Download intro to psych ch3 biological bases of behavior

Introduction to Psychology
Chapter 3: The Biological Basis
of Behavior
Nervous System
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CNS: Brain and Spinal Cord
Peripheral Nervous System:
network of nerves that carries
information to and from the nervous
system
Nervous System
Nervous System
CNS
Peripheral NS
Somatic
Sympathetic
Autonomic
Parasympathetic
Peripheral Nervous System
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Somatic System: carries messages to
and from sense organs and skeletal
muscles
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Controls voluntary behavior
Peripheral Nervous System
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Somatic system:
Afferent nerve fibers carry info from the
body to the nervous system
Efferent nerve fibers carry info from the
nervous system to the body
Peripheral Nervous System
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Autonomic Nervous System: glands
and organs; “automatic functions”
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Heartbeat, digestion
Peripheral Nervous System
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Sympathetic: fight or flight; prepares
for action
Parasympathetic: quiets the body;
lowers arousal
Neurons
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Nerve cells in the brain
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Carry messages; activate muscles and
glands
100 billion neurons in the brain
The Neuron
Fig. 3.8
Parts of the Neuron
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Dendrites: receives messages from
other neurons
Soma: receives messages; sends nerve
impulse down the axon
Parts of the Neuron
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Axon: thin fiber leading to the terminal
buttons; nerve impulses travel down the
axon; carries messages
Myelin sheath: fatty layer covering the
axon that helps nerve impulses move
faster
Parts of the Neuron
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Synapse: the microscopic space
between the neurons over which
messages pass
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Neurotransmitters travel across the axon
Ions: electrically charged molecules found inside
and outside the neuron, with + or - charges
Resting Potential
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Electrical charge of an inactive neuron
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-70 mv
Messages from other neurons raise or
lower the resting potential
Threshold
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If the charge raises to -50 mv, the
neuron reaches its threshold
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Threshold=trigger point for firing
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Ready to fire
Neural Firing
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An action potential (nerve impulse)
sweeps down the axon
Ion channels open and sodium ions rush in
After the action potential....
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Positive ions flow back out; the neuron
becomes negatively charged again
Resting state is restored
After firing, the neuron dips below
resting level and is less willing to fire
Firing...
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Firing is an all or nothing event
The neuron either fires, or doesn’t fire
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It take 1/1000 of a second for a neuron to
fire; on average, they fire between 1-400
times per second
Neurotransmitters
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Chemicals that alter activity in the
neurons
Travel from terminal buttons across
synapse

connect to special receptors sites
dendrites/soma of next neuron
Neurotransmitters
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Neurotransmitters can excite or inhibit
firing
Types of Neurotransmitters
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Dopamine: too little=Parkinson’s, too
much=schizophrenia
Acetylcholine: activates muscles
Serotonin: deficiency associated with
depression/anxiety
Neuropeptides: influence memory, pain,
emotion, and mood
Endorphins: released by the pituitary glad;
lessens pain
The Brain
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Right and Left hemispheres
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Lateralization
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Divided by the corpus callosum
Left Hemisphere
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Detail oriented
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Speech and language
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Calculating
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Understands one word at a time, not the big
picture
Right Hemisphere
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Non-verbal
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Face recognition
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Express/detect emotion
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Understanding speech context/nuances of
language
The Brain’s Four Lobes
Fig. 3.7
Functions of Lobes of the Cortex
Frontal lobes
Involved in voluntary movement,
thinking, personality, and
intentionality or purpose
Occipital lobes Function in vision
Temporal lobes
Parietal lobes
Active role in hearing, language
processing, and memory
Roles in registering spatial location,
attention, and motor control
The Brain
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Recent research:
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Both heredity and environment shape the
brain
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The role of experience and brain plasticity
Dendritic Spreading
Fig. 3.11
Experience and the Brain
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Exposure to trauma:
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Depression:
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PTSD: reduced size of the hippocampus
Parts of the brain atrophy over time
Addiction:
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Changes in neurotransmitters
Experience and the Brain
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Children reared in deprived
environments have depressed brain
activity (i.e. Romanian orphans)
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Can be reversed; brain plasticity/resilience
DNA, Chromosomes, and
Genes
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Chromosomes: in the nucleus;
threadlike structures that contain DNA
DNA: contains genetic instructions
Genes: unit of hereditary information;
each has its own function and location
Nucleus (center of
cell) contains
chromosomes
and genes
Fig. 2.3
Chromosomes are
threadlike structures
composed of DNA
molecules
Gene: a segment of DNA
(spiraled double chain)
containing the hereditary
code
Polygenetic Inheritance
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Polygenetic Inheritance: when many
genes interact to influence a characteristic
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Behavioral traits are caused by several genes
(and the environment)
Genes
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Human Genome Project:
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Humans have 20,000-25,000 genes
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All humans: genes are 99.9% the same
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Humans and apes share 96-98% of their
genes
Nature vs. Nurture
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Nature: the role of genes
Nurture: the role of the environment and
external conditions
**Interactionist Perspective: Both
nature and nurture shape development
Behavioral Genetics
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A field that looks at the influence of
heredity and environment
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Twin studies: comparing identical and
fraternal twins
Adoption studies: are children more
similar to the biological or adoptive
parent?
Twin Studies
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Identical Twins share 100% of their
genes
Fraternal/non-twin siblings share 50%
of their genes
Twin Studies
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We compare identical and fraternal
twins
If identical twins are more similar than
fraternal twins, we can make the case
for heredity
Adoption Studies
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If adopted children are more similar to
biological parents, we can make the
case for heredity
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More similar to adoptive parents: case for
environment