Transcript No Slide Title

Psychology 110B
Introduction to Neurons
The stuff of the brain and mind
© Kip Smith, 2003
Review
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Nervous system
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Central
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Spinal cord
Brain
• Cortex, etc
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Peripheral
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Sensory
Motor
• Autonomic
• Skeletal
© Kip Smith, 2003
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Cerebral cortex
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4 lobes
2 hemispheres
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Motor area
Sensory areas
Association areas
Review
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Perception &
cognition
Connects the
hemispheres
Limbic system
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© Kip Smith, 2003
Drives
Memory
Emotion
Sensory relay
station
Rapid motion
Life support &
homeostasis
Functional
differentiation
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Cortical regions with
specialized functions
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Motion
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Speech production
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Modulation of
emotion
Speech
comprehension
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Hearing
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Vision
© Kip Smith, 2003
Topographic organization
Hemispheric asymmetry of
‘higher’ functions
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Left
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Language
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Broca’s area
Wernicke’s area
Putting it all together
© Kip Smith, 2003
Right
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Visuospatial
Faces
Maps
Neuroimaging
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Goal: discover, identify, and take pictures
of the regions of the brain that are
actively supporting mind and behavior
The underlying assumption
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Active neurons require nourishment
Blood  oxygen, hemoglobin, sugars, etc.
More activity, more bloodflow
Measure bloodflow, infer neural activity
© Kip Smith, 2003
PET
Positron Emission Tomography
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Radioisotopic tracer injected into bloodstream
Oxygen 15 decays to Nitrogen + a positron
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Half-life 80 seconds
Positron annihilates an electron
Reaction generates 2 gamma rays travelling in
opposite directions
© Kip Smith, 2003
PET
Positron Emission Tomography
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Patterns of gamma ray emissions locate where
isotope decayed
Density of decay is proportional to bloodflow
More bloodflow is inferred to reveal more
neural activity
© Kip Smith, 2003
Neuroimages using PET
fMRI Functional Magnetic
Resonance Imagery
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A strong external magnet polarizes iron
ions in hemoglobin
The polarized ions create a secondary,
induced magnetic field
and radio waves
at characteristic
frequencies
© Kip Smith, 2003
Neurons
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The elementary units of the information
processing system
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Integrate and transmit pulses of electrical
charge
Are linked by chemical neurotransmitters
© Kip Smith, 2003
A neuron & its parts
Myelin sheath
Soma
(cell body)
Axon
Dendrites
© Kip Smith, 2003
Terminal
Buttons
Neural communication
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Neurons form chains and networks
through which they send packets of
information
© Kip Smith, 2003
Neural communication
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Neurons form chains and networks
through which they send packets of
information
© Kip Smith, 2003
Neural communication

Neurons form chains and networks
through which they send packets of
information
© Kip Smith, 2003
Neural communication

Neurons form chains and networks
through which they send packets of
information
© Kip Smith, 2003
Key terms in
neural communication
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Terminal button
Neurotransmitters
Synapse
Dendrite
Soma, cell body
Axon
Myelin
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© Kip Smith, 2003
Excitatory connection
Inhibitory connection
Activation level
Threshold
Repolarization
Action potential
Depolarization
Spreading activation
Plasticity
Graded chemical communication
Neurotransmitters
Terminal Button
Dendrite
Soma
Synapse
© Kip Smith, 2003
Neurotransmitters
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© Kip Smith, 2003
Hundreds of neurons
release chemical
neurotransmitters that
adhere to the dendrites of
a target neuron
Glutamate
Acetylcholine
Dopamine
Serotonin
Norepinephrine
...
Excitatory connections
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© Kip Smith, 2003
Excitatory connections
increase the rate of
firing of the target
neuron
Inhibitory connections
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© Kip Smith, 2003
Inhibitory connections
decrease the rate of
firing of the target
neuron
Chemical communication between neurons
at the synapse becomes
electrical communication within the neuron
Axon
Soma
© Kip Smith, 2003
Myelin
Activation
&
Threshold
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© Kip Smith, 2003
The target neuron
accumulates these
packets of information
The accumulation is
called its activation
level
The threshold is its
limited capacity for
information
Repolarization
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© Kip Smith, 2003
When the amount of
information reaches its
threshold, (i.e, when it ‘fills
up’ with information),
it becomes fully (re)polarized
and generates an action
potential, a brief quantum of
electrical charge that travels
down its axon to its terminal
buttons
Action potential
The action potential
is a quantum (an
all-or-nothing unit )
of electric charge
The charge
travels down the
axon to the
terminal buttons
© Kip Smith, 2003
Depolarization
The cell body
depolarizes when
the action potential
travels down the axon
to the terminal buttons.
© Kip Smith, 2003
From electrical communication
within the neuron to
chemical communication at the synapse
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When the action
potential reaches the
terminal buttons, they
release chemical
neurotransmitters
across the synapse
with the the next
target neuron
Information flows from
one neuron to the next
© Kip Smith, 2003
Neural communication
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The transmission of information is known
as spreading activation
© Kip Smith, 2003
The brain is a neuronal
information processing system
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Billions of neurons
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that are arrayed in networks &
energized by spreading activation
The neural networks form specialized
regions with
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Topographic organization
Highly precise interconnections
Localization of function
© Kip Smith, 2003
Neuronal plasticity
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Learning causes neurons to develop new
neurons and more terminal buttons and to
make more synaptic connections
This plasticity
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Is most rapid in young children
Is most evident in the hippocampus
Declines with age
© Kip Smith, 2003
Summary
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Information is represented in patterns of
spreading activation across interconnected
networks of neurons
Localization of function:
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Different parts of the brain contain networks of
neurons that process different types and
sources of information and direct different
behaviors
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© Kip Smith, 2003
Limbic system => Emotion
Frontal cortex => Reason, judgment
The brain is the most complex
thing we know about
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Normal behavior requires all the parts to
work together
Multiple patterns of spreading neural
activation must interact seamlessly
It usually works.
Sometimes it doesn't:
© Kip Smith, 2003
Psychoactive drugs
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Either enhance or block synaptic transmission
Three mechanisms
© Kip Smith, 2003
At the terminal button
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Either facilitate the release of the neurotransmitter
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Speed, cocaine
Or inhibit the release of the neurotransmitter
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Antipsychotics
© Kip Smith, 2003
Within the synapse
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Either facilitate the reuptake of the neurotransmitter
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Or inhibit the reuptake of the neurotransmitter
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Clinical antidepressants, Zoloft (?)
© Kip Smith, 2003
At the dendrite
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Either block access
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Caffeine (blocks inhibitory connections)
Or act like a neurotransmitter
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© Kip Smith, 2003
LSD, psilocybin,nicotine,
Valium (increases inhibitory connections)
Questions?
© Kip Smith, 2003