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The Endocrine System
By Alex Shih
State Standards

Students know how feedback loops in the nervous and
endocrine systems regulate conditions in the body.
 Students know how hormones (including digestive, reproductive,
osmoregulatory) provide internal feedback mechanisms for
homeostasis at the cellular level and in whole organisms.
First Look
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The endocrine system is composed of glands that release hormones into the
bloodstream, affecting the activities of other cells.
Glands are tubeless organs or group of cells that directly secrete hormones into
the bloodstream.
Uses blood vessels as information channels
Animation
What Are Hormones?
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Hormones are chemicals that travel through the bloodstream and bind
to specific chemical receptors on cells. These cells with receptors for a
particular hormone are called target cells.
Hormones act as messengers, broadcasting messages from the
endocrine system.
Regulate mood, growth and development, tissue function, and
metabolism
Influences physical and mental responses.
For example, hormones produced during puberty cause physical
changes in the body.
Hormones are dissolved in the
blood plasma
System Functions and Jobs
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The endocrine system is regulated by feedback mechanisms that
function to maintain homeostasis- maintain a stable internal
environment
To control metabolism the hypothalamus secretes a hormone called
TRH, which stimulate the pituitary gland to secrete TSH, which
stimulates the release of thyroxine by the thyroid gland. Thyroxine
affects the metabolism of the body
To maintain water balance, the hypothalamus signals the pituitary gland
to release more or less of the antidiuretic hormone (ADH). This
hormone tells the kidneys to either slow down or fasten the removal of
water.
Animations
Organs/Glands of the Endocrine System
Hypothalamus
Makes hormones that control the pituitary
gland
Pituitary gland
Produces hormones that regulate other
endocrine glands
Pineal gland
Releases melatonin
Thyroid
Produces thyroxine, regulating metabolism
Parathyroid gland
Four glands; release parathyroid hormone,
regulating the level of calcium in blood
Thymus
Releases thymosin, simulating T cell
development in childhood
Adrenal glands
Releases epinephrine and norepinephrine to
cope with stress
Pancreas
Produces insulin and glucagon, regulating the
level of glucose in blood
Ovary (female)
Testis (male)
Produces estrogen and progesterone
Produce testosterone
Pituitary Gland
Bean-sized
structure
thatgland
dangles
a slender
stalk of tissue
at the For
A•malfunction
in the
pituitary
can on
trigger
life threatening
conditions.
baseif of
the
skull (bit
smaller
than atoo
green
pea)
example
the
pituitary
gland
produces
much
growth hormone or too little,
• Divided
two parts:
anterior pituitary and the posterior pituitary
gigantism
andinto
dwarfism
canthe
result.
• Overall the two parts work together and the whole gland produces and
discharges nine hormones that directly regulate many body functions
control many other components of the endocrine system
• Functions List: Anterior: growth hormone, stimulate the ovaries or
testes, prolactin, and stimulate adrenal and thyroid glands; Posterior:
control skin pigmentation, absorption of water into the blood, and
stimulate milk production
Hypothalamus
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Attached to the posterior pituitary
Controls the secretions of the
pituitary gland
The endocrine system and the
nervous system interact at the
hypothalamus; allow the two
systems to work together
For addition functions of the
hypothalamus click here
Thyroid Gland
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Main job: regulate the body’s metabolism by
producing thyroxine
Also secretes calcitonin- hormone that
decreases the level of calcium in blood
The activities of the thyroid gland are usually
well controlled
Hyperthyroidism might result if the thyroid gland
produces too much thyroxine- increased
metabolic rates
Hypothyroidism= low production of thyroxinelow metabolic rates
Parathyroid Gland
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There are four parathyroid glands
found on the back surface of the
thyroid gland
PTH (parathyroid hormone)
maintain homeostasis in blood
calcium levels.
The hormone regulates the calcium
levels in the blood by increasing the
reabsorption of calcium in the
kidneys and also by directing the
uptake of calcium from the digestive
system
This gland is important for bring
about healthy nerve and muscle
function and bone structure
Adrenal Glands
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Two pyramid-shaped structures that sit on top of the kidneys, one on
each kidney.
These glands help the body to make preparations for and dealing with
stress
Adrenal gland has two parts: Adrenal cortex (outer part), adrenal
medulla (inner part)
The adrenal cortex is responsible for producing about 24 hormones
named cortico-steroids. An example of this would be the hormone
cortisol, which helps control the rate of metabolism of carbohydrates,
fats, and proteins
The adrenal medulla releases two hormones called epinephrine and
nonepinephrine, effecting the response to stress
Pancreas
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Releases insulin and glucagon to
keep the level of glucose in the
blood stable
•If
pancreas
• the
Insulin
removedoes
sugarnot
from blood
produce
enoughtells
insulin,
then
and glucagon
the liver
to break
diabetes
mellitus occurs- the
down glycogen
amount
of glucose
in the
• It is located
adjacent
rightblood
and
behind extremely
to the stomach
becomes
high so that
the
kidneys
excrete
glucose
in
• Part
of both
the digestive
and
systems, therefore,
the endocrine
urine
separated into two portions
• The endocrine portion is a clutter of
cells located in the islets of
Langerhans, which releases
hormones
Gonads: Ovary & Testis
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Female: Ovary; Male: Testis
The gonads produce gametes and
secrete sex hormones
Ovaries produce eggs and testis
produce sperm
Secretion of sex hormones
controlled again by the pituitary
gland
Hormones list- females: estrogen &
progesterone; males: testosterone
For More Information…
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Internet Link #1
Internet Link #2
Internet Link #3
The End