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The Body and the
Brain
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The
Nervous
System
The nervous system regulates our internal functions.
The central nervous system consists of the brain and the spinal
cord.
The peripheral nervous system is made up of nerve cells that
send messages between the central nervous system and all the
parts of the body.
Neurons - or nerve cells – run through our bodies and
communicate with each other.
Neurons send and receive messages from other structures of the
body, such as muscles and glands.
Each of us has over 100 billion neurons – mostly found in our
brains.
Neurons look like trees.
Each neuron is made up of a cell body, a dendrite, and an axon.
The cell body looks like the top of the trunk. The cell body
produces energy that fuels the activity of the cell.
The axons look like the root of a tree. They carry messages away
from the center cell body.
The dendrites look like the branches of the tree. They receive
information from other neurons and pass the message through
the cell body.
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Some neurons are as small as an inch in length.
Others, like the neurons that run through our
legs, can be several feet long.
Myelin is a white fatty substance that insulates
and protects the axon.
The myelin casing also helps to speed up the
transmission of the message.
The fibers at the end of the axon are called axon
terminals.
Messages are sent from the axon terminals of
one neuron to the dendrites of other neurons.
In order for the messages to be sent to each
other, they must travel across the synapse – or
the junction between the axon terminals of one
neuron and the dendrites of another.
The coolest part about the synapse is the fact
that new ones develop between neurons when we
learn something new.
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Neurons travel in varying directions depending on
the message.
For example, when you stub your toe, the
sensory neurons carry information received by
the senses to the central nervous system.
Motor neurons are the nerve cells that carry
information from the CNS to the muscles and
glands and influence their functions.
When you touch the hot stove, the sensory
neurons tell the CNS that the stove is hot.
The motor neurons then travel from the CNS to
tell the muscle to move the hand away from the
stove.
Other motor neurons may stimulate the heart
and make it beat faster because of the situation.
A neurotransmitter is a chemical that is
stored in sacs in the axon terminals.
 There are several types of
neurotransmitters.
 When a person thinks about a friend,
waves their hand, or yawn,
neurotransmitters are involved.
 Dopamine is a neurotransmitter that is
involved primarily in motor behavior.
 A deficiency in dopamine levels
contributes to Parkinson’s Disease – which
involves a loss of muscle control filled in
with tremors and rigid movement.
 An excess of dopamine contribute to
schizophrenia.
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The Central Nervous System
The spinal cord extends from the brain
down the back, ending below the hips.
 The spinal cord is a column of nerves and
it is protected by the bones of the spine.
 The spinal cord is also responsible for
spinal reflexes.
 A spinal reflex is an automatic response to
something – like the hot stove/pull away
situation.
 Why do we blink when dust gets in our
eyes? Why do some of us sneeze when
we sniff pepper?
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The peripheral nervous system lies
outside the central nervous system.
 The somatic nervous system
transmits sensory messages to the
CNS.
 The SNS allows us to experience the
difference between hot and cold, pain
and pleasure.
 The autonomic nervous system
regulates the body’s vital functions,
such as heartbeat, breathing,
digestion, and blood pressure.
 The autonomic nervous system is
interesting because is can be effected
by emotion.
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The fight-or-flight response occurs because the
sympathetic system is activated when a person is
“going into action”.
This sympathetic system can disturb the ANS. Stress
can cause digestion to falter, can increase and
decrease the heartbeat in specific situations, and can
elevate the blood pressure.
The parasympathetic system restores peace in the
body.
ANS
THE BRAIN
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The brain is divided into three sections: the
Hindbrain, the Midbrain, and the Forebrain.
THE HINDBRAIN:
The medulla is involved in vital functions
such as heart rate, blood pressure, and
breathing.
The Pons is located in the front of the
medulla and is involved in regulating body
movement, attention, sleep, and alertness.
The cerebellum is responsible for balance
and coordination. A person with an injured
cerebellum might walk funny or fall over.
THE MIDBRAIN:
 The midbrain contains the parts of the
brain that are involved in vision and
hearing.
 The reticular activating system is
important for attention, sleep, and
arousal.
 Stimulation of this portion of the brai
makes us alert and increases brain
activity.
 Some drugs, such as alcohol, reduce the
activity of the RAS, which mean the
alertness and reaction time will decrease.
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THE FOREBRAIN:
 The forebrain contains four key areas.
 The thalamus is a relay station for sensory
stimulation.
 The thalamus transmits sensory input
such as pain or images captured by the
eyes.
 The hypothalamus (hypo – Greek prefix
meaning “under”) is located under the
thalamus.
 The hypothalamus regulates body
temperature, hunger, thirst, sexual
behavior, caring for offspring, etc.
 The hypothalamus is all about instinct, but
humans, unlike animals, use cognitive
thoughts – not just instinct.
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The limbic system is involved in learning
and memory, emotion, hunger, sex, and
aggression.
If a part of the limbic system is damaged,
people can remember old memories, but
cannot form new memories.
Damage can also lead people to act
passively or aggressively without cause.
The cerebrum (Latin for brain) makes up
70% of the weight of the brain.
The cerebral cortex is the outer layer of the
brain.
It is composed of two sides – the right and
the left. Each side is called a hemisphere.
The information transmitted from one side is
transmitted to the other side of the body.
The structure that connects the two
hemispheres is the corpus callosum.
The Two Sides
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The cerebral cortex is
composed of two sides – or
hemispheres.
Hemi – Greek for “half”
The left hemisphere controls
the right side of your body.
The right hemisphere controls
the left side of your body.
The corpus callosum aids in
getting info from one side to
the other.
For right-handed people,
language originates on the
left.
The language functions are
usually associated with math
and logic.
People who are supposedly
logical are “left-brained”.
The right brain (non-language
side) is more emotional,
creative.
“Right-Brain” types are
artistic and imaginative.
However, this “right/Leftbrain” is mostly invalid and
based on myth.
The Lobes
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Each hemisphere has four
parts, or lobes.
The frontal lobe is
sometimes called the
“executive center”
This is where we solve
problems, make decisions,
and store working
memory.
Within the frontal lobe,
Broca’s area controls facial
muscles – so when people
injure this area, they may
speak slowly and simply.
The occipital lobe contains
the primary visual area of
the cortex.
When light strikes the eye,
neurons in the occipital
lobe fire, allowing us to
see.
Damage to this lobe can
cause people to recognize
an object, but they could
be unable to differentiate
that object from a similar
object.
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Skin sensations are
felt through the
parietal lobe.
Different neurons
fire depending on
the sensation –
such as stubbing
your toe, or getting
stung by a bee.
The temporal lobe
collects sounds
picked up by the
thalamus – and we
hear sounds!
Association areas
shape information
into something
meaningful, and
each lobe has its
own association
area.
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Let’s Review
2 parts of the nervous system
– Central Nervous System
– Peripheral Nervous System
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3 sections of the brain
– Hindbrain
 Lower
portion, vital functions, balance and coordination
– Midbrain
 Vision
and hearing
– Forebrain
 Complex
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thought and emotions
4 association areas of the brain (make
meaning of information, located in the cebral
cortex)
– Frontal, parietal, occipital, temporal
The Two Sides
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The cerebral cortex is
composed of two sides – or
hemispheres.
Hemi – Greek for “half”
The left hemisphere controls
the right side of your body.
The right hemisphere controls
the left side of your body.
The corpus callosum aids in
getting info from one side to
the other.
For right-handed people,
language originates on the
left.
The language functions are
usually associated with math
and logic.
People who are supposedly
logical are “left-brained”.
The right brain (non-language
side) is more emotional,
creative.
“Right-Brain” types are
artistic and imaginative.
However, this “right/Leftbrain” is mostly invalid and
based on myth.
Right brain v. left brain
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Even though there are some characteristics that
are associated with each hemisphere, the
corpus callosum allows the hemispheres to work
together (rather than separately)
When the corpus callosum is damaged (or cut in
surgery), the communication between
hemispheres is altered, and that does effect
some functions
– If a patient holds an object in their left hand
(projected to the right hemisphere, the “nonlanguage” side, then the left brain might not be
able to communicate and say what the object is
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This situation demonstrates something called
hemispheric specialization, which means certain
functions are controlled by a certain side of the
brain (AKA brain lateralization)
Testing the Brain
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Accidents give researchers a window into the brain.
Examples, such as Phineas Gage, show psychologists and scientists
how different parts of the brain respond to damage.
In 1969, Jose Delgado experimented with electrical stimulation on the
brain.
He determined that when an implanted electrode in a bull’s brain, he
could use electrical charges to stop a bull in the middle of a charge.
Basically, his thesis stated that electrical stimulation to various parts
of the brain could change behavior.
An EEG – or electroencephalogram – is a device that records the
electrical activity of the brain.
Electrodes attached to the skull pick up on the electrical charges –
called brain waves – and patterns of these waves can be associated
with sleep, thought, and relaxation.
A CAT – or computerized axial tomography – scan determines how
dense brain tissue is by recording how much radiation is absorbed by
an X-ray.
A MRI- magnetic resonance imaging- a person lies in a powerful
magnetic field and radio wave cause the brain to give off energy- more
powerful than a CAT scan
A PET – or Positron Emission Tomography – shows brain activity as it
occurs so researchers can see which parts of the brain are stimulated
when listening to music, performing math, or having a discussion with
friends.
PET scan
CAT scan
MRI of brain on Meth
GLANDS
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The endocrine system consists of glands that
secrete substances called hormones into the
bloodstream.
Hormones stimulate growth and reactions, such as
changes in mood and activity levels.
Hormones are produced by several different glands.
The pituitary gland (just the size of a pea and
situated under the hypothalamus), controls growth
hormones, hormones (Oxytocin) that stimulate
labor for pregnant women, and “mothering
instincts”.
The thyroid gland produces thyroxin which affects
the body’s metabolism.
Too little thyroxin leads to hypothyroid disorder –
and these people can be overweight.
Too much thyroxin leads to hyperthyroid disorder,
which can make people lose weight, become
hyperactive, or sleepless.
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The adrenal glands are located above the kidneys
and secrete cortical steroids.
Cortical steroids increase resistance to stress and
promote muscle development.
The adrenal glands also release adrenaline… meant
to help people in a stressful situation.
Nonadrenaline also steps in to help calm people
during the stressful situation, whereas adrenaline
prepares people for a fight. (Fight-or-Flight
response)
The Testes produce testosterone and small amounts
or estrogen and progesterone in males.
It is responsible for pushing boys through puberty so
that they are ready to reproduce.
The ovaries produce estrogen and progesterone and
small amounts of testosterone in women.
Again, the ovaries prepare women for puberty –
which lead to reproduction and childbirth.
Really, sexual attraction is very chemical (or
hormonal) because women have higher libido’s when
they are ovulating because there is more estrogen in
their body.
Heredity
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Heredity is the transmission of characteristics from
parents to offspring.
Heredity – while determining hair color, eye color
and height – can also determine some psychological
traits.
Shyness, leadership, aggressiveness, etc., can be
linked to heredity.
However, for years, the debate has raged on about
Nature vs. Nurture.
Does heredity really determine behavior?
Or is it purely based on upbringing?
As humans, we loath the nature idea because it
states that everything is predetermined – meaning
that we cannot become smarter or more athletic than
our biology allows.
Psychologists argue that heredity cannot determine
destiny because the environment DOES determine
how a person develops.
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The best way to test this debate is by studying….?
Twins.
Identical twins share 100% of their genes.
Their DNA is identical, yet their fingerprints are
different…
Fraternal twins, however, only share about 50% of
their genes.
Therefore, identical twins are more likely to share
traits – both positive and negative.
Identical twins, for example, are more likely to both
develop autism than fraternal twins.
Beginning in 1979, Thomas Bouchard began studying
twins that were being reared apart.
He found that twins who had never met one another
– and had been “nurtured” differently – still shared
unique mannerisms.
Researchers also study adopted children because
they are removed from their biological families and
can still share commonalities with their actual
parents.
These studies can be controversial because it relies
on twins, siblings, or children to remain apart –
which is difficult to maintain ethically at times.