalamus – secretes
only 2 hormones – directs
activities of other glands.
The two lobes are called
the anterior and posterior
gland -- each lobe is a
separate gland and they
release different hormones
Pituitary Gland
United Streaming: Endocrine System –
Biologix: Hypothalamus/Pituitary –
Segment #4
Anterior Pituitary Gland
Anterior pituitary: hormonesynthesizing
it’s cells produce and release six major
hormones, including:
hGH
PRL
TSH
ACTH
FSH
LH
Human Growth
Hormone (hGH)
• Stimulates the liver to
secrete growth hormones
called growth factors.
• Protein synthesis
• Cell division and growth
• Metabolic breakdown and
release of fats stored in
adipose tissue
• Stimulates the growth of
muscles, connective tissue
and the growth of plates at
the end of long bones.
Disorders caused
by hGH
GIGANTISM – is a
disorder caused by
excessive amounts of
hGH during childhood.
DWARFISM – low
amount of hGH
ACROMEGALY – after
reaching adulthood,
overproduction of hGH
THYROID GLAND
Hormone, thyroxine produced in the thyroid
Regulates body metabolism and the growth and
differentiation of tissues.
Individuals who secrete higher levels of thyroxine oxidize
sugars and other nutrients at a faster rate.
Lower levels of thyroxine do not break down sugars as
quickly.
Excess blood sugar is eventually converted into liver and
muscle glycogen. Unfortunately, if blood sugar is too high,
the excess sugar is converted to fat.
Hypothyroidism – low thyroid secretions
Hyperthyroidism – high thyroid secretions
Goiters - Thyroid Gland disorder
CRETINISM causes very
serious retardation of physical
and mental development; if the
condition is left untreated,
growth is stunted and the
physical stature attained is that
of a dwarf.
GRAVES DISEASE symptoms
may include:
Anxiety
Irritability
Difficulty sleeping
Fatigue
A rapid or irregular heartbeat
A fine tremor of your hands or
fingers
An increase in perspiration
Sensitivity to heat
Weight loss, despite normal food
intake
Brittle hair
Enlargement of your thyroid
gland (goiter)
Light menstrual periods
Frequent bowel movements
Parathyroid gland
Functions of the Parathyroid and
PTH (parathyroid hormone)
Maintenance of the body's calcium level
When blood calcium levels drop below a certain
point, calcium-sensing receptors in the
parathyroid gland are activated to release
hormone into the blood.
Parathyroid hormone has effects antagonistic to
those of calcitonin. It increases blood calcium
levels by stimulating bone cell breakdown and,
thus, the release of calcium.
Calcitonin
Calcitonin, produced in the thyroid gland, has the
ability to decrease blood calcium levels at least in
part by effects on two well-studied target organs:
Bone: Calcitonin suppresses reabsorption of bone
calcium
Kidney: Calcium and phosphorus are prevented
from being lost in urine by reabsorption in the
kidney tubules. Calcitonin inhibits tubular
reabsorption of these two ions, leading to
increased rates of their loss in urine.
THE
ADRENAL
GLANDS
• Two adrenal
glands located
above the kidney
• Composed of an
inner layer
(adrenal medulla)
and an outer layer
(adrenal cortex)
Adrenal Medulla
SHORT TERM
RESPONSES
• Considered a neuroendocrine structure
• produces two closely
related hormones
(epiniphrine and
norephinephrine)
• Flight or fight
response by
increasing metabolism
ADRENAL CORTEX
Long Term Stress Response
• Glucocorticoids increase
blood sugar
• Mineralocorticoids
increase pressure
• Gonadocorticoids, female
and male sex hormones,
supplement the
hormones produced by
the gonads
CORTISOL – glucocorticoid which is regulated by
the anterior pituitary and the adrenal glands
It has several functions including:
– helps to regulate blood pressure.
– helps to regulate the immune system.
– helps to balance the effect of insulin to keep the blood sugar
level normal.
– helps the body to respond to stress.
Aldosterone
Mineralcorticoid
Stimulates the distal and collecting tubules of the
kidneys to increase the absorption of sodium into
the bloodstream.
This increases the solute concentration of the
blood, which then draws in more water from the
nephrons, raising blood pressure.
Addison’s disease can result, if the adrenal
cortex is damaged. In this case, the body
secretes inadequate amounts of
mineralocorticoids and glucocorticoids.
THE PANCREAS (exocrine
gland)
Exocrine – means
this gland
secretes its
products through
ducts
Pancreas contains two types of cells: digestive enzymes
and hormones.
Islets of Langerhans – produce insulin and glucagon
(both hormone producing)
INSULIN
Regulation of blood sugar
Insulin is produced in the beta cells
of the islets of Langerhans and is
released when the blood sugar level
is high.
Insulin increases glucose utilization
by making many cells of the body
permeable to glucose.
Glucagon – produced in the alpha cells
and works with insulin
Released when blood sugar levels are
low.
Promotes the conversion of glycogen to
glucose. As glycogen is converted to
glucose in the liver, the blood sugar level
returns to normal.
Other hormones, such as hGH, cortisol,
and epinephrine also contribute to
increasing the level of blood glucose.
Insulin causes a decrease in blood sugar level, and
glucagon causes an increase in blood sugar level.
The effects of glucose
imbalance
Diabetes Mellitus
• Hyperglycemia: high
blood sugar
• Without insulin, cells
remain relatively
impermeable to glucose
and cannot obtain enough
from the blood.
The loss of glucose in the
urine causes the osmotic
gradient across the
nephrons of the kidneys.
Large volumes of water
therefore follow the
glucose.
Untreated people with
diabetes mellitus
experience low energy and
great thirst (SHORT
TERM).
LONG TERM: can lead to
blindness, kidney failure,
nerve damage and
gangrene in the limbs.
Two types of diabetes mellitus
Type 1 diabetes
Type 2 diabetes
• Juvenile and/or insulindependent diabetes
• Immune system produces
antibodies that attack and
destroy the beta cells of
the pancreas.
• The beta cells degenerate
and are unable to produce
insulin.
• Develops gradually
because the insulin
receptors on the body’s
cells stop responding to
insulin.
• Also, another way, the
beta cells of the pancreas
produce less and less
insulin over time.
• People who are overweight
have a greater chance of
developing type 2
diabetes.
Posterior Pituitary Gland
Considered part of the nervous
system
DOES NOT PRODUCE HORMONES
Hypothalamus, produces, ADH
and oxytocin—posterior pituitary
stores them for use