Physiological Psychology – Module 3
Genetic Influences – Module 5
General Psych 2
Februaty 3, 2004
Class #3
Biological Roots of Behavior
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Franz Gall (1758-1828) – Austrian
physicist who invented phrenology
He felt that bumps on the skull could
reveal our mental abilities and character
traits
Introduced as being scientific but its use
was exploited by quacks on gullible
individuals
Phrenology
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Became similar to that of astrology, palmreading and tarot
Although, ill-fated theory was laughed at
by scientific community of that day – it
may have had some validity
Localization of brain functions somehow
hit the mark
The Nervous System
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Electrochemical communication system that
enables us to think, feel, and behave
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Complex beyond comprehension
Although, human brains are more complex our
nervous systems and those of animals operate in
a similar fashion
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Allows researchers to study simple animals such as
squids and sea slugs to help us better understand the
organization of our own brains
Advantage of this is experimentation
Divisions of the Nervous
System
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Consists of two systems
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Central Nervous System (CNS) (brain and
spinal cord)
Peripheral Nervous System (PNS) which
connects the CNS to the rest of the body
Organization of the Nervous System
Peripheral Nervous System
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Two components:
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Somatic Nervous System
 Transmits sensory input to the CNS from
the outside world and directs motor output
Autonomic Nervous System
 Controls glands and muscles of our internal
organs
 “automatic pilot”
Autonomic Nervous System
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Dual system:
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Sympathetic Nervous System
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Arouses the body
Parasympathetic Nervous System
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Calms us down
Neurons
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Nerve cells (building blocks)
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Ours are essentially identical to animals
Small samples of brain tissue from a person
and a monkey are basically indistinguishable
Neural Communication
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How does a neuron communicate with other cells to
influence our behavior?
In a complicated process a neuron fires an impulse when
it receives signals from sense receptors…
The impulse is called the action potential which is a brief
electrical charge that travels down the axon which pass
messages away from the cell body to other neurons,
muscles, or glands
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Neurons are like batteries in that they generate electricity from
chemical events
This process involves the exchange of electrically charged atoms
called ions
Neural Communication
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When the action potential reaches the terminals
at an axon’s end, it triggers the release of
chemical messengers (neurotransmitters) some
of which are then sent to different parts of the
brain while others are reabsorbed by the
sending neuron in a process called reuptake
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See pages 46-49 in the text for a more detailed
description of this process
Neurotransmitters
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Neurotransmitters are chemicals made by
neurons and used by them to transmit signals to
the other neurons
A chemical message telling the next cell to fire
or not to fire its own action potential
More than 200 in our body all with different
functions
Lets briefly discuss some of the most important
ones…
Serotonin
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Facilitates a relaxed, sleepy feeling
Tryptophan which is an amino acid found
in dairy products and turkey is converted
into serotonin in the body
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So, insomnia sufferers may be smart to listen
to grandmother’s suggestion to drink a warm
glass of milk before going to bed
Some Illnesses Associated With Serotonin
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Too low levels in depression and anxiety
sufferers
Obesity may also be associated with low
levels
Linked to aggression as well -- low levels
in the brains of suicide victims
Dopamine
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High levels lead to pleasure
 Makes person feel happy and active
Dopamine raises the body's temperature and
increases metabolic rate
Gives you euphoric feelings and allows you to
be active
Drug and alcohol abuse will block dopamine
receptors and therefore a person needs to take
more to get the same effect
Illnesses Associated With Dopamine
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Parkinson’s Disease – too low levels
Schizophrenia – too high levels
Tourette’s disorder – too high levels
Huntington’s disease – too high levels
Norepinephrine
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Plays a role in attention and arousal
Used by sympathetic nervous system to
prepare us for action
Illnesses Associated With
Norepinephrine
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Depression
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Chronic stress depletes this neurotransmitter
and can lead to depression
 Note:
 Aerobic Exercise is found to protect the
brain from this depletion – so go out and
run a mile or two if your down in the
dumps
Epinephrine
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Involved in energy and glucose
metabolism
Illnesses Associated With Epinephrine
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Depression – too low levels
Acetylcholine
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Involved in voluntary movement, learning,
memory, and sleep
Helps parasympathetic nervous system to
slow our heart rate
Illnesses Associated With
Acetylcholine
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Alzheimer’s disease – too low levels
Note:
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Unfortunately, drugs used to increase
acetylcholine to help restore normal levels
appear to have small effects on improving
memory
GABA
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Inhibits excitation and anxiety
Appears directly related to anxiety
reduction
Illnesses Associated With GABA
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Anxiety disorders – too low levels
Huntington’s Disease – too low levels
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GABA systems aren’t working and this allows
dopamine systems to run wild
Huntington's disease is a hereditary disorder
characterized by memory loss, abnormal
movement and premature death
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It affects 1 in 10,000 people, and children with an
affected parent have a 50 percent chance of developing
the disease
Epilepsy – too low levels
Glutamate
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Main excitatory neurotransmitter in the
brain
Very important in learning and memory
Illnesses Associated With Glutamate
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Alzheimer’s disease
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Strokes
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Too low levels in hippocampus
Too high levels can cause neurons to die
ALS (Lou Gehrig’s Disease)
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Causes death in neurons in the spinal cord and
brainstem
Endorphins
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Involved in pain reduction and pleasure
They enhance the release of dopamine
These natural opiates are released in
response to pain and vigorous exercise
Illnesses Associated With Endorphins
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Use of artificial opiates can cause body to
stop manufacturing its own – this can lead
to drug addiction
Endocrine System: Taking the Slow
Lane
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Unlike the speedy nervous system which
zips messages from eyes to brain to hand
in a fraction of a second, endocrine
messages use the slow lane
May take several seconds or more as
bloodstream carries a hormone from an
endocrine gland to its target tissue
Endocrine System
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Hormones are chemical messengers
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Influence all aspects of our lives – growth,
metabolism, reproduction, moods, etc.
Strives for homeostasis (balance) by
responding to stress, exertion, internal
thoughts, etc.
Module 5: Genetic influences
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What influences one’s behavior:
Nature or Nurture?
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The age-old debate:
 Is it genes or is it the environment?
Principle of Genetics
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23 chromosomes carried in the egg are
paired with 23 chromosomes brought to it
by the sperm
46 chromosomes – master plan for your
body
Each is composed of a molecule called
DNA
DNA is made up of thousands of segments
which are called genes
Principle of Genetics
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Your sex is determined by the 23rd pair – the sex
chromosomes
From your mother always an “x”
From your father, you have a 50/50 chance of
receiving an x  making you a female
From your father, you have a 50/50 chance of
receiving an xy making you a male
XX = female
XY = male
Twin Studies
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Monozygotic: identical twins (one-egg)
Dizygotic: not identical – resemble one
another as much as any brother or sister
would.
Question: Do identical twins who are
adopted by separate families act like one
another more than say two adopted
children into the same family who have no
genetic influences?
“The Jim Twins”
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Thomas Bouchard’s University of
Minnesota twin studies – extraordinary
similarities between Jim Springer and Jim
Lewis (Bouchard, 1979)
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Uncanny coincidences?
Any limitations to this study?
Bouchard (1979)
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Oskar Stohl and Jack Yulfe were raised in
environments with more obvious
differences
Adoption Studies
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Surprising finding from hundred’s of
studies: people who grow up together,
whether biologically related or not – DO
NOT much resemble one another in
personality…
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Adoptee’s more similar to biological parents
than adoptive parents
Developmental Psych’s big puzzle:
 Why are children in the same family so
different???