Download The Endocrine System

The Endocrine System
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
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How are the endocrine and nervous
systems similar?
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The Endocrine System and the Nervous
System are two communication systems for
sending information to and from the brain
They operate differently of course
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Introduction
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The endocrine system includes the organs of the body that
secrete hormones directly into body fluids such as blood
Regulates chemical reaction in cells and therefore control
functions of the organs, tissues, and other cells
bloodstream
to
Glands
into
secrete
hormones
target tissues
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What are hormones?
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Chemicals secreted by a cell that affect the functions of other
cells
How do they affect behavior?
Hormones affect the growth of bodily structures (muscles
and bones), affecting what you can do physically
They affect metabolic processes, influencing the amount of
energy you have
Certain hormones cause the differences between boys and
girls
Other hormones prepare the body for action during stress
Hormones also act in the brain to directly influence moods
and drives
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Hormones work like neurotransmitters in that
they have a special molecular structure that
match the structure of a receptor
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Hypothalamus
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Controls the pituitary gland
It monitors the amount of hormones in the
blood
Sends out messages to correct hormonal
imbalances
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Pituitary Gland
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Controlled by the hypothalamus
Located at the base of the brain
How does the pituitary gland act as the “Master
Gland?”
It secretes a large number of hormones, many of
which control the output of hormones by other
endocrine glands – it’s the boss of other glands
Secretes the growth hormone - GH
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Thyroid Gland
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Located below the larynx (voice box)
Controls how fast your body uses energy with
controls your weight…metabolism
Secretes the hormone thyroxine which
controls the rate at which your body burns and
uses energy
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Thyroid Gland
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What happens if there’s too much or too
little thyroxine?
Hypothyroidism – too little; become tired
Hyperthyroidism – too much; overactive,
lose weight and sleep
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Extra
Parathyroid Glands
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Four located on the posterior surface of the
thyroid gland
Secrete parathyroid hormone (PTH)
It’s responsible for bone growth and for
regulating the calcium level in body
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Adrenal Glands
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Located on top of each kidney
Becomes active when angry or scared
Secretes the hormones…
Epinephrine (adrenaline)
Norepinephrine (noradrenaline)
Same effects as sympathetic nervous system
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Adrenal Glands
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epinephrine (adrenaline) increases blood pressure, breathing
rate and energy level
norepinephrine (nonadrenaline) causes the heartbeat and
breathing to increase; raises blood pressure
Both generate the extra energy needed to handle a difficult
situation
Both can heighten emotions such as fear and anxiety
Norepinephrine sends out a chemical that will clot blood faster
just in case we get cut
Glands also secrete cortical steroids – help muscles develop
and cause the liver to release stored sugar when the body
requires extra energy for emergencies
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Extra
Other Hormone-Producing Organs
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Pineal gland
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Small gland
Located between
cerebral hemispheres
Melatonin
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Regulates circadian
rhythms
May play a role in
onset of puberty
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Thymus gland
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Located between
lungs
Thymosin
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Helps with
immunity
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Pancreas
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Located behind the stomach
Both exocrine gland and
endocrine gland
Exocrine – secretes digestive
enzymes into a duct leading to
the small intestine
Endocrine – secretes hormones
into bloodstream
Regulates the metabolism of
sugar
Secretes insulin which lowers
blood sugar (used to treat Type 1
Diabetes
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The Gonads
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The Ovaries
Reproduction in females
Secrete estrogen and progesterone
Their levels vary…PMS
Responsible for female sex characteristics
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The Gonads
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Testes
Testosterone
important in physical development of male
In prenatal period, it helps decide the sex of a fetus
In adolescence, it’s important for growth of muscle and
bone along with the growth of male sex characteristics
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Hormone versus a Neurotransmitter
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When a chemical is used as a
neurotransmitter, it is released right beside
the cell that it is to excite or inhibit
When a chemical is used as a hormone, it is
released into the blood, which diffuses it
throughout the body
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© 2009 The McGraw-Hill Companies, Inc. All rights reserved