Download What Is the Genetic Basis of Psychological Science?

Psychological Science, 3rd Edition
Michael Gazzaniga
Todd Heatherton
Diane Halpern
Biological
Foundations
3
Questions to Consider:
What Is the Genetic Basis of Psychological
Science?
How Does the Nervous System Operate?
What Are the Basic Brain Structures and Their
Functions?
How Are Neural Messages Integrated into
Communication Systems?
How Does the Brain Change?
What Is the Genetic Basis of
Psychological Science?
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Heredity Involves Passing Along Genes
through Reproduction
Genotypic Variation Is Created by Sexual
Reproduction
Genes Affect Behavior
Social and Environmental Contexts Influence
Genetic Expression
Genetic Expression Can Be Modified
Critical Thinking Skill: Seeking Disconfirming
Evidence
Learning Objective
Explain how genes transmit
information between
generations in ways that
can affect behaviors and
emotions.
What Is the Genetic Basis of
Psychological Science?
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Genetics = Inheritance and Gene Expression
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Chromosomes are made of genes
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Genes are segments of DNA
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Genes provide instructions for making proteins
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Status of “The Human Genome Project”
Each cell in the human body includes pairs of chromosomes, which consist of DNA strands. DNA
has a double helix shape and is composed of genes. The 23rd chromosome pair determines sex: A
female has two X chromosomes in that pair, whereas a male has one X and one Y.
Heredity Involves Passing Along
Genes through Reproduction
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Genes’ variations are either dominant or
recessive
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The genome represents the genotype, and
the observable characteristics are the
phenotype
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Many characteristics are polygenic
Mendel’s experiments with cross-breeding pea blossoms resulted in purple
flowers 75 percent of the time and white flowers 25 percent of the time.
Genotypic Variation Is Created
by Sexual Reproduction
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Half of each chromosome comes from each
parent and the two halves are joined
randomly
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There is enormous potential variation in the
resulting zygote’s genome
Mutations also give rise to variations
Genes Affect Behavior
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Behavioral genetics methods
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Twin studies, research on adoptees, and other
investigations of hereditary and genetic influence
provide insight into heritability
Heritability
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Behavioral geneticists can quantify the similarity
and variation in a population’s shared
characteristics
A )Fraternal twins, such as this pair pictured during their 13th birthday party, result
when two separate eggs are fertilized at the same time.
b) Identical twins result when one fertilized egg splits in two. Identical twins Gerald Levey and Mark
Newman, participants in Dr. Bouchard’s study, were separated at birth. Reunited at age 31, they
discovered they were both firefighters and had similar personality traits.
Social and Environmental Contexts
Influence Genetic Expression
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Genes guide development of characteristics
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Final expression of genes is a complex
interaction between genetic makeup and
environmental context
Genetic Expression Can Be
Modified
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Genetic manipulation has been achieved in
mammals such as mice
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Difficult in humans
Animal studies using the technique of
“knocking out” genes to determine their
effects on behaviors and on disease are a
valuable tool for understanding genetic
influences
Critical Thinking Skill
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Seeking disconfirming evidence
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We focus on information that confirms what we
already believe
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Creating a table comparing evidence from both
sides can prevent us from ignoring disconfirming
evidence
How Does the Nervous System
Operate?
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Neurons Are Specialized for Communication
Action Potentials Cause Neural
Communication
Neurotransmitters Bind to Receptors across
the Synapse
Neurotransmitters Influence Mind and
Behavior
Learning Objectives
Describe the electrical and chemical
bases for communication among
neurons.
List the major neurotransmitters and
what they do.
Neurons Are Specialized for
Communication
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Neurons are the basic building blocks of the
nervous system
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They receive and send chemical messages
All neurons have the same structure, but
neurons vary by function and by location in
the nervous system
Neurons Are Specialized for
Communication
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Types of neurons
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Sensory neurons
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Motor neurons
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Interneurons
Receptors send afferent signals to the brain for processing. An efferent signal is then
sent from the brain to the body via the spinal cord to produce a response.
Messages are received by the dendrites, processed in the cell body, transmitted along the axon,
and sent to other neurons via chemical substances released from the terminal buttons across the
synapse.
Neurons Are Specialized for
Communication
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Resting membrane potential
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When a neuron is resting, the inside and outside
differ electrically
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Sodium and potassium ions contribute to a neuron’s
resting membrane potential
A neuron at rest is polarized—it has a different electrical charge inside and outside. The passage
of negative and positive ions inside and outside the membrane is regulated by ion channels
located at the nodes of Ranvier.
Action Potentials Cause
Neural Communication
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Changes in a neuron’s electrical charge
result in an action potential, or neural firing
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Signals are excitatory or inhibitory
The electrical charge inside the neuron starts out slightly negative (resting membrane potential). As
the neuron fires, it allows more positive ions inside the cell (depolarization). Through natural
restoration (repolarization), it then returns to its slightly negative resting state.
Action Potentials Cause
Neural Communication
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Firing is the means of communication within
networks of neurons
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The all-or-none principle
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Neuron fires with the same potency every time
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How often it fires depends on the strength of
stimulation
Neurotransmitters Bind to
Receptors across the Synapse
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Neurons do not touch
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They release chemicals (neurotransmitters) into
the synapse, a small gap between the neurons
Neurotransmitters bind with the receptors of
postsynaptic neurons, thus changing the
charge in those neurons
Neurotransmitters Bind to
Receptors across the Synapse
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Reuptake
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Neurotransmitters’ effects are halted by reuptake
of the neurotransmitters into the presynaptic
neurons
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The cycle of reuptake and release repeats
continuously
Neurotransmitters Influence
Mind and Behavior
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More than 60 neurotransmitters that influence
aspects of the mind and of behavior in
humans have been identified
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Including emotions, motor skills, sleep, learning
and memory, pain control, and pain perception
Neurotransmitters Influence
Mind and Behavior
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Drugs and toxins can alter neurotransmitters
actions in several ways
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Drugs that enhance neurotransmitters’ action are
agonists
Drugs that inhibit these actions are antagonists
In this way, these substances can influence
how we think and feel
What Are the Basic Brain
Structures and Their Functions?
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The Brainstem Houses the Basic Programs
of Survival
The Cerebellum Is Essential for Movement
Subcortical Structures Control Emotions and
Basic Drives
The Cerebral Cortex Underlies Complex
Mental Activity
Learning Objectives
Identify the basic structures in
the brain and their primary
functions.
What Are the Basic Brain
Structures and Their Functions?
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The nervous system’s different parts all have
essential roles
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The central nervous system (CNS)
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Spinal cord and the brain
The peripheral nervous system (PNS)
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All the other nerve cells in the body
What Are the Basic Brain
Structures and Their Functions?
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Psychological scientists have learned a great
deal about the different brain regions through
studying people with damaged brains
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Phineas Gage
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Franz Gall and his Phrenology
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Broca’s area
Lesion in anterior association area:
Changes in personality, unable to
manage the life (homeless drifter),
deficits in long-term planning and
judgment.
This illustration shows the location of Broca’s area.
The Brainstem Houses the
Basic Programs of Survival
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At the base of the skull, the top of the spinal
cord forms the brainstem, which is involved in
basic functions such as breathing and
walking as well as general arousal
The Cerebellum Is Essential
for Movement
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The cerebellum (“little brain”), the bulging
structure connected to the back of the
brainstem, controls balance and is essential
for movement
Subcortical Structures Control
Emotions and Basic Drives
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The subcortical structures play a key part in
psychological functions
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Hypothalamus
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Controls vital functions
Thalamus
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Sensory relay
Subcortical Structures Control
Emotions and Basic Drives
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Hippocampus
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Amygdala
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Memories
Emotions
Basal ganglia
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Planning and producing of movement
The Cerebral Cortex Underlies
Complex Mental Activity
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The lobes of the cortex each play specific
roles
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Occipital
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Vision
Parietal
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Touch
The Cerebral Cortex Underlies
Complex Mental Activity
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Temporal
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hearing and speech comprehension
Frontal
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Planning and movement
The cortical representation of the body surface is organized in strips that run down the side of the
brain. Connected areas of the body tend to be represented next to each other in the cortex, and
more sensitive skin regions have more cortical area devoted to them.
This drawing, made by a hemineglect patient, omits much of the flower’s left
side.
How Are Neural Messages Integrated
into Communication Systems?
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The Peripheral Nervous System Includes the
Somatic and Autonomic Systems
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The Endocrine System Communicates
through Hormones
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Actions of the Nervous System and
Endocrine System Are Coordinated
Learning Objectives
Describe the key structures in
the endocrine system and
how they communicate to
affect behavior.
The PNS Includes the Somatic
and Autonomic Systems
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Autonomic system
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The structures and functions that regulate the
body’s internal environment
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Divided into the alarm response (sympathetic) and the
return-to-normal response (parasympathetic)
Somatic system
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Relays sensory information
The Endocrine System
Communicates through Hormones
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Both endocrine glands and organs produce
and release chemical substances
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Travel to body tissues through the bloodstream
and influence a variety of processes, including
sexual behavior
Actions of the Nervous System and
Endocrine System Are Coordinated
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The endocrine system is controlled by the
central nervous system
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Most of the central control of the endocrine
system occurs through the actions of both the
hypothalamus and the pituitary gland
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Pituitary gland controls the release of hormones
from the rest of the endocrine glands
How Does the Brain Change?
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The Interplay of Genes and Environment
Wires the Brain
Culture Affects the Brain
The Brain Rewires Itself throughout Life
Critical Thinking Skill: Recognizing Unstated
Assumptions
Females’ and Males’ Brains Are Similar and
Different
The Brain Can Recover from Injury
Learning Objectives
Explain how culture and other
environmental factors change the
brain.
Describe the similarities and differences
in females’ and males’ brains and
explain the limitations on what we can
infer from sex differences in the brain.
The Interplay of Genes and
Environment Wires the Brain
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Chemical signals influence the growth and
function of cells
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Environmental experiences, especially during
critical periods, are necessary for cells to
develop properly and for them to make more
detailed connections
Culture Affects the Brain
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Daily social interactions, which vary among
cultures (and subcultures and individuals),
are reflected each in brain’s unique
organization
The Brain Rewires Itself
throughout Life
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Although plasticity decreases with age, the
brain retains the ability to rewire itself
throughout life
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This ability is learning’s biological basis
The Brain Rewires Itself
throughout Life
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Change in the strength of connections
between neurons underlies learning
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Fire together, wire together
The functions of portions of the cerebral
cortex shift in response to activity
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Phantom limb
The participant felt a cotton swab touching his cheek as touching his missing hand. This
effect may occur because the hand and face are near each other in somatosensory
space.
The Brain Rewires Itself
throughout Life
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The puzzle of synesthesia
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Cross-sensory experience is called synesthesia
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Example: some people taste words or hear colors
Synesthesia is genetic
Critical Thinking Skill
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Recognizing unstated assumptions
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All human interactions are based partly on
assumptions
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When trying to understand a complex topic,
recognize unstated assumptions so that you can
apply reason to them
Females’ and Males’ Brains
Are Similar and Different
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Sex differences in the brain reflect biological
and environmental effects
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Males’ and females’ brains are predominantly
similar
Females’ and Males’ Brains
Are Similar and Different
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Differences in males’ and females’ brains:
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Males’ brains are larger than females’ (on average)
Females’ verbal abilities are organized more
bilaterally (more equally in both hemispheres)
Females’ brains have a greater proportion of gray
matter, while males’ brains have a greater
proportion of white matter
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Females’ and Males’ Brains
Are Similar and Different
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There is no basis for deciding that either sex
has the “better” brain
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The sexes’ differences in information processing
arise from environmental experiences and genetic
propensities
A considerable body of evidence indicates that female brains are more bilaterally organized for language. For
example, researchers at Indiana University studied men and women listening to someone reading aloud. As these
fMRI images show, the men listened with one side of their brains, whereas the women tended to listen with both
sides.
The Brain Can Recover from
Injury
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The brain can reorganize its functions in
response to brain damage
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This capacity decreases with age
Transplanted stem cells may be able to grow
to replace damaged neurons
The Brain Can Recover from
Injury
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Anomalies in sensation and in perception,
such as synesthesia, are attributed to crosswiring connections in the brain