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Chapter 2: Biological Foundations of Behavior

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Title: Chapter 2: Biological Foundations of Behavior


1
Chapter 2 Biological Foundations of Behavior
  • Michael L. Farris
  • Psychology 101

2
Nervous System
  • Autonomic nervous system - The division of the
    nervous system that regulates the bodys inner
    environment (heart rate, blood pressure,
    digestion, pupil dilation, and electrical
    conductance of the skin.) Pgs. 50-51.
  • Afferent Nerves (advance, arrive, approach)
    carry sensory signals from internal organs TO the
    CNS (brain and spinal cord). Up. p.40.
  • Efferent nerves (Exit, Embark, Escape p. 52)
    carry motor signals away from the central nervous
    system TO the skeletal muscles. Down. P.41.
  • Afferent and efferent nerves are also known as
    sensory neurons (p. 40).

3
The Blood-Brain Barrier
  • Blood-Brain Barrier (Pinel, p. 55) The brain
    is a finely tuned electrochemical organ whose
    function can be severely disturbed by the
    introduction of certain kinds of chemicals.
  • Fortunately, there is a mechanism that impedes
    the passage of many toxic substances from the
    blood into the brain the blood-brain barrier.

4
The Brain Stem
  • Brain Stem The part of the brain on which the
    cerebral hemispheres rest in general, it
    regulates reflex activities that are critical for
    survival (heart rate and respiration). The Brain
    Stem (particularly the medulla) regulates basic
    life functions (heart rate and breathing, and
    such reflexes as swallowing, coughing, and
    sneezing). P. 53.

5
Cerebral Hemispheres, Corpus Callosum
  • The brain is composed of two sides, or
    hemispheres.
  • Left Brain Controls language, speech, writing,
    calculation, time sense, rhythm, and the ordering
    of complex movements.
  • Right Brain Non-verbal. Controls perceptual
    skills, visualization, recognition of patterns,
    faces, and melodies, recognition and expression
    of emotion, spatial skills, and simple language
    comprehension.
  • The left and right hemispheres are joined
    together by the Corpus Callosum, a structure in
    the middle of the brain that enables hemispheres
    to share functions and information.
  • Please see pages 54-54 in your text for more
    information.

6
Case Studies
  • Studies that focus on a single case or
    subject.
  • Detailed
  • In-depth
  • Pro Good source of testable hypotheses.
  • Con not very easy to generalize to others.
  • Humans differ be skeptical of any
    biopsychological theory based on only a few case
    studies. P.23.
  • Example Lobotomy (1 primate study)

7
CNS and Cerebral Cortex
  • Central Nervous System (CNS) The portion of the
    nervous system within the skull and spine.
  • Composed of 2 divisions Brain and Spinal Cord.
  • Cerebral Cortex - The layer of neural tissue
    covering the cerebral hemispheres of humans and
    other mammals. Being the OUTER layer, it is most
    likely to be damaged by accident or surgery.
  • Please see pages 47-50 for more information.

8
Thinking and Learning
  • Cerebrum - The portion of the brain that sits
    on the brain stem in general, it plays a role in
    complex adaptive processes (like learning,
    perception, and motivation). P.54.
  • Cognition - Complex intellectual processes such
    as thought, memory, attention, and perceptual
    processing. p.11.

9
Comparative Psychology
  • Comparative Psychology - The division of
    Biopsychology that studies the
  • evolution, genetics, and adaptiveness of
    behavior, often by using the comparative
  • method (The study of biological processes
    by comparison of different species). P.15.

10
Convolutions
  • Folds on the surface of the cerebral
    hemispheres.
  • Folds have increased over time
  • greatly increased the volume of the cerebral
    cortex (the outermost layer of cerebral tissue).
  • More surface area more capacity

11
DNA, EEG, and Evolution
  • Deoxyribonucleic acid (DNA) Double Stranded,
    coiled molecules of genetic material. The basic
    chemical material in chromosomes that carries the
    individuals genetic code. (p.72).
  • Electroencephalograph (EEG) - A measure of the
    general electrical activity of the brain, often
    recorded through the scalp. Pgs. 58-59.
  • Evolve - To undergo gradual orderly change. P.10.

12
Myelin
  • Myelinated Nerves carry signals 200 times FASTER
    than unmyelinated ones.
  • (Axons vary in length from 0.04 inches to 1
    yard.)
  • The fastest nerve signals travel at over 250 mph.
  • Nerve signals enter a neuron through its
    dendrites and rush along the axon. At the far
    end, called the nerve-ending, the axon has other
    dendrites that pass the message on to the
    dendrites of other neurons.
  • Neurons that have to carry urgent signals over
    long distances are surrounded by thick insulation
    to keep the signal strong, in the same way that
    the cable from a TV aerial to the TV is coated
    with insulating plastic.
  • In the case of neurons, the insulation is a
    myelin sheatha series of long, flat cells
    wrapped around the axon. In people with the
    crippling disease multiple sclerosis, the sheaths
    break down, weakening the nerve signals. Pgs.
    41-42.

13
Natural Selection
  • Heritable traits that are associated with
    high rates of survival and reproduction are
    preferentially passed on to future generations.
    (No magic here simply good traits get
    reproduced.)
  • For example, fast horses are selected and
    bred by racehorse breeders, so each succeeding
    generation gets faster overall. The slow ones
    dont get a chance to reproduce and pass on their
    slower genes. Nature is similar. The slow fish
    cant outrun the shark, so doesnt get to
    reproduce.

14
Nature/Nurture and PNS
  • Nature-nurture issue - The debate about the
    relative contributions of nature (genes) and
    nurture (experience) to the behavioral capacities
    of individuals. Pgs. 72-73.
  • Peripheral Nervous System (PNS) The division
    located outside the skull and spine. Composed of
    2 divisions
  • Somatic nervous system (SNS) (the part of the PNS
    that interacts with the external environment)
  • Autonomic nervous system (ANS), the part which
    participates in the regulation of the internal
    environment. Pgs. 47-49.

15
Lobotomy and Spinal Cord
  • Prefrontal Lobes - The large areas, left and
    right, at the very front of the brain.
  • Prefrontal Lobotomy - A surgical procedure in
    which the connections between the prefrontal
    lobes and the rest of the brain are cut as a
    treatment for mental illness.
  • Spinal Cord comprises 2 different areas
  • Gray Matter (composed largely of cell bodies and
    unmyelinated interneurons)
  • White Matter (composed largely of myelinated
    axons.) It is the myelin that gives the white
    matter its glossy white sheen.

16
Sympathetic and Parasympathetic Nerves
  • Sympathetic nerves stimulate, organize, and
    mobilize energy resources in threatening
    situations. Sympathetic changes are indicative of
    psychological arousal.
  • Parasympathetic nerves act to conserve energy.
    Parasympathetic changes are indicative of
    psychological relaxation (think of a parachute).
  • Each autonomic target organ receives opposing
    sympathetic and parasympathetic input, and its
    activity is thus controlled by relative levels of
    sympathetic and parasympathetic activity. P.51.

17
Brain Anatomy
  • Early brain development 3 sections form
    (forebrain, midbrain, and hindbrain).
  • Later, these grow into five major different
    swellings (telencephalon, diencephalons,
    mesencephalon (midbrain), metencephalon, and
    myelencephalon).
  • ENCEPHALON means within the head. In humans,
    the telencephalon (right and left cerebral
    hemispheres) undergo the greatest growth during
    development.
  • The other 4 divisions are often referred to
    collectively as the Brain Stem, on which the
    cerebral hemispheres sit. The myelencephalon is
    often referred to as the medulla.
  • Again Brain Stem myelencephalon,
    metencephalon, mesencephalon, and
  • diencephalon. 4 of 5 divisions are in the
    stem.

18
Brain and Spine Protectors
  • Meninges, Ventricles, and Cerebrospinal Fluid
    (Pinel p. 53) The brain and spinal cord (the
    CNS) are the most protected organs in the body.
    They are encased in bone and covered by three
    protective membranes, the meninges.
  • Also protecting the CNS is cerebrospinal
    fluid, which fills the central canal of the
    spinal cord and the cerebral ventricles of the
    brain. It also fills the subarachnoid space,
    which contains many large blood vessels.
  • The cerebral ventricles are the four large
    internal chambers of the brain 2 lateral
    ventricles, the third ventricle, and the fourth
    ventricle. It is believed that the ventricles
    are often enlarged in people with schizophrenia.

19
Neural Conduction and Synaptic Transmission
  • Neural ConductionElectrical (the way a nerve
    impulse travels along a nerve cell.
  • Synaptic TransmissionChemical (the way
    neurotransmitters travel across the synapse (gap)
    to communicate with another nerve cell (neuron).

20
Neural Conduction/Synaptic Transmission
  • Nerve signals are constantly whizzing from neuron
    to neuron all around your body yet no two
    neurons ever actually touch. Instead, there is a
    small gap between connecting neurons called a
    synapse.
  • When a nerve signal is passed on from one neuron
    to the next, it is carried across the gap by
    special chemicals called neurotransmitters. The
    chemicals are released by the neuron that is
    sending the signal.
  • Droplets of neurotransmitters are stored inside
    the nerve-ending in tiny sacs called vesicles.
    When a nerve signal arrives at the nerve-ending,
    the vesicles drift towards the synapse and spill
    out their contents into the gap. The
    neurotransmitters flood across the gap and wash
    up against the other nerve. Inside every nerve
    ending are sacs of chemical transmitters. These
    are released into the synapse when the nerve is
    activated, or excited, by a nerve signal. If
    the adjoining nerve has the right receptors (page
    95), the signal will pass on.

21
Neural Conduction and Synaptic Transmission
  • The term exocytosis (Pinel pages 94-95) refers to
    the process of releasing a neurotransmitter.
  • Neurotransmitter chemicals work a bit like keys
    in locks. In this case, the locks are special
    receptor sites in the dendrites of the receiving
    neuron.
  • These sites accept only one kind of chemical.
    For the nerve signal to pass on, the
    neurotransmitter must be the right chemical that
    fits, or unlocks, the receptor site. If the
    neurotransmitter fits, it changes the chemistry
    of the receiving nerves membrane (skin). This
    starts off the electrical charges that pass the
    signal along the length of the neuron.
  • Because a receptor site responds only to one type
    of neurotransmitter, an active nerve will pass on
    the signal only to neurons that have the right
    receptors, even though it is linked to many
    others. Pgs.40,43-44.

22
Excitation and Inhibition
  • Different types of signals follow different
    routes through the body.
  • If every single nerve signal were passed on by
    every single synapse, you would simply be
    overwhelmed by nerve signals. This is why at
    some synapses the receiving neurons react by
    passing on the signal, but at others they react
    by blocking it.
  • This is called excitation and inhibition.

23
Neurotransmitters
  • There are more than 40 different
    neurotransmitters
  • Noradrenaline helps to control heartbeat and
    blood flow
  • Dopamine works in the areas of the brain that
    control movement and coordination (when youre
    making a tricky move on a skateboard, your nerve
    endings are releasing lots of dopamine, a
    neurotransmitter that helps muscles move more
    easily).
  • Endorphins are used by the brain to control pain
    (they are called endogenous opiatesliterally,
    opiumlike chemicals that are produced within the
    body see page 100 for more information).
  • Acetylcholine is involved in making muscles
    contract
  • When you wake up in the morning, it is because
    certain nerves are flooding your brain with the
    neurotransmitter serotoninand any nerve that is
    receptive gets an alarm call!
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