Copyright 2010. PEER.tamu.edu
 How have you changed over the
past year?
 What has caused those
changes?
 How do you think you will
change in the next few years?
 The Endocrine System
regulates, coordinates and
controls:




Growth and development.
Male and female development.
How your body uses energy.
Levels of salts and sugars in
your blood.
 The amount (volume) of fluid in
your body.
 Appetite.
 Many other body functions.
 The Endocrine
Glands are the
organs of the
Endocrine System.
 They produce and
secrete (release)
Hormones.
 They are located all
over your body.
Gland
What it Regulates
Pituitary
“Master Gland” that regulates all other
Endocrine Glands, also releases growth
hormone
Thyroid
Metabolism, body heat, bone growth
Parathyroids
Use of Calcium and Phosphorous
Hypothalamus
Links nervous system to endocrine system
Adrenal
Response in emergency or stressful
situations, metabolism, blood pressure, salt
balance
Pancreas
Blood sugar
Ovaries
Production of eggs; female characteristics
Testes
Production of sperm; male characteristics
Thymus
Parts of the immune system
 The answer is
Hormones!
Hormones are chemical
messengers that are secreted
(released) from glands into the
blood and affect cells in another
part of the body.
 Hormones only work on certain cells, called
target cells.
 The target cells have special receptors that
“recognize” the hormones and allow them to
influence that cell.
Target
Target Cell
Cell for
for
Hormone
Hormone A
A
Target Cell for
Hormones A and B
Hormone A
Target Cell for
Hormone B
Hormone B
These receptors recognize the hormones.
They “fit” like a lock and key.
External stimuli
by way of nerves
from the sensory
organs in the nervous
system
Internal stimuli
by way of nerves
and other hormones
from inside the body
Brain reacts by way
of secretions from
neurons in
hypothalamus
(neurohormones)
Brain also reacts by
way of nerves from
hypothalamus and
brainstem
“Autonomic Nervous System”
What is the
difference between
nerve and hormone
control?
Why both kinds
of controls?
Discuss your answers.
•Remember, external means coming from
outside of your body and internal means
coming from inside of your body.
Stimulus:
 You hear a loud noise
 A large dog runs toward you,
growling and barking
 You eat a large candy bar
 You have not eaten in six hours
 You have strep throat
 A chain of events occur that lead from the
stimulus to the response.
 Negative feedback means that when
enough hormone is in the body, the
body stops producing the hormone
until it is needed again.
You eat. Glucose (sugar)
in the blood increases.
Increased glucose is detected by receptors
that notify the brain. It sends a message
to the pancreas to produce insulin.
Pancreas stops making insulin.
Blood glucose level drops as
it is removed by the cells.
Insulin tells muscle and liver to take up
glucose from the bloodstream and use it for energy
or store it for later. Brain reduces appetite.
Diabetes
In the case shown in this picture, the body produces insulin but the target cells become
resistant and unresponsive to it. Diabetes can also be caused by the body not
producing enough insulin. The glucose does not enter the muscle and liver cells like it
should and it builds up in the blood causing complications.
A few hormone systems
are positive feedback
systems:
The pituitary gland sends a
signal by way of the
hormone oxytocin to the
uterus causing contractions.
The pressure of the fetus on
the cervix sends a signal
back to the brain which
then stimulates the release
of more oxytocin. This
causes more contractions.
The fetus pushes harder on
the cervix. More oxytocin
is released. The system
continues until birth occurs.
 When normal functions lose their negative feedback
control, many times disease is the result.
 An example:
•Neurons in the hypothalamus secrete thyroid releasing
hormone (TRH), which stimulates cells in the anterior
pituitary to secrete thyroid-stimulating hormone (TSH).
•TSH binds to receptors to cells in the thyroid gland,
stimulating thyroid hormones, which affect all cells in
the body.
•When blood concentrations of thyroid hormones
increase above a certain level, TRH-secreting neurons
in the hypothalamus are inhibited and stop secreting
TRH.
•If this process is disrupted, the Thyroid keeps
producing hormones and hyperthyroid disease ensues.
Do you know where each hormone comes from, where it acts, and
what the action is? Guess first, then click each to find out.
Progesterone
Insulin
Adrenaline
Testosterone
Thyroxine
Cortisol
Estrogen
Done
 Where it comes from: Adrenal
Gland
 Where it acts: heart, blood
vessels, eyes
 What it does: stimulates heart
rate, increases blood pressure,
dilates pupils
 Causes "Adrenaline Rush”
 A 'fight and flight' hormone.
 It is released in high stress
conditions or in excitement or
fear.
 Loud noise, high temperature
etc. may also trigger its
release since these are also
high stress situations.
Return to hormones slide
• Where it comes from:
ovary (where an egg
was released)
• Where it acts: uterus
• What it does: controls
menstruation in
women and plays a
role in pregnancy.
• One of the
components of birth
control pills
Return to hormones slide
 Where it comes from:
thyroid gland
 Where it acts: most cells of
the body
 What it does: controls the
rate of metabolic processes
(how energy is used) in the
body and influences
physical development
 People may not produce
enough of this hormone and
get a condition known as
hypothyroidism. They can
take thyroxine to treat this
condition.
Return to hormones slide
 Where it comes from: testicles
 Where it acts: body-hair cells,
muscle, reproductive structures
 What it does: stimulates
development of male sexual
characteristics
 Testosterone is a steroid and has
been administered to athletes in
order to improve performance.
This is considered to be a form
of doping in most sports and is a
very dangerous practice.
 Females also produce small
amounts of testosterone in their
ovaries that affect muscle
development and other body
Return
functions.
to hormones slide
 Where it comes from: ovary
 Where it acts: breast tissue,
reproductive structures in
female
 What it does: stimulates
development of female
sexual characteristics
 Estrogen levels may be
related somehow to
migraine headaches in
women.
Return to hormones slide
 Where it comes from:
outer part of adrenal
gland
 Where it acts: multiple
tissues
 What it does: mental
stimulation, breaks down
fat and protein to
glucose, antiinflammation
 It is usually referred to
as the "stress hormone"
as it is involved in
response to stress and
anxiety.
Return to hormones slide
 Where it comes from:
Insulin is produced in the
pancreas
 Where it acts: liver,
muscle, and fat tissue
 What it does: Insulin
causes cells to take up
glucose (sugar) from the
blood, storing it in the
liver and muscle, and
stopping use of fat as an
energy source.
 Problems with insulin
production or use in the
body can lead to
diabetes.
Return to hormones slide
 What are the functions of the Endocrine
System?
 Name 5 Endocrine Glands and what they do.
 What are hormones?
 How do hormones work?
 Name some hormones and what they do.
 At what times in your life do you think your
Endocrine System is most active?