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Chapter Two
Biological
Foundations of
Behavior
Did You Know That…
• Some cells in your nervous system are
more than three feet long?
• Our bodies produce natural painkillers that
are chemically similar to morphine and
other narcotic drugs?
• Fetuses not only suck their thumbs in the
womb, but that 95% of them suck their
right thumbs?
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Did You Know That… (Cont’d)
• Though a man survived an accident in
which a thick metal rod was driven right
through his skull, his personality changed
so much that people thought he was no
longer himself?
• Men’s and women’s bodies produce both
male and female sex hormones?
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Did You Know That… (Cont’d)
• Scientists have deciphered the entire
human genetic code and posted it on the
Internet?
• Raising the body temperature of a finger
may relieve the pain of a migraine
headache?
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Module 2.1
Neurons: The Body’s Wiring
Module 2.1 Preview Questions
• What is a neuron?
• What are the parts of a neuron?
• What are the types of neurons and types
of cells found in the nervous system?
• How is a neural impulse generated and
transmitted from one neuron to another?
• What roles do neurotransmitters play in
psychological functioning?
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Figure 2.1: The Neuron
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Cells in the Nervous System
• Three types of neurons
• Sensory neurons (or “afferent neurons”)
• Motor neurons (or “efferent neurons”)
• Interneurons (or “associative neurons”)
• Glial cells
• Account for 90% of cells in adult human brain
• Help hold neurons together
• Provide supports for the nervous system
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Figure 2.2: An Action Potential
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Figure 2.3: How Neurons Communicate
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Preventing the Continued Stimulation of a
Receiving Neuron
• Reuptake
• Enzymes in the synapse
• Release of neuromodulators
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Functioning of Neurotransmitters
• Normal functioning requires balance.
• Disorders may result from:
• Neurotransmitter excess
• Neurotransmitter deficit
• Irregularities in functioning
• Effects influenced by drugs or chemicals:
• Antagonists
• Agonists
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Neurotransmitter-Related Disorders
• Schizophrenia
• May be the results of irregularities in the
utilization of dopamine
• Antipsychotic drugs block receptor sites for
dopamine
• Parkinson’s disease
• Occurs from a loss of dopamine-producing
cells
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Effects of Agonists
• Caffeine increases availability of glutamate.
• Amphetamines and cocaine increase availability
of dopamine in the brain.
• Alcohol and antianxiety drugs increase the
sensitivity of receptor sites to GABA.
• Antidepressants increase levels of
norepinephrine and serotonin.
• Morphine and heroin mimic effects of naturally
occurring endorphins.
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Module 2.2
The Nervous System:
Your Body’s Information Superhighway
Module 2.2 Preview Questions
•
•
•
•
How is the nervous system organized?
What are spinal reflexes?
What is the autonomic nervous system?
What is the relationship between the
sympathetic and parasympathetic
divisions of the autonomic nervous
system?
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Figure 2.4: Parts of the Nervous System
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Concept Chart 2.2:
Organization of the Nervous System
The Nervous System
Central
Nervous System
Spinal Chord
Peripheral
Nervous System
Brain
Somatic
Nervous System
Autonomic
Nervous System
Sympathetic
Nervous System
Parasympathetic
Nervous System
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Central Nervous System
• Consists of:
• Brain
• Spinal cord
• CNS regulates everything in the body.
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Spinal Cord
• Column of nerves extending from brain
• Protected by the spine
• Transmits information between the brain and
the peripheral nervous system
• Controls some spinal reflexes
• Allows quick responses to particular types of
stimuli
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Figure 2.5a: The Knee-Jerk Reflex
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Figure 2.5b: The Withdrawal Reflex
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Peripheral Nervous System
• Connects the CNS with the other parts of
the body
• Divided into two parts:
• Somatic Nervous System: Transmits
messages between CNS and the sensory
organs, glands, and muscles
• Autonomic Nervous System: Controls internal
bodily processes
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Divisions of the Autonomic Nervous System
• Sympathetic Nervous System
• Speeds up bodily processes
• Draws energy from stored reserves
• Activation often accompanied by strong emotions
• Parasympathetic Nervous System
• Fosters bodily processes that replenish energy
stores
• Helps conserve energy by slowing down other bodily
processes
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Module 2.3
The Brain: Your Crowning Glory
Module 2.3 Preview Questions
• How is the brain organized, and what are
the functions of its various parts?
• How is the cerebral cortex organized?
• What are the major functions associated
with the four lobes of the cerebral cortex?
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Hindbrain
• Lowest, oldest part of the brain
• Includes the:
• Medulla
• Pons
• Cerebellum
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Figure 2.6: The Brainstem
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Midbrain
• Contains nerve pathways that connect the
hindbrain with the forebrain
• Midbrain structures perform important
roles
• e.g., control of automatic movements of the
eye muscles
• Reticular formation plays key role in
regulating states of attention, alertness,
and arousal.
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Major Structures of the Forebrain
• Thalamus
• Relays sensory information to appropriate
parts of the cerebral cortex
• Receives input from the basal ganglia
• Hypothalamus
• Regulates many vital bodily functions as well
as emotional states, aggressive behavior, and
response to stress
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The Limbic System
• Group of interconnected structures:
• Amygdala: Helps regulate states of emotional
arousal
• Hippocampus: Plays important role in the
formation of memories
• Parts of the thalamus
• Parts of the hypothalamus
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The Cerebral Cortex
• Thin, outer layer of the largest part of the
forebrain which is called the cerebrum
• Cerebrum consists of the right and left
cerebral hemispheres.
• Hemispheres connected by the corpus
callosum
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Figure 2.7: The Size of the Cerebral Cortex
in Humans and Other Animals
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Figure 2.8: Lobes of the Cerebral Cortex
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Table 2.1: The Lobes of the Cerebral Cortex
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Figure 2.9: Somatosensory Cortex and Motor
Cortex
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Module 2.4
Methods of Studying the Brain
Module 2.4 Preview Questions
• What recording and imaging techniques
are used to study brain functioning?
• What experimental methods do scientists
use to study brain functioning?
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Recording and Imaging Techniques
•
•
•
•
•
EEG (electroencephalograph)
CT (computed tomography) scan
PET (positron emission tomography) scan
MRI (magnetic resonance imaging)
fMRI (functional MRI)
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Experimental Methods
• Lesioning
• Electrical recording
• Electrical stimulation
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Module 2.5
The Divided Brain:
Specialization of Function
Module 2.5 Preview Questions
• What are the major differences between
the left and right hemispheres?
• What determines handedness?
• What can we learn about brain
lateralization from studies of “split-brain”
patients?
• What are the major causes of brain
damage, and what effects do they have on
psychological functioning?
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Lateralization of Brain Functions
• Refers to division of functions between
right and left hemispheres
• Left hemisphere dominant for language
abilities, logical reasoning, and problem
solving
• Right hemisphere dominant in nonverbal
processing
• People are not “left-brained” or “rightbrained.”
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Figure 2.15: Broca’s and Wernicke’s Area
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What Determines Handedness?
• Genetics factors
• Neither parent left handed: Odds are 1 in 50
• One parent left-handed: Odds are 1 in 6
• Both parents left-handed: Odds are 1 in 2
• Social factors
• Prenatal hormones
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Split-Brain Research
• Severing corpus callosum as treatment for
severe epilepsy
• Split-brain patients retain intellect and
personality
• But differences in perception, language
evident in special testing circumstances
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Figure 2.16: Split-Brain Study
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Figure 2.16: Split-Brain Study (Cont’d)
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Brain Damage and
Psychological Functioning
• Case of Phineas Gage: Prefrontal cortex
damage
• Plasticity: Ability of the brain to adapt and
reorganize itself following trauma or
surgical alteration
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Module 2.6
The Endocrine System:
The Body’s Other Communication System
Module 2.6 Preview Questions
• What are the major endocrine glands?
• What roles do hormones play in behavior?
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Endocrine System
• Another communication system in the
body
• But much slower than the nervous system
• Messages conveyed through blood
vessels using hormones
• Regulates important bodily processes
• Helps body to maintain homeostasis
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Figure 2.18: Major Glands
of the Endocrine System
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Hormones and Behavior
• Testosterone and aggression
• Thyroid hormones and metabolism
• Excess: anxiety and irritability
• Deficit: sluggishness
• Premenstrual syndrome (PMS)
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Module 2.7
Genes and Behavior:
A Case of Nature and Nurture
Module 2.7 Preview Questions
• What roles do genetic factors play in
behavior?
• What are the methods used to study
genetic influences on behavior?
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Genetic Influences on Behavior
• Nature-nurture problem
• Genotype: An organism’s genetic code
• Phenotype: The observable physical and
behavioral characteristics of the organism
• Genetic and environmental influences
interact in complex ways to shape our
personality.
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Kinship Studies
• Familial association studies
• Twin studies
• Identical (MZ) vs. fraternal (DZ) twins
• Concordance rates
• Adoptee studies
Continue
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Figure 2.19: Genetic Overlap Among Family
Members
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Figure 2.20: Familial Risk in Schizophrenia
Return
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Application: Module 2.8
Biofeedback Training:
Learning by Listening to the Body
Module 2.8 Preview Question
• What is biofeedback training?
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Biofeedback Training (BFT)
• Monitoring equipment provides information
about internal functioning such as:
•
•
•
•
Heart rate
Blood pressure
Muscle tension
Temperature
• Through feedback, gain some degree of
conscious control over physiological
functioning
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