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32 Cards in this Set
- Front
- Back
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What are the two populations of vesicles in a neuron? |
Large and small |
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What are the three known mechanisms for removing chemical messengers from the synapse? |
1) Enzymatic degradation 2) Reuptake 3) Diffusion |
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Is the binding of a transmitter to a receptor reversible? |
Yes |
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Why should transmitter be in vesicles? |
If they were free in the cytoplasm they would be vulnerable to intracellular degradative enzymes (monoamine oxidases |
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Are peptides ever in the cytosol? |
No |
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What is the subcellular fractionation technique? |
Used to isolate transmitter vesicles Separate organelles based on size, density, and shape when cell is homogenized Isolated by differential centrifugation |
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How can you break open synaptosomes (chunks of the synapse)? |
Osmotic shock in diluted water |
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How many transmitter are actually in vesicles? |
2000 |
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What is the difference between large and small vesicles? |
Large: higher concentration of transmitter Small: thought to mediate release of transmitter at active zones |
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How do transmitter deal with high concentration in vesicles? |
Bind ATP and chromogranins (soluble proteins) |
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How do vesicles concentrate small-molecule transmitters? |
pH gradient Transport powered by hydrolysis of ATP Only uncharged amine molecules are transported, inside vesicle gain charge |
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What are two important activities of synaptic vesicles? |
Move and mediate exocytosis |
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How do vesicles move to the terminals? |
Fast axonal transport from the Golgi |
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What is mobilization? |
The process by which the vesicles move from the pool to the docking sites |
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What proteins inhibit mobilization? |
Synapsins |
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What are annexins? |
Calcium-binding proteins associated with membranes, involved in mobilization |
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What happens if you put horseradish peroxidase in the synaptic cleft? |
Engulfed during endocytosis and appears in coated vesicles (clathrin-coated), eventually goes to cisternae and finally into vesicles themselves |
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Is the recycling process specific or general? |
Specific, the only membrane components recycled are those of synaptic vesicles |
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What are the three membrane retrieval pathways? |
1) Transcytosis 2) Constitutive pathway: delivered to lysosomes for degradation 3) Recycling (regulated) |
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What are the steps of exocytosis followed by endocytosis? |
1) Approach 2) Attach 3) Contact 4) Fusion 5) Opening (fission) 6) Collapse 7) Retrieval |
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How would you induce exocytosis? |
alpha-Latroxin |
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Is calcium necessary for endocytosis? |
Yes |
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What are false transmitters? |
Drugs that are sufficiently similar to the normal transmitter substance that often bind only weakly or not at all, decreasing the efficacy of transmision at specific synapses |
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Which substances are not released by exocytosis? |
Arachidonic acid and eicosanoids are membrane permeable |
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What percentage of ACh released at NMJ is due to leakage? |
90%, but it is diffuse so it is functionally ineffective |
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Why is removal of transmitters after release critical to synaptic transmission? |
If the transmitter persisted, a new signal would not get through, densensitization |
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Describe diffusion. |
Removes some fraction of all chemical messengers |
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Describe enzymatic degradation. |
Mainly in the cholinergic system, punctuates the message rapidly, allows recycling of its product |
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How would you block the degradation of transmitters in the cell? |
Monoamine oxidase inhibitors |
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Are peptides quickly removed from the synapse? |
No, proteolysis by extracellular peptidases and diffusion are likely the only mechanism of their removal |
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Describe reuptake. |
Most common Transporter molecules in nerve terminals or glia |
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Which drugs block reuptake? |
Cocaine for norepinephrine and antidepressants for serotonin |
