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


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

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

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

Figure 3.1 Structure of the neuron
The Neural Impulse Electrochemical 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

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

Figure 3.2 The neural impulse
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
  • Presynaptic neuron the neuron that is sending
    the message across the gap
  • Synaptic vesicles storage sacs for the
  • 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

Figure 3.3 The synapse
When a Neurotransmitter Binds The Postsynaptic
  • 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

Figure 3.4 Overview of synaptic transmission
Signals From Postsynaptic Potentials to Neural
  • One neuron, signals from thousands of other
  • Requires integration of signals
  • PSPs Each neuron must integrate the many signals
    arriving at the same time before it decides to
  • EPSPs pos. volt charge
  • enough can cause the cells voltage to reach the
    threshold at which the action potential will
  • 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

Signals From Postsynaptic Potentials to Neural
  • 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

Signals From Postsynaptic Potentials to Neural
  • 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.

Figure 3.5 Synaptic pruning
  • Specific neurotransmitters work at specific
  • 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

Types of Neurotransmitters
  • Acetylcholine only NT b/w motor neurons and
    voluntary muscles (every move you make depends on
  • 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)

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

Table 3.1 Common Neurotransmitters and Some of
their Functions
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

Figure 3.7 The central and peripheral nervous
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
  • Parasympathetic activates processes that
    conserve bodily resourcesslowing heart rate,
    reducing blood pressure, etc

Figure 3.6 Organization of the human nervous
Figure 3.8 The autonomic nervous system (ANS)
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

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

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

Brain Regions and Functions
  • Midbrain lies between the hindbrain and the
  • integrates sensory functions
  • 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

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

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

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

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

Figure 3.16 Structures and areas in the human
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

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

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

Figure 3.18 The cerebral hemispheres and the
corpus callosum
Figure 3.19 The cerebral cortex in humans
Figure 3.20 The primary motor cortex
Figure 3.21 Language processing in the brain
The Endocrine System Glands 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
  • Endocrine glands
  • Pituitary master gland, growth hormone
  • Thyroid metabolic rate
  • Adrenal salt and carbohydrate metabolism
  • Pancreas sugar metabolism
  • Gonads sex hormones

Genes and Behavior The Field of Behavioral
  • Behavioral genetics the study of the influence
    of genetic factors on behavioral traits
  • Chromosomes strands of DNA carrying genetic
  • Human cells contain 46 chromosomes in pairs
    (sex-cells 23 single)
  • Each chromosome thousands of genes, also in
  • 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

Genes and Behavior The Field of Behavioral
  • 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
  • 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.

Figure 3.25 Genetic material
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)

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)

Section Summary
  • Genes confer dispositions, not destinies.

Figure 3.27 Genetic relatedness
Figure 3.28 Family studies of risk for
schizophrenic disorders
Figure 3.30 Twin studies of intelligence and
Modern Approaches to the Nature 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)

Modern Approaches to the Nature 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.

Evolutionary Psychology Behavior 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

Evolutionary Psychology Behavior 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

Evolutionary Psychology Behavior 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

Evolutionary Psychology Behavior 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

Evolutionary Psychology Behavior 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.

  • Shut-Up you!