Biological Bases of
Behavior
Part Four – The Endocrine System
The Endocrine System
• Neurons and neural communication aren’t the
only way information is communicated by our
bodies. Sometimes, an alternate system
communication called the endocrine system,
is used.
• The endocrine system operates by use of
specialized groups of cells called glands,
which secrete chemicals, called hormones.
Biological Basis 4
The Endocrine System
• While the neural communication is fast, to
allow us to react quickly to environmental
stimuli, the endocrine system is slower and
represents more long-term information
transfer.
Biological Basis 4
Hormones and Glands
• Hormones foster growth and proliferation of
cells, as well as growth and development of
the body in general.
• Hormones perform their work by interacting
with receptors on the surface of target cells,
or by entering the cells and interacting with
specialized molecules inside them.
Biological Basis 4
Hormones and Glands
• Hormones are similar to neurotransmitters in
that they are chemicals which interact with
receptors on one cell after being secreted by
another, and like neurotransmitters,
hormones are key aspects of internal
communication; some acting as
neurotransmitters when secreted by neurons.
• Hormonal control is largely an unconscious
process, by which the body monitors the
levels of the given hormone and the activities
it affects through a negative feedback loop.
Biological Basis 4
The Adrenal System
• The adrenal glands
are located above
the kidneys in two
parts. The first is
the adrenal medulla
and the second is
the adrenal cortex.
The adrenal glands
are important for
our energy levels,
moods, and stress
reactions.
Biological Basis 4
The Adrenal System
• The medulla secretes two hormones:
epinephrine and norepinephrine. These two
chemicals are also neurotransmitters in the
nervous system, and they are important for
arousal and the fight-or-flight response of the
autonomic nervous system.
Biological Basis 4
The Adrenal System
• The adrenal cortex produces more than 50
hormones for various functions vital for a
physiological survival and reproductive
function.
• Anabolic steroids, synthetic forms of male sex
hormones produced by the adrenal cortex
can cause hyperaggression, mood swings,
and mental instability if taken in high doses.
Biological Basis 4
3
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• The Endocrine System
Pituitary Gland
Thyroid Gland
Adrenal Glands
Pancreas
Ovaries/Testes
Biological Basis 4
– Endocrine Glands
The Thyroid and Pituitary
Glands
• The thyroid gland
regulates the
metabolic rate of
cells by producing
the hormone
thyroxine.
Biological Basis 4
The Thyroid and Pituitary
Glands
• Overproduction of this hormone can lead to
hyperthyroidism, which is characterized by
weight loss, high blood pressure, and
muscular weakness.
• Too little causes hypothyroidism, associated
with slow metabolism, weight gain, and
sluggishness
Biological Basis 4
3
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•
•
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• The Endocrine System
Pituitary Gland
Thyroid Gland
Adrenal Glands
Pancreas
Ovaries/Testes
Biological Basis 4
– Endocrine Glands
The Thyroid and Pituitary
Glands
• The pituitary gland
is sometimes called
the master gland
because many
endocrine glands
release hormones in
response to
hormones released
by the pituitary.
Biological Basis 4
The Thyroid and Pituitary
Glands
• The pituitary, is in turn, controlled by the
hypothalamus (in the forebrain) to which it is
attached.
Biological Basis 4
The Thyroid and Pituitary
Glands
• The pituitary acts as a bridge between the
endocrine system and the nervous system;
the nervous system signals a stressful
situation to the brain, and the brain
stimulates the pituitary to release
adrenocorticotropic hormone (ACTH), our
primary stress hormone, to affect other
organs, such as the adrenal glands.
Biological Basis 4
3
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• The Endocrine System
Pituitary Gland
Thyroid Gland
Adrenal Glands
Pancreas
Ovaries/Testes
Biological Basis 4
– Endocrine Glands
3
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•
•
• The Endocrine System
Pituitary Gland
Thyroid Gland
Adrenal Glands
Pancreas
Ovaries/Testes
Biological Basis 4
– Endocrine Glands
3
•
•
•
•
•
• The Endocrine System
Pituitary Gland
Thyroid Gland
Adrenal Glands
Pancreas
Ovaries/Testes
Biological Basis 4
– Endocrine Glands