Chapter 3 Biological Psychology

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Chapter 3Biological Psychology
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Biological Psychology

• In this chapter we will examine
• What are the components of the nervous system?
• How does the brain create mental processes and
  behavior?
• What we understand least is why brain
  activity produces experience at all. -- James
  W. Kalat

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Module 3.1

• Genes and Behavior

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Genes and Behavior

• From research we know that genetic factors have a
  substantial influence on many aspects of
  psychology. But we still dont know
• How genes shape mental processes and behavior
• How much influence genes actually have
• Which aspects of the environment are most
  important in influencing psychological processes
• How do genes and environment work together
  to shape mental processes and behavior?

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• Figure 3.2 
• Genes are sections of chromosomes in the nuclei
  of cells. (Scale is exaggerated for illustration
  purposes.)

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Genetic Principles

• Chromosomes
• Most animal and plant cells contain a nucleus
  with hereditary material instructions in the
  form of strands called chromosomes.
• Humans have 46 chromosomes 23 pairs in every
  body cell except for the sex cells. Sperm and ova
  each contain 23 unpaired chromosomes that unite
  at conception.

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Genetic Principles

• Genes
• The genes that form the sections of the
  chromosomes control the chemical reactions that
  direct an individual organisms development.
• Genes control protein production in order to
  produce specific characteristics a specific
  group of genes will exert a large influence over
  height, weight, or eye color.

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Genetic Principles

• Genes
• Genes are composed of DNA, special chemicals that
  control the production of RNA. RNA in turn
  controls the production of proteins.
• The proteins either become part of the
  individuals body, or control the rate of
  chemical reactions in the body.

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• Figure 3.4
• The genes, composed of DNA, control the
  production of RNA, which in turn controls the
  production of proteins. Proteins form many
  structures of the body (e.g., muscles) they also
  control the rate of many chemical reactions
  (e.g., digestion).

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Genetic Principles

• Genes
• Cells that contained paired chromosomes also
  contain paired genes.
• If both genes of a pair are identical, the
  individual has received a homozygous pair.
• If the genes are different, the individual is
  heterozygous for that trait.

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• Figure 3.5
• In a pair of homozygous chromosomes, the gene for
  a given trait is identical on both chromosomes.
  In a heterozygous pair, the chromosomes contain
  different genes for a trait.

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Genetic Principles

• Genes
• If an individual receives one gene for wavy hair
  and another for straight hair, that individuals
  hair will be straight.
• The gene for wavy hair is a dominant gene. It is
  referred to as dominant because it will exert its
  effects even if the inheriting individual is
  heterozygous for the gene.

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Genetic Principles

• Genes
• A recessive gene will only show its effects in
  the homozygous condition. You must receive a gene
  for blue eyes from both parents in order to
  develop blue eyes.
• The gene for blue eye color is a recessive gene.

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Genetic Principles

• Genes
• An individual who is homozygous for a trait will
  always pass the dominant gene on to any
  offspring.
• An individual who is heterozygous for a trait may
  pass either the dominant or recessive gene on to
  the next generation.
• It is possible for parents who are heterozygous
  for a dominant trait to each pass a recessive
  gene to their child, who will then be homozygous
  for the recessive trait.

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Concept Check

• If you are wavy-haired but your brother has
  straight hair, are you homozygous or heterozygous
  for that trait, or is it impossible to say
  without looking at your genes?

It is impossible to say without genetic
testing. You could be homozygous or heterozygous
dominant.
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• What about your brother? What type of gene pair
  did he inherit?

Your brother must be homozygous recessive.
Recessive genes only exert influence in the
homozygous condition.
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• If both parents have blue eyes, what can we
  predict about their children?

Their children will have blue eyes too.
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Genetic Principles

• Sex-Linked Genes
• The sex chromosomes determine whether an
  individual will become a male or female.
• There are two types of sex chromosomes, called X
  and Y.
• Females receive an X from each parent males
  receive an X from mother and a Y from father.

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Genetic Principles

• Sex-Linked Genes
• Genes that are on the X-chromosome are called
  sex-linked genes.
• The influence of these genes is seen more often
  in men than in women.
• An example of such a trait is the disease
  hemophilia.

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• Figure 3.8
• Why males are more likely than females to be
  colorblind.

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Genetic Principles

• Sex-Linked Genes
• A man may have the gene on his X-chromosome.
  There is no gene on the Y, and so the trait
  manifests.
• A woman is much more likely to receive the
  dominant gene for normal blood clotting on one of
  her X-chromosomes, and not have the disease.

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Genetic Principles

• Sex-Linked versus Sex-Limited Genes
• Genes for the secondary sex characteristics
  (facial hair in men, breast development in women)
  are present in both sexes, but are activated by
  the presence of sex hormones.
• These are called sex-limited genes.
• Behavior differences between the sexes (such as
  the tendency for males to be more aggressive) are
  thought to be influenced by sex-limited genes.

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Concept Check

• A man who is colorblind marries a woman who is
  homozygous dominant for normal color vision. What
  is the likely outcome for any children they might
  have?

None of their children will be colorblind. The
daughters of the union will be carriers of the
condition.
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Genetic Principles

• Genetic screening
• Genetic diseases have been of great concern.
  Technology now allows us to identify and localize
  genes that cause such diseases.
• Some examples of these are
• Alzheimers Disease
• Huntingtons Disease
• Tay-Sachs Disease
• There are many others

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Genetic Principles

• Genetic screening
• Our ability to do this has led to some
  interesting ethical questions
• How does knowing this affect an individuals
  behavior (choice to have children, for example)?
• Should health insurers be able to know what a
  persons genetic make-up is? Would these
  companies deny coverage based on such knowledge?

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Genetic Principles

• Heritability
• Some traits are easily traced to a single gene.
• An example of such a trait is Huntingtons
  Disease. There are many others.

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Genetic Principles

• Heritability
• But even traits traced to a single gene may be
  strongly environmentally influenced.
• An example of this kind of gene is PKU. PKU
  causes profound mental retardation, but only if
  the affected persons diet includes foods
  containing a certain enzyme.
• If the person with the PKU gene is kept on a
  strict diet for the first two decades of life, he
  will have normal intelligence.

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Genetic Principles

• Heritability
• Many characteristics and conditions of interest
  to psychologists cannot be traced to a single
  gene.
• Mental processes and behaviors develop through
  complex interactions of the influences of genes
  and environment.
• In the case of traits such as addiction,
  personality characteristics, and intelligence, it
  is meaningless to ask if the trait depends solely
  on heredity or environment.

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Genetic Principles

• Heritability
• The concept of heritability helps us to rephrase
  the question to make it more useful.
• Does a difference in behavior or outcome depend
  more on differences in genetic make-up or
  differences in environment?
• Heritability is an estimate of the variance in a
  population that is due solely to heredity. If we
  could somehow make the environment the same for
  all individuals, the differences we would see
  would then be attributable to genetic differences.

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Genetic Principles

• Heritability
• Heritability is measured from 0 to 1.
• 0 means that almost none of the variance in the
  trait in due to heredity what religion a person
  practices has no basis in heredity.
• 1 signifies that variance in the trait is due
  entirely to heredity. If you have Huntingtons
  Disease or not will depend solely on whether you
  get the gene.

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Genetic Principles

• Heritability
• Many researchers have worked on the problem of
  heritability.
• It is difficult to know the exact degree of
  genetic influence because
• The environment can start to impact an individual
  right from conception (a mothers lifestyle and
  nutrition affect the growing fetus.)
• Environments are hard to standardize or make
  identical (except in the laboratory, perhaps.)

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Genetic Principles

• Heritability
• Evidence suggests that genetic factors contribute
  to variations in almost all behaviors and
  processes of interest to psychologists.
• But there are good reasons to suspect an
  overestimation of heritability in many
  psychological studies because of the difficulties
  involved in studying humans in their diverse
  environments.
• We need more evidence before we can confidently
  describe the role of heredity in forming human
  potential and personality.

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Concept Check

• If I raise 100 rats in identical laboratory
  environments and then test their maze-solving
  abilities, can I assume a high or low degree of
  genetic influence is responsible for differences
  in their abilities?

High Heritability is the index of genetic
influence when environment is held constant.
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Genetic Influences

• Some behaviors that have been shown to have a
  moderate degree of heritability
• Time spent watching TV
• Religious devoutness
• Dietary preferences
• These differences can be traced to biological
  factors that genes influence (activity levels,
  digestive chemistry.)

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Heredity and the Environment

• People believe that if a trait is found to be
  primarily genetically influenced (heritability
  1) nothing can be done to counteract its effects.
• But the example of PKU, described earlier, shows
  that a trait can be entirely under the influence
  of heredity, and yet also be easily influenced
  and altered by human intervention.

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Evolution and Behavior

• Our knowledge of genetics strongly supports the
  theory of evolution.
• An individual inherits genes that strongly
  influence its characteristics (offspring resemble
  parents.)
• Mutations, random changes in the structure of
  genes, occasionally cause offspring to differ
  from parents.
• Some genes may give certain individuals advantage
  in survival and reproduction. These individuals
  and their genes will increase in frequency in the
  population.

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• Figure 3.12Whats important for evolution is
  reproduction, not survival. Here the population
  starts with three people carrying trait A and one
  with trait B. The person with B and his or her
  descendants produce more children, on the
  average, than people with A do. Consequently, the
  genes controlling trait B will increase in
  prevalence from one generation to the next.

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Evolution and Behavior

• Natural Selection
• The changes in the frequencies of certain genes
  due to the above-described process are part of
  the process of evolution.
• Animal and plant breeders have been using these
  principles for centuries to create new strains
  through selective breeding or artificial
  selection.
• Darwins theory of natural selection proposes
  that the same results occur in nature.

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Evolution and Behavior

• Natural Selection
• If individuals with certain genetically
  controlled characteristics reproduce more
  successfully than others do, then future
  generations will come to resemble those
  individuals more and more.
• This is the principle of natural selection.

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Evolution and Behavior

• Natural Selection
• Many people misunderstand the phrase survival of
  the fittest to signify some type of physical
  strength, but fitness in Darwinian terms means
  successful reproduction a large number of
  offspring, in order to spread ones genes to
  future generations.

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Concept Check

• Infertile worker ants are sisters of the queen,
  the individual that lays all the eggs. In
  comparison to species where siblings are all
  fertile, would you expect ants to be more or less
  likely to sacrifice their lives to protect the
  queen?

More likely they are protecting their own
genetic investment.
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• Who is more fit in terms of natural selection
  a 30--year-old man who can run the mile in 4
  minutes, or a 32-year-old woman who has had 6
  children?

The woman -fitness means lots of offspring.
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Evolution and Behavior

• Understanding Evolution
• Other common misunderstandings include
• The idea that parts of an organism change as a
  result of use (or lack of it.) Evolution
  changes organisms only to the degree that
  certain characteristics are selected at a higher
  rate then others.
• The idea the evolution always means improvement.
• The selection of genes depends on the environment
  if the environment changes dramatically, a
  well-adapted species might suddenly find itself
  at a distinct disadvantage.

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Evolution and Behavior

• Sociobiology
• Sociobiology is a field that tries to explain the
  social behaviors of a species in terms of its
  biology and evolutionary history.
• An animal interacts with others in its species in
  certain ways that increase the probability of
  survival and reproduction.

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Evolution and Behavior

• Sociobiology
• For example, a sociobiological explanation of
  human sexual behavior suggests that men maximize
  their reproductive potential by mating with as
  many women as possible, while women jeopardize
  their possibility of having help in raising
  offspring if they mate with more than one man.

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Evolution and Behavior

• Sociobiology
• The result is that we have evolved sex-limited
  genes that influence men to pursue multiple
  partners and women not to do so.
• However, these differences in general do not
  confirm the existence of such genes. Cultural
  norms dictate these behaviors and it is hard to
  say to what degree these difference are learned.
• We will return to this issue later in the course.

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Genes, Evolution and Behavior

• Genes and environment interact in complex ways to
  bring about processes and behaviors of interest
  to psychologists.
• There is little basis on which to support the
  notion of genetic determinism, to believe that
  genes create immutable characteristics.
• Understanding exactly how genes exert effects
  gives researchers the best clues about how to
  modify the environment to maximized human
  potential.

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Module 3.2

• Neurons and Behavior

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Introduction

• Reductionism?
• Scientists in many fields use a strategy called
  reductionism they attempt to explain complex
  phenomena by reducing them to combinations of
  simpler components.
• Chemists use atoms and molecules physicists
  reduce the subatomic world to the interactions of
  a few fundamental forces.

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Introduction

• Reductionism?
• Does reductionism work in the science of
  psychology?
• Lets find out as we try to explain behavior in
  terms of the activity of the cells that comprise
  the nervous system.

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Nervous System Cells

• Neurons
• You experience yourself as a unitary entity.
• Neuroscientists have demonstrated that that
  experience is the product of a nervous system
  made up of an enormous number of discrete cells.
• The cells that make up your nervous system are
  called neurons.

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• Figure 3.14
• Distribution of the estimated 8386 billion
  neurons in the adult human central nervous
  system. (Based on data of R. W. Williams
  Herrup, 1988)

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Nervous System Cells

• The best current estimate is that the human
  nervous system has nearly 100 billion neurons.
• And they arent the only type of cell in the
  system.

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Nervous System Cells

• Glia
• Glia support the neurons in many ways.
• They provide insulation, and remove waste
  products and foreign bodies.
• They are 1/10th the size of the neurons, but
  about 10 times as numerous.

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Nervous System Cells

• Neurons and communication
• Neurons are a unique type of cell that can
  receive and transmit information
  electrochemically.
• Sensory neurons carry information from sense
  organs to the central nervous system.
• Neurons in the central nervous system process
  that information, interpret it, and then send
  commands to muscles, glands and organs.

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Nervous System Cells

• Anatomy of a neuron
• Neurons have a variety of shapes, but they all
  have 3 basic parts.
• A cell body that contains the nucleus and most of
  the organelles.
• The dendrites, widely branching structures that
  receive transmissions from other neurons.
• The axon, which is a single, long, thin fiber
  with branches near its tip.

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• Figure 3.16 
• The generalized structure of a motor neuron shows
  the dendrites, the branching structures that
  receive transmissions from other neurons, and the
  axon, a single, long, thin, straight fiber with
  branches near its tip. Axons range in length from
  1 millimeter to more than 1 meter and carry
  information to other cells. Inset A
  photomicrograph of a neuron.

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Nervous System Cells

• Axons
• The function of the axon is to send the
  electrochemical message on to the next cell.
• Most axons transmit information to the dendrites
  or cell bodies of neighboring neurons.
• Many axons in vertebrates (backboned animals)
  have a coating of myelin, which speeds up
  transmission.

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Nervous System Cells

• Nerve Impulses
• The electrochemical messages carried by neurons
  either increase or decrease the likelihood that
  the next cell will continue to transmit.
• Excitatory messages increase the probability that
  the next cell will fire - continue to carry the
  transmission.
• Inhibitory messages decrease the likelihood that
  transmission will continue to travel as in the
  case of the brain sending a message to inhibit
  pain in an injured extremity.

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Nervous System Cells

• Nerve cell growth
• Neurons do not have a fixed anatomy.
• Researchers have discovered that neurons are
  constantly growing and losing branches to
  dendrites and axons.
• This growth seems to be related to new
  experiences and learning.

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Nervous System Cells

• Nerve cell generation
• Neurons can be generated later in life (to a
  limited extent.)
• It was once thought that all neurons developed
  well before birth.
• Researchers have discovered stem cells -
  undifferentiated cells growing in some brain
  areas that are capable of developing into neurons
  in older organisms.

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Nervous System Cells

• Nerve cell generation
• Neuronal generation is generally very limited in
  scope.
• The action of stem cells seems to be stimulated
  after some types of brain damage, so their
  purpose may be in part compensatory.
• The growth of new neurons is much more limited
  than that which occurs in skin and hair cells.

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Nervous System Cells

• Action Potentials
• Axons convey information by a combination of
  electrical and chemical processes.
• This combination is called an action potential.
• An action potential is an excitation that travels
  along the axon at a constant strength regardless
  of the distance it must travel.

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The Neuron and Neural Impulse
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Nervous System Cells

• Action Potentials
• The all-or-none law
• An action potential is an all-or-nothing process
  its either happening or not theres no sort
  of action potential.
• This allows the message to reach the brain at
  full strength, but does slow it down compared to
  regular electrical conduction.

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Nervous System Cells

• Action Potentials
• How an action potential works
• An unstimulated axon has resting potential.
• Resting potential is an electrical polarization
  across the membrane covering the axon.
• A polarized axon has an inside charge that is
  negative (-70 millivolts) relative to the outside.

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Nervous System Cells

• Action Potentials
• How an action potential works
• Resting potential is maintained by the mechanism
  called the sodium-potassium pump.
• Sodium is mostly concentrated outside the neuron,
  and potassium mostly inside, and they are held in
  place by special gates while the polarization
  is maintained by the action of the pump.

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• Figure 3.17
• The sodium and potassium gradients for a resting
  membrane Sodium ions are concentrated outside the
  neuron potassium ions are concentrated inside.
  However, because the body has far more sodium
  than potassium, the total number of positive
  charges is greater outside the cell than inside.
  Protein and chloride ions (not shown) bear
  negative charges inside the cell. At rest, very
  few sodium ions cross the membrane except by the
  sodium-potassium pump. Potassium tends to flow
  into the cell because of an electrical gradient,
  and tends to flow out because of the
  concentration gradient.

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Nervous System Cells

• Action Potentials
• How an action potential works
• The sodium-potassium pump sends positively
  charged (1) sodium ions out of the cell and
  brings in a smaller number positively charged
  (1) potassium ions.
• The result is that the outside has more positive
  charges than the inside.

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Nervous System Cells

• Action Potentials
• How an action potential works
• When a message from a neighboring cell excites
  part of the axons membrane, some of the sodium
  gates are opened and sodium can enter the axon.
• This makes the charge inside the cell positive.
  Depolarization has taken place.
• The charge is now briefly the same inside and
  outside the cell. This is the action potential.

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• Figure 3.18
• Ion movements conduct an action potential along
  an axon. At each point along the membrane, sodium
  ions enter the axon and alter the distribution of
  positive and negative charges. As each point
  along the membrane returns to its original state,
  the action potential flows to the next point.

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• Figure 3.19 
• (a) During an action potential, sodium gates in
  the neuron membrane open, and sodium ions enter
  the axon, bringing a positive charge with them.
  (b) After an action potential occurs at one point
  along the axon, the sodium gates close at that
  point and open at the next point along the axon.
  When the sodium gates close, potassium gates
  open, and potassium ions flow out of the axon,
  carrying a positive charge with them. (Modified
  from Starr Taggart, 1992)

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Nervous System Cells

• Action Potentials
• How an action potential works
• The sodium gates shut very quickly and potassium
  gates open to allow potassium ions to leave the
  cell.
• These ions take positive charge out with them,
  and bring the axon back to a polarized state.
• Eventually the action of the sodium-potassium
  pump removes the excess sodium ions and
  recaptures the exiled potassium ions.

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Concept Check

• If a hamster and a seven-foot-tall human step on
  a sharp object, which will respond faster? Why?

The hamster, because the action potential has a
shorter distance to travel.
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Nervous System Cells

• Synapses
• Communication between neurons occurs at the
  synapses.
• A synapse is a specialized junction between two
  neurons where chemical messages cross from one to
  the other.
• The chemicals released by one will either excite
  or inhibit the other, making it either more or
  less likely to produce an action potential.
• This activity at the synapses is crucial to
  everything the brain does.

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• Figure 3.21
• The synapse is the junction of the presynaptic
  (message-sending) cell and the postsynaptic
  (message-receiving) cell. At the end of the
  presynaptic axon is the terminal bouton (or
  button), which contains many molecules of the
  neurotransmitter, ready for release.

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Nervous System Cells

• Synapses
• Synaptic communication
• Each axon has a bulge at the end called a
  presynaptic ending or a terminal bouton
  (alternately spelled button.)
• When the action potential reaches the terminal
  bouton, molecules of a neurotransmitter are
  released.
• A neurotransmitter is a chemical that is stored
  in the neuron. It activates special receptors of
  other neurons.

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Synaptic Transmission
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Nervous System Cells

• Synapses
• Synaptic communication
• Neurons use a variety of neurotransmitters, but
  each individual neuron always uses a particular
  neurotransmitter or combination of them.
• The neurotransmitter diffuses over the synapse to
  the surface of the receiving neuron (called the
  postsynaptic neuron.)
• The neurotransmitter attaches to receptors on the
  dendrite or cell body of the receiving neuron and
  either excites or inhibits it.

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• Figure 3.22
• The complex process of neural communication
  actually takes only 12 milliseconds.

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Nervous System Cells

• Synapses
• Synaptic communication
• After the neurotransmitter has excited or
  inhibited the receiving cell, it detaches from
  the receptor site, ending the message.
• The neurotransmitter may be reabsorbed by the
  axon that released (a process called reuptake) or
  diffuse away, be metabolized and removed from the
  body as a waste product, or remain the synapse
  and reattach to the receptor.

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Concept Check

• Learning and environmental challenges sometimes
  produce branching in axons and dendrites of an
  organisms neurons. How would that affect the
  number of synapses?

It would increase the number of synapses.
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• Dopamine is a neurotransmitter that excites
  postsynaptic neurons. If a drug were injected
  into an animal that blocked dopamine from
  attaching to its receptors, what would happen to
  the postsynaptic neurons?

They would be less likely to produce further
action potentials.
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Neurotransmitters and Behavior

• Our understanding of the role of
  neurotransmitters has revolutionized medicine,
  particularly psychiatry.
• A drug that can be designed to act on a
  particular kind of receptor in the nervous system
  can also have specific effects on an organisms
  functioning and behavior.
• It can be hypothesized that unusual behavior or
  problems in functioning may be due to lack or
  excess of a particular neurotransmitter.

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Neurotransmitters and Behavior

• Parkinsons Disease
• Parkinsons Disease is a condition in which the
  individual has trouble executing voluntary
  movements, and has tremors, rigidity and a
  depressed mood.
• This condition has been linked to a gradual decay
  in a system of axons that release the
  neurotransmitter dopamine.

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• Figure 3.24
•  With Parkinsons disease, axons from the
  substantia nigra gradually die. (a) Normal brain.
  (b) Brain of person with Parkinsons disease.
  Green 5 excitatory path red 5 inhibitory.

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Neurotransmitters and Behavior

• Parkinsons Disease
• Dopamine is a neurotransmitter that promotes
  activity levels and facilitated movement.
• Symptoms of Parkinsons Disease can be managed in
  mild cases with a drug called L-dopa, which is
  synthesized into dopamine by the neurons.

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Neurotransmitters and Behavior

• The link is not always so clear though.
• The symptoms of a disorder such as
  attention-deficit disorder or ADD include
  impulsive, agitated behavior and a short
  attention span.
• These symptoms would suggest an oversupply of
  dopamine.
• But there doesnt seem to be any relationship

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Concept Check

• People suffering from schizophrenia are given
  haloperidol, a drug that blocks activity at
  dopamine synapses. How would haloperidol affect a
  person with Parkinsons Disease?

It would make the symptoms worse.
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Neurotransmitters and Behavior

• The neurotransmitter, whether it is in over,
  under or normal supply, is just one part of a
  complex system.
• What alleviates the problem may not necessarily
  tell us what originally caused the problem.

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Module 3.3

• The Nervous System and Behavior

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The Major Divisions of the Nervous System

• The central nervous system and the peripheral
  nervous system
• The central nervous system consists of the brain
  and the spinal cord.
• The central nervous system communicates with the
  rest of the body via the peripheral nervous
  system.

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• Figure 3.25
• The nervous system has two major divisions the
  central nervous system and the peripheral nervous
  system. Each of these has major subdivisions, as
  shown.

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The Major Divisions of the Nervous System

• The central nervous system and the peripheral
  nervous system
• The peripheral nervous system is composed of
  bundles of axons between the spinal cord and the
  rest of the body.
• There are two sets of subdivisions of the
  peripheral nervous system.

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The Peripheral Nervous System

• The somatic nervous system and autonomic nervous
  system
• The somatic nervous system is made up of the
  peripheral nerves that communicate with the skin
  and muscles.
• The autonomic nervous system controls the
  involuntary actions of the heart, stomach and
  other organs.

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The Central Nervous System

• Embryological development
• During the embryonic stage, the vertebrate
  nervous system forms out of a simple tube with
  three lumps.
• The forebrain that becomes the cerebral cortex
  and other higher structures.
• The midbrain and hindbrain become the brainstem.
• The forebrain is especially dominant in human
  beings.

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• Figure 3.26 
• The human brain begins development as three
  lumps. By birth the forebrain has grown much
  larger than either the midbrain or the hindbrain,
  although all three structures perform essential
  functions.

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The Central Nervous System

• The Spinal Cord
• The Spinal Cord
• The spinal cord communicates with the body below
  the head by means of sensory and motor neurons.
• The sensory neurons carry information received by
  the senses from the extremities of the body to
  the spinal cord.
• The motor neurons transmit messages from the
  central nervous system to the muscles and glands.

99

• Figure 3.27
• The spinal cord receives sensory information from
  all parts of the body except the head. Motor
  nerves in the spinal cord send messages to
  control the muscles and glands.

100
The Central Nervous System

• The Spinal Cord
• The Spinal Cord
• Both reflex and voluntary responses are conducted
  through the spinal cord.
• A reflex is a rapid, automatic response to a
  stimulus. The spinal cord is usually the
  origination point of these responses.
• A voluntary response originates in the brain and
  travels through the spinal cord to the muscles
  needed to carry out the movements.

101
The Peripheral Nervous System

• The Autonomic Nervous System
• The Autonomic Nervous System
• A division of the peripheral nervous system that
  is closely associated with the spinal cord is the
  autonomic nervous system.
• The individual has very little control over the
  responses in this division, thus the name,
  autonomic.
• The autonomic nervous system has two subdivisions.

102
The Peripheral Nervous System

• The Autonomic Nervous System
• The Divisions of the Autonomic Nervous System
• The sympathetic nervous system is the crisis
  management center.
• It increases heart and respiration rate and
  prepares the body for fight or flight.
• A chain of neurons lying just outside the spinal
  cord controls it.

103

• Figure 3.28
• The sympathetic nervous system prepares the body
  for brief bouts of vigorous activity the
  parasympathetic nervous system promotes digestion
  and other nonemergency functions. Although both
  systems are active at all times, the balance can
  shift from a predominance of one to a
  predominance of the other.

104
The Peripheral Nervous System

• The Autonomic Nervous System
• The Divisions of the Autonomic Nervous System
• The parasympathetic nervous system is in charge
  of long-term survival related functions,
  nutrition and energy conservation.
• It decreases heart rate, increases digestive
  activities and promotes processes in the body
  that take place during rest.
• It is controlled by neurons at the upper and
  lower levels of the spinal cord.

105
The Endocrine System

• The Endocrine System is under the control of the
  nervous system.
• The endocrine system is a system of glands that
  release hormones into the bloodstream.
• Hormones are chemicals that affect mood, behavior
  and even anatomy.
• Some neurotransmitters act as hormones when
  released into the bloodstream. An example of one
  of these is epinphrenine, which is called
  adrenaline when it is acting as a hormone.

106

• Figure 3.29 
• Glands in the endocrine system produce hormones
  and release them into the bloodstream. This shows
  only some of the endocrine glands and some of
  their most abundant hormones.

107
Between the Spinal Cord and the Forebrain

• The hindbrain
• The medulla oblongata and the pons are two
  important structures in the hindbrain.
• They contain the axons that control breathing and
  heart rate.
• They are also in charge of relaying sensory
  information from the head and sending motor
  messages back to it.

108
Between the Spinal Cord and the Forebrain

• The hindbrain
• The cerebellum is important for coordination and
  timing.
• It is also in charge of tasks that requiring
  shifting of attention and discrimination between
  stimuli.

109

• Figure 3.30
• (a) The major divisions of the human central
  nervous system, as seen from the midline.

110

• Figure 3.30 Cont.
• (b) A side view of the brain, showing internal
  structures as though the cerebral cortex were
  transparent.

111
Between the Spinal Cord and the Forebrain

• The hindbrain midbrain
• The medulla, pons and midbrain contain the
  reticular activating system (or reticular
  formation.)
• This structure regulates levels of arousal in the
  brain.

112
The Forebrain

• The limbic system
• The limbic system is comprised of three major
  structures.
• The hippocampus is crucial for memory
  consolidation.
• The hypothalamus, which drives the endocrine
  system and regulates hunger, thirst and sexual
  desire.
• The amygdala, which is important for generating
  emotional and motivated behaviors.

113
The Forebrain

• General structure
• The Forebrain
• The forebrain has two separate hemispheres, left
  and right.
• Each hemisphere controls sensation and motor
  functioning on the opposite side of the body.
• The hemispheres of the brain communicate with
  each other through a thick bundle of axons
  crossing between them, called the corpus callosum.

114
The Forebrain

• Cerebral Cortex
• The cerebral cortex
• The outer covering of the forebrain is known as
  the cerebral cortex.
• It is made up of the gray matter, the cell bodies
  of the cortical neurons.
• The interior of the forebrain is made up of white
  matter or axons of cortical neurons. It is white
  because of the myelin that coats axons.

115
The Forebrain

• Cerebral Cortex
• The four lobes of the cerebral cortex
• Its customary to represent the areas of the
  cerebral cortex as four lobes occipital,
  parietal, temporal, and frontal.
• The occipital lobe is at the rear of the head,
  and contains many specialized areas for
  interpreting visual sensory information.
• There are areas both inside and outside the
  occipital lobes for shape, color and motion
  vision.

116

• Figure 3.33 
• The four lobes of the human cerebral cortex, with
  indications of some of their major functions.

117
The Forebrain

• Cerebral Cortex
• The four lobes of the cerebral cortex
• The parietal lobe is directly in front of the
  occipital lobe.
• It contains the primary somatosensory cortex, the
  area of the brain that is specialized for body
  senses and awareness of the location of body
  parts.

118
The Forebrain

• Cerebral Cortex
• The four lobes of the cerebral cortex
• The temporal lobes are located on the sides of
  the head, near the ears.
• They are the main processing areas for hearing
  and complex aspects of vision. The hippocampus
  and amygdala are deep inside the temporal lobes.
• The left temporal lobe contains important
  language processing areas.

119
The Forebrain

• Cerebral Cortex
• The four lobes of the cerebral cortex
• The frontal lobes are at the front of the brain.
• They contain the primary motor cortex, and area
  that is important for control of fine movements.
• The foremost part of the frontal lobes, the
  prefrontal cortex, is responsible for
  organization, planning of action, and aspects of
  memory.

120
Concept Check

• Which lobe is damaged if
• A person is unable to feel or locate the left
  side of her body?

Right parietal lobe
121

• Which lobe is damaged if
• A person has difficulty with fine movements with
  the right hand?

Left frontal lobe
122

• Which lobe is damaged if
• A person has loss of vision in the right visual
  field?

Left occipital lobe
123

• Which lobe is damaged if
• A person has impaired emotional experience and
  some hearing loss?

Temporal lobe
124
Imaging the brain

• Methods for looking at and mapping the brain
  include
• Computerized axial tomography (CT or CAT
  scanning), passes x-ray through the head while
  dye is present in the blood stream. This allows
  viewing of anatomical structures.
• CAT scans do not allow the viewing of brain
  activity.

125
Imaging the brain

• Methods for looking at and mapping the brain
  include
• Positron emission tomography (PET) provides a
  high-resolution picture of brain activity using
  radioactivity from chemicals injected into the
  bloodstream.
• The color of the image indicates the level of
  activity, red areas are most active, followed by
  yellow, green and blue for the least active
  areas.
• PET scans provide fascinating information, but
  are expensive and can be risky to the subject.

126
Imaging the brain

• Methods for looking at and mapping the brain
  include
• Functional magnetic resonance imaging (fMRI) uses
  magnetic detectors outside the head to measure
  the amounts of hemoglobin and oxygen in different
  areas of the brain.
• Highly active areas of the brain appear to use
  more oxygen in fMRI images.

127
Experience and the brain

• Learning changes the brain
• We now know, because we can see the brain, and
  its activity that practicing behaviors (learning
  to play a musical instrument, for example) can
  change the structure of the brain by altering the
  cortical neurons.

128
Experience and the brain

• The binding problem
• We still dont understand precisely how all the
  different parts of the brain allow us to have a
  unified experience of objects or events, since
  the areas of the brain that help us analyze our
  experience are often not directly connected to
  each other.
• It is amazing that people can lose just one
  aspect of vision, for example, color, motion, or
  the ability to recognize faces.

129

• Figure 3.34
• (a) Locations of the primary somatosensory cortex
  and the primary motor cortex.

130

• Figure 3.34 Cont.
• (b) The primary somatosensory cortex and...

131

• Figure 3.34 Cont.
• (c) the primary motor cortex, illustrating which
  part of the body each brain area controls. Larger
  areas of the cortex are devoted to body parts
  that need to be controlled with great precision,
  such as the face and hands. The figure shows the
  left primary somatosensory cortex, which receives
  information from the right side of the body, and
  the right primary motor cortex, which controls
  the muscles on the left side of the body. (b and
  c after Penfield Rasmussen, 1950)

132
Experience and the brain

• The two halves of the brain
• Work with individuals who have had the
  split-brain operation (severing the corpus
  callosum) to control seizures provides evidence
  that the two hemispheres are highly specialized.
• The right hemisphere needs to communicate with
  the left in order to name the objects in its
  visual field.
• The left hemisphere needs the right in order to
  synthesize details into a whole picture (the
  parts of a face into a whole recognizable image.)

133

• Figure 3.42 
• The corpus callosum is a large set of axons that
  convey information between the two hemispheres of
  the cerebral cortex. (a) A midline view showing
  the location of the corpus callosum. (b) A
  horizontal section showing how each axon of the
  corpus callosum links one spot in the left
  hemisphere to a corresponding spot in the right
  hemisphere.

134

• Figure 3.43 
• In the human visual system (viewed here from
  above), light from either half of the world
  crosses through the pupils to strike the opposite
  side of each retina. Axons from the left half of
  each retina travel to the left hemisphere of the
  brain axons from the right half of each retina
  travel to the right hemisphere of the brain.

135

• Figure 3.44
• (a) A woman with a severed corpus callosum cannot
  name something she sees in her left visual field
  but can find the corresponding object with her
  right hand.

136

• Figure 3.44 Cont.
• (b) When the word hatband is flashed on a screen,
  a woman with a split brain can report only what
  her left hemisphere saw, band. However, with her
  left hand she can point to a hat, which is what
  the right hemisphere saw.

137
Right Brain Left Brain
Please choose the button below that corresponds
to the type of operating system you are using
138
The brain and the self

• We are still learning about the brain, but we now
  understand that your brain is composed of many
  separate areas with separate abilities.

139
The brain and the self

• If you lose part of the brain, you lose part of
  your unique experience.
• Brain activity and mind are inseparable, one is
  the other.