Chapter 3: The Biological Bases of Behavior The nervous system is the body

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Chapter 3 The Biological Bases of BehaviorThe
nervous system is the bodys communication
networkBehavior depends on rapid information
travel and processingthe nervous system is the
bodys communication network, handling
information just as the circulatory system
handles blood.
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Communication in the Nervous System

• The basic components of the nervous system are
  living cells called neurons and glia.
• Hardware
• Glia structural support and insulation
• Neurons cells that receive, integrate, and
  transmit information
• Soma cell body
• Dendrites which are feeler-like structures
  specialized to receive information
• Axon a long, thin fiber that transmits signals
  away from the soma to other neurons, or to
  muscles or glands

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Neural CommunicationInsulation and Information
Transfer

• Myelin sheath an insulating material that
  speeds up transmission (MS)
• Terminal Button end of axon secretes
  neurotransmitters
• Neurotransmitters chemical messengers
• Synapse point at which neurons interconnect
• The chemicals flow across the synapse and
  stimulate the next cell.

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Figure 3.1 Structure of the neuron
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The Neural ImpulseElectrochemical Beginnings

• Hodgkin Huxley (1952) - Alan Hodgkin and
  Andrew Huxley in the 1950s discovered the
  mechanics of neural transmission by studying
  giant squidwhich have axons that are about 100
  times larger than human axons.
• Fluids inside and outside neuron
• Electrically charged particles (ions)
• Neuron at rest negative charge on inside
  compared to outside
• -70 millivolts resting potential

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The Neural Impulse The Action Potential

• Stimulation causes cell membrane to open briefly
• Positively charged sodium ions flow in
• The Action Potential Shift in electrical charge
  travels along neuron
• All or none law Either an action potential
  occurs, or it doesnt. Once an action potential
  is initiated, it goes full force

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Figure 3.2 The neural impulse
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The Synapse Chemicals as Signal Couriers

• Synaptic cleft Neurons dont actually touch at a
  synapse, instead they are separated by a
  microscopic gap between the terminal button of
  one neuron and the cell membrane of another
  neuron
• Presynaptic neuron the neuron that is sending
  the message across the gap
• Synaptic vesicles storage sacs for the
  neurotransmitter
• Neurotransmitters
• Postsynaptic neuron
• The neurotransmitters diffuse across the space
  where they find open receptor sites on the
  postsynaptic neuron. These sites recognize and
  respond to some neurotransmitters, but not to
  others

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Figure 3.3 The synapse
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When a Neurotransmitter BindsThe Postsynaptic
Potential

• Voltage change at receptor site postsynaptic
  potential (PSP)
• Not all-or-none
• Changes the probability of the postsynaptic
  neuron firing
• Positive voltage shift excitatory PSP makes the
  neuron more likely to firedecreases the
  negativity of the inside of the neuron with
  respect to the outside
• Negative voltage shift inhibitory PSP increases
  the negativity of the inside of the neuron with
  respect to the outside, making it less likely to
  fire.

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Figure 3.4 Overview of synaptic transmission
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Signals From Postsynaptic Potentialsto Neural
Networks

• One neuron, signals from thousands of other
  neurons
• Requires integration of signals
• PSPs Each neuron must integrate the many signals
  arriving at the same time before it decides to
  fire
• EPSPs pos. volt charge
• enough can cause the cells voltage to reach the
  threshold at which the action potential will
  begin
• IPSPs neg. volt shift that decrease action pot.
• EPSPs and IPSPs may balance out, as well, and the
  neuron would remain at rest
• the state of the neuron is a weighted balance

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Signals From Postsynaptic Potentialsto Neural
Networks

• Neural networks
• Thought occurs through the firing of millions of
  neurons in unison.
• Our perceptions, thoughts, and actions depend on
  patterns of neural activity in interconnected
  neurons that fire together or sequentially
• neural networks Interconnected neurons that fire
  together or sequentially

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Signals From Postsynaptic Potentialsto Neural
Networks

• Synaptic connections
• Synaptic pruning the elimination of old or
  unused synapses
• plays a larger role than the creation of new
  synapses in the sculpting of neural networks
• the number of synapses in the human visual cortex
  begins to decline after the age of 1 year.

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Figure 3.5 Synaptic pruning
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Neurotransmitters

• Specific neurotransmitters work at specific
  synapses
• Lock and key mechanism
• Agonist mimics neurotransmitter action
• Antagonist opposes action of a neurotransmitter
• 15 20 neurotransmitters known at present
• Interactions between neurotransmitter circuits
• most aspects of behavior are probably regulated
  by many

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Types of Neurotransmitters

• Acetylcholine only NT b/w motor neurons and
  voluntary muscles (every move you make depends on
  ACh)
• Nicotine is an agonist
• Monoamines
• Dopamine voluntary movements and pleasure
  emotions (Parkinsons, Schiz.)
• Norepinephrine modulates mood and arousal
  (cocaine and amphet.)
• Serotonin reg. Of sleep and wakefulness,eating
  and aggression (depression/ OCD)

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Types of Neurotransmitters

• Gaba strictly inhibitory PSPs
• Regulation of anxiety and plays a key role in
  seizures and modulation of sleep
• Endorphins resemble opiate drugs and effects,
  contribute to pain relief and some perhaps
  pleasurable emotions

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Table 3.1 Common Neurotransmitters and Some of
their Functions
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Organization of the Nervous System

• Central nervous system (CNS)
• The central nervous system consists of the brain
  and spinal cord
• Afferent nerve fibers toward the CNS
• Efferent nerve fibers away from the CNS

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Figure 3.7 The central and peripheral nervous
systems
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Organization of the Nervous System

• Peripheral nervous system the peripheral nervous
  system consists of nerves that lie outside the
  brain and spinal cord.
• Somatic nervous system voluntary portion
• Autonomic nervous system (ANS)
• governs involuntary, visceral functions
• Sympathetic mobilizes the bodys resources for
  emergencies and creates the fight-or-flight
  response
• Parasympathetic activates processes that
  conserve bodily resourcesslowing heart rate,
  reducing blood pressure, etc

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Figure 3.6 Organization of the human nervous
system
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Figure 3.8 The autonomic nervous system (ANS)
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Studying the Brain Research Methods

• Electroencephalography (EEG) monitoring
  electrical activity of the brain
• Damage studies/lesioning observing consequences
  of damage to certain areas
• Electrical stimulation (ESB) stimulating a
  portion of the brain and observing effects

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Studying the Brain Research Methods

• Transcranial magnetic stimulation (TMS) enhance
  or suppress activity in a particular region of
  the brain
• Brain imaging
• computerized tomography computer enhanced X-ray
• positron emission tomography radioactively
  tagged chemicals serve as markers of blood flow
  or metabolic activity in the brain that are
  monitored by X-ray
• magnetic resonance imaging uses magnetic fields,
  radio waves, and computer enhancement to image
  brain structure

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Brain Regions and Functions

• Hindbrain vital functions
• Medulla attaches to the spinal cord controls
  circulation, breathing, muscle tone, and
  regulating reflexes
• Pons means bridge, connects brainstem and
  cerebellum sleep and arousal
• Cerebellum means little brain coordination of
  movement and equilibrium

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Brain Regions and Functions

• Midbrain lies between the hindbrain and the
  forebrain
• integrates sensory functions
  (sight,smell,etc.)
• dopaminergic projections performance in
  voluntary movements
• reticular activating system bundle of nerve
  fibers running through the brain stem sleep and
  arousal as well as breathing and pain perception
  (hind and midbrain)
• Parkinsons disease is due to degeneration of the
  substantia nigra, a structure in the midbrain

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Brain Regions and Functions

• Forebrain emotion, complex thought
• Thalamus the way station for all incoming
  sensory information before it is passed on to
  appropriate higher brain regions
• Hypothalamus regulator of basic biological needs
  such as hunger, thirst, sex drive, and
  temperature regulation
• limbic system emotion, motivation, memory, and
  other aspects of behavior

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Brain Regions and Functions

• Forebrain (cont.)
• Cerebrum largest and most complex portion of the
  human brain, responsible for complex mental
  activities such as learning, remembering,
  thinking, and consciousness
• cerebral cortex convoluted outer layer of the
  cerebrum

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The CerebrumTwo Hemispheres, Four Lobes

• Cerebral Hemispheres two specialized halves
  connected by the
• corpus collosum thick band of fibers (axons)
  that transmits information between the
  hemispheres
• Left hemisphere verbal processing language,
  speech, reading, writing
• Right hemisphere nonverbal processing spatial,
  musical, visual recognition

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The CerebrumTwo Hemispheres, Four Lobes

• Four Lobes
• Occipital vision
• Parietal somatosensory (senses)
• Temporal - auditory
• Frontal movement, executive control systems

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Figure 3.16 Structures and areas in the human
brain
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Right Brain/Left Brain

• Brocas Area left frontal lobe plays an
  important role in the production of speech
• Wernickes Area left temporal lobe
  comprehension of speech

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Split-Brain Research

• Severing of the corpus callosum (the part that
  shares information b/w the 2 hemispheres)

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Hemispheric Specialization

• Right Hemisphere better at visual-spatial tasks,
  music, perception of emotions, neg. emotions
  exhibited
• Left Hemisphere better at verbal stimuli (lang.,
  speech, reading, and writing), positive emotions
  exhibited

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Figure 3.18 The cerebral hemispheres and the
corpus callosum
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Figure 3.19 The cerebral cortex in humans
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Figure 3.20 The primary motor cortex
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Figure 3.21 Language processing in the brain
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The Endocrine SystemGlands and Hormones

• Hormones chemical messengers in the bloodstream
• Pulsatile release by endocrine glands
• Negative feedback system The levels of many
  hormones increase to a certain level, then
  signals are sent to the hypothalamus or other
  endocrine glands to stop secretion of that
  hormone
• Endocrine glands
• Pituitary master gland, growth hormone
• Thyroid metabolic rate
• Adrenal salt and carbohydrate metabolism
• Pancreas sugar metabolism
• Gonads sex hormones

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Genes and BehaviorThe Field of Behavioral
Genetics

• Behavioral genetics the study of the influence
  of genetic factors on behavioral traits
• Chromosomes strands of DNA carrying genetic
  information
• Human cells contain 46 chromosomes in pairs
  (sex-cells 23 single)
• Each chromosome thousands of genes, also in
  pairs
• Dominant sometimes a member of a pair has a
  louder voice, always expressing itself and
  masking the other, different, member of the pair
• Recessive gene is one that is masked when the
  paired genes are different

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Genes and BehaviorThe Field of Behavioral
Genetics

• Homozygous a person has two genes in a specific
  pair that are the same
• Heterozygous a person has two genes in a
  specific pair that are different
• Genotype/Phenotype Genotype refers to a persons
  genetic makeup (lifelong), while phenotype refers
  to the ways in which a persons genotype is
  manifested in observable characteristics
  (variable)
• Polygenic Inheritance most human traits are not
  so simple with regard to genetic
  transmissionthey are polygenic, or influenced by
  more than one pair of genes.

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Figure 3.25 Genetic material
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Research Methods in Behavioral Genetics

• Family studies Family studies simply assess
  hereditary influence by examining blood relatives
  to see how much they resemble one another on a
  specific trait
• Twin studies compare resemblance of identical
  (monozygotic) and fraternal (dizygotic) twins on
  a trait (monozygotic are more correlated in terms
  of intelligence and personality, but nor
  perfectly alike- environment plays a part)

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Research Methods in Behavioral Genetics

• Adoption studies examine resemblance between
  adopted children and their biological and
  adoptive parents
• They have found very similar correlations between
  both adoptive (.20) and natural parents (.22)

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Section Summary

• Genes confer dispositions, not destinies.

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Figure 3.27 Genetic relatedness
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Figure 3.28 Family studies of risk for
schizophrenic disorders
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Figure 3.30 Twin studies of intelligence and
personality
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Modern Approaches to theNature vs. Nurture Debate

• Molecular Genetics the study of the biochemical
  bases of genetic inheritance
• Genetic mapping locating specific genes and
  their chemical sequence of specific genes on
  specific chromosomes
• The Human Genome Project produced a working
  draft of all 3 billion letters of DNA in the
  human genome (a genetic atlas)

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Modern Approaches to theNature vs. Nurture Debate

• Behavioral Genetics
• The interactionist model
• Genetic research has yielded no easy answers
  about nature vs. nurture
• Instead, it has led to the interactionist model-
  people with certain genes are more likely to
  exhibit certain behaviors when environmental
  influences are present
• Richard Rose (1995) Genes confer dispositions
  (we inherit dispositions), not destinies.

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Evolutionary PsychologyBehavior in Terms of
Adaptive Significance

• The field of evolutionary psychology is a major
  new field in psychology focusing on analyzing
  human behavior in terms of adaptive significance

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Evolutionary PsychologyBehavior in Terms of
Adaptive Significance

• Based on Darwins ideas of
• Natural selection
• Successful transmission of genetic evolution
  depends on providing either a reproductive
  advantage (fireflys light) or a survival
  advantage (turtle shell)
• Change is very gradual

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Evolutionary PsychologyBehavior in Terms of
Adaptive Significance

• Inclusive fitness
• Used to explain self-sacrifice
• An organism may succeed in helping natural
  selection by sacrificing itself to save others
  that share the same genes

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Evolutionary PsychologyBehavior in Terms of
Adaptive Significance

• Adaptations (inherited characteristics)
  behavioral as well as physical more difficult to
  study behaviors b/c they are infrequent and
  relatively quick in length of display
• Fight-or-flight response helpful in primitive
  times, but now it is related to a number of
  stress-related diseases
• Taste preferences humans show a taste preference
  for fatty foodsthis was adaptive in a
  hunter/gatherer society, when dietary fat was
  scarce

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Evolutionary PsychologyBehavior in Terms of
Adaptive Significance

• Adaptations (cont.)
• Parental investment and mating (Trivers- 1972)
• When parental investment is high for females and
  low for males, polygyny results each male seeks
  to mate with multiple females and each female
  seeks only one male.
• Polyandry female seeks to mate with multiple
  males and each male with only one female this
  emerges when parental investment is high for
  males and low for females.
• Monogamy emerges when male and female parental
  investment is roughly equal.

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• Shut-Up you!