Dr. Nega's PPT notes for course AP 5001 Fundamentals of Psycholoy Science DEREE-The American College of Greece

1. Week 3:
Definition of Action Potential in Psychology
Dr. Chrisanthi Nega, PhD
AP 5001 Fundamentals of Psychology Science
Image sources:
• Images 1 -2: http://imgarcade.com/1/action-potential
• Image 3: http://galleryhip.com/neuron-depolarization.html
• Image 4: http://www.mun.ca/biology/desmid/brian/BIOL2060/BIOL2060-13/CB13.html (image from Pearson Education Inc.);
http://rienstraclinic.com/newsletter/2006/February/
AP 5001 Fundamentals of Psychology Science
Week 3: Definition of Action Potential in Psychology
1

2. Action Potential
is
an “all-or-none” change in voltage that propagates
itself down the axon.
AP 5001 Fundamentals of Psychology Science
Week 3: Definition of Action Potential in Psychology
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3. Action potentials begin at the axon hillock*,
not in dendrites, not in cell bodies.
The action potential, which begins at the axon hillock, is an electrical impulse that travels down the
axon toward the terminal buttons. The action potential operates on an “all or none” principle,
meaning the axon hillock either creates an action potential or does nothing. The action potential
ends at the terminal buttons. It then stimulates them to send a chemical signal using
neurotransmitters. The terminal buttons use these chemicals to communicate with other neurons.
*The axon hillock is situated between the cell body and the axon.
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Week 3: Definition of Action Potential in Psychology
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4. The role of voltage-gated ion channels in the
action potential
AP 5001 Fundamentals of Psychology Science
Week 3: Definition of Action Potential in Psychology
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Image 1

5. Saltatory conduction
AP 5001 Fundamentals of Psychology Science
Week 3: Definition of Action Potential in Psychology
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Image 2

6. How do you get from electrical signals to
chemical signals and back again?
The action potential moves
down the axon until it
reached the synapse.
The wave of depolarization
opens voltage-activated
Ca2+ channels.
Influx of Ca2+ causes
vesicles to fuse with
presynaptic cell membrane.
Transmitter diffuses across
synaptic cleft and binds to
receptors on post-synaptic
cell.
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Image 3

7. Excitatory and inhibitory neurotransmitters
• If a transmitter depolarizes the post-synaptic neuron, it is said to be excitatory.
• If a transmitter hyperpolarizes the postsynaptic neuron, it is said to be inhibitory.
• Whether a transmitter is excitatory or inhibitory depends on its receptor.
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Week 3: Definition of Action Potential in Psychology
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8. Excitatory and inhibitory neurotransmitters
• Acetylcholine is excitatory because its receptor is a ligand-gated Na+ channel.
• GABA is inhibitory because its receptor is a ligand-gated Cl-channel.
• Other transmitters (e.g. vasopressin, dopamine) have G-protein-linked receptors.
Specific effects depend on the signal transduction pathway and cell type.
AP 5001 Fundamentals of Psychology Science Week 3: Definition of Action Potential in Psychology
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9. Some synapses form on the dendrites, cell
body, or the axon hillock.
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Image 4