Download hormones - Avon Community School Corporation

Turn in 2.3.1 Feedback Loop &
completed Conclusion ?s
Keep Part III Body Graphic
Organizer for 2.3.2
Endocrine System PPT
Activity 2.3.2 Hormones Gone Wild
Pt. 1
Groups of 4=Maniken Partner
& Pair up with another Group
Pineal
Parathyroid
Pancreas
Pituitary
Adrenal
Thyroid
Thymus
Ovaries
Testes
10. Hypothalamus
THE ENDOCRINE SYSTEM
What is the Endocrine System?
o Communication system for the body
o Secretes hormones – chemical
messengers
o These hormones regulation of growth,
metabolism, sexual development, and
emotions
o Internal balance of body systems =
homeostasis by working with the nervous
system
o Specifically the hypothalamus
Endocrine Glands
o Ductless
oMeaning: the hormone that is
secreted goes into the blood stream
directly to a target cell/tissue.
o Major Endocrine Glands
o
o
o
o
o
o
o
o
o
o
Pituitary Gland
Hypothalamus
Thymus
Pineal Gland
Testes
Ovaries
Thyroid
Parathyroid
Adrenal Glands
Pancreas
Exocrine Glands
o They have ducts
ocarries secretions to external locations of the
body
oExamples
o sweat glands
o salivary glands
o mammary glands
o stomach
o liver
o pancreas
Hormones
o HORMONES
are chemical MESSENGERS
that act on target cells or organs.
Classes of Hormones
o
Steroid Hormones
o Sex hormones – lipids made from cholesterol
o Testosterone, Estrogen
o
Amino Acid Derivative Hormones
o Derived from amino acids – tyrosine and
tryptophan
o Epinephrine
o
Peptide Hormones
o Made of chains of amino acids
o Most numerous
o Insulin
o Growth Hormone
Target Cells and Receptors
o Target cells receive hormone
(it binds to the cell membrane
and enters the cell after it is
recognized) and initiate a
specific response.
FYI… Activity Information
Endocrine action: the hormone is distributed in
blood and binds to distant target cells.
 Paracrine action: the hormone acts locally by
diffusing from its source to target cells in the
neighborhood.
 Autocrine action: the hormone acts on the same
cell that produced it.

Endocrine Versus Nervous
o Enable cells to communicate with others
by using chemical messengers.
o Endocrine system is slower than the
nervous system because hormones must
travel through the circulatory system to
reach their target.
13
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Nerve impulse
Neuron
transmits
nerve
impulse
Neurotransmitter
released into
synapse
Postsynaptic
cell responds
(a)
Glandular
cells secrete
hormone into
bloodstream
Bloodstream
Target cells
(cells with hormone
receptors) respond
to hormone
Hormones have no
effect on other cells
(b)
14
15
MAJOR HORMONES
Pituitary Gland
Often called the
“master gland”
 Controlled by the
hypothalamus in
the brain
 Base of brain
 Anterior and
posterior pituitary
lobes

Anterior Pituitary Hormone
Growth hormone (GH)- stimulates growth
in childhood and is important for
maintaining a healthy body composition
 Problems with GH can result in too little
growth or too much growth

Dwarfism
The Alton Giant
Thyroid Gland
•
The thyroid hormones
control your metabolism
◦ Thyroxin (T4) & Triiodothyronine (T3) both increase the rate at
which cells release energy
from carbohydrates
◦ Calcitonin – regulates
calcium in blood
Parathyroid Gland

Four tiny glands that
help maintain
calcium and
phosphate levels
◦ Parathyroid
Hormone (PTH) takes calcium from
the bones to make it
available in the blood
Adrenal Gland
Each adrenal gland is
actually an organ
located right on top
of each kidney
 Outer portion called
adrenal cortex
 Inner portion called
adrenal medulla

Adrenal Cortex
Aldosterone – a mineralcorticoid, helps
kidneys conserve sodium and excrete
potassium, maintaining blood pressure
 Cortisol – glucocortoid, keeps blood
glucose levels stable
 Adrenal Sex Hormones - androgens
(male) and estrogens (female)

Pancreas


Large gland behind your
stomach that helps the
body to maintain healthy
blood sugar (glucose)
levels
Contains islands of cells
called the Islets of
Langerhans, which
secrete glucagon and
insulin
Pancreas
Insulin- secreted
when the blood
sugar level is high
 Glucogensecreted when the
blood sugar level
is low
 Both work
together to keep
blood sugar levels
balanced

Pineal Gland
located between the
cerebral hemispheres
 secretes melatoninimportant for
maintaining Circadian
rhythms (light and dark
activity)

Thymus Gland
•
•
large in young children, gradually shrinks
with age
secretes thymosins- important to
immune function
Reproductive Gland
Ovaries- estrogen progesterone
 Testes- testosterone

How Do We Maintain
Homeostasis?
We maintain it with FEEDBACK LOOPS
 We have receptors throughout our
bodies; when levels are out of
homeostasis; feedback loops are activated.
 Mostly NEGATIVE FEEDBACK loops

There are 2 Types of Feedback:
Negative and Positive
Negative Feedback - is called negative
due to the fact that you are doing the
OPPOSITE process.
For example, if you body temperature is
too high..negative feedback causes the
temperature to DECREASE .
Positive Feedback is a cascade and there is
an increase in effect.
Negative Feedback
Mechanisms
The net effect of the response to
the stimulus is the SHUT OFF
the original stimulus OR reduce
its intensity.
Why This is Negative Feedback

Beta Cells of Pancreas
Release insulin in
response to high sugar

Ultimately the
INSULIN is turned
off when sugar level
returns to normal
Positive Feedback
The initial stimulus does NOT cause a
switch to be “shut off”. Rather, a
CASCADE of more ON switches in
response to the initial response occurs.
Examples: Giving Birth and Blood Clotting
Positive Feedback: BIRTH
1.
2.
3.
4.
5.
6.
Cervix Dilates ( Initial STIMULUS)
Stimulates stretch receptors in cervix
These receptors stimulate Hypothamus (gland
in brain)
Hypothamus “tells” posterior pituitary to
release oxytocin.
Oxytocin acts on uterine muscles causing
them to contract.
Muscle contractions force baby through
cervix, stretching it. (REINFORCES
ORIGINAL STIMULUS)
Homeostatic Control Mechanisms
Negative feedback summary:
• Prevents sudden, severe changes in
the body
• Reduces the actions of the effectors
• Corrects the set point
• Causes opposite of bodily disruption to
occur, i.e. the ‘negative’
• Limits chaos in the body by creating
stability
• Most common type of feedback loop
• Examples: body temperature, blood
pressure & glucose regulation
36
Homeostatic Control Mechanisms
Positive feedback summary:
• Increases (accelerates) the actions of
the body
• Produces more instability in the body
• Produces more chaos in the body
• There are only a few types necessary for
our survival
• Positive feedback mechanisms are
short-lived
• Controls only infrequent events that do
not require continuous adjustments
• Considered to be the uncommon loop
• Examples: blood clotting and child birth
37