Transcript Ch 3 Power Point

Chapter 3: The Biological
Bases of Behavior
The nervous system is the body’s
communication network
Behavior depends on rapid information
travel and processing…the nervous system
is the body’s 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 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.
Figure 3.1 Structure of the neuron
The Neural Impulse:
Electrochemical Beginnings
• Hodgkin & Huxley (1952) - Alan Hodgkin
and Andrew Huxley in the 1950’s discovered
the mechanics of neural transmission by
studying giant squid…which 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 doesn’t. 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 don’t 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
Figure 3.3 The synapse
When a Neurotransmitter Binds:
The 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 fire…decreases 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.
Figure 3.4 Overview of synaptic transmission
Signals: From Postsynaptic Potentials
to 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 cell’s 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
Signals: From Postsynaptic Potentials
to 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
Signals: From Postsynaptic Potentials
to 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.
Figure 3.5 Synaptic pruning
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
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 (Parkinson’s, 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 systems
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 body’s resources
for emergencies and creates the fight-or-flight
response
• Parasympathetic: activates processes that
conserve bodily resources…slowing heart rate,
reducing blood pressure, etc
Figure 3.6 Organization of the human nervous system
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 Xray
– 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
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)
– Parkinson’s 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 cerebrum
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 hemispheres
– 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 brain
Right Brain/Left Brain
• Broca’s Area: left frontal lobe; plays an
important role in the production of speech
• Wernicke’s 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 exhibited
• Left Hemisphere: better at verbal stimuli
(lang., speech, reading, and writing), positive
emotions exhibited
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 hormone
• 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 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
Genes and Behavior:
The 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
person’s genetic makeup (lifelong), while
phenotype refers to the ways in which a
person’s genotype is manifested in
observable characteristics (variable)
• Polygenic Inheritance: most human traits
are not so simple with regard to genetic
transmission…they 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 alikeenvironment 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 personality
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 modelpeople 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 Darwin’s ideas of:
– Natural selection
• Successful transmission of genetic
evolution depends on providing either a
reproductive advantage (firefly’s 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 foods…this was
adaptive in a hunter/gatherer society, when
dietary fat was scarce
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!