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42 Cards in this Set
- Front
- Back
True or false: You can't pack anymore receptors into the post-synaptic junctions.
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True
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How many subunits is an Ach receptor made out of?
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Five
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Anytime you stimulate a muscle fiber, do you get an action potential in the muscle fiber?
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Yes, everytime a nueron releases neurotransmitter there is enough of a depolarization in the muscle fiber to create a AP.
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What compound blocks nicotinic Ach receptors?
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Curare
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What compound irreversibly binds to Ach receptors and can be used to purify the receptors?
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Alpha-bungarotoxin
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Is the nicotinic Ach receptor lingand gated or voltage gated?
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Ligand gated
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What is it called when a ligand gated channel inactivates?
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Desensitization
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What is the reversal potential for a Na channel?
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+60 mV
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What is the reversal potential for a K channel?
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-90 mV
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In general what is the reversal potential for a channel?
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The potential that is near the equilibrium potential for the ion that is dominate in the channel.
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What is the reversal potential for a Ach channel?
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0 mV
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Is the Ach channel a single ion channel or a mixed cation channel?
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Mixed cation channel
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What ions mainly go through a Ach channel?
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Na, K and a tiny bit of Ca
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How fast does a Ach receptor open once it is bound by Ach?
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10 microseconds (very fast)
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How long does the Ach channel stay open?
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1 ms
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Does the Ach receptor have a high or low affinity for Ach?
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Low affinity which allows the Ach to unbind and get eaten by Achesterase. This will allow the receptor to fire again.
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Are synaptic signals regenerative?
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No they are local signals that decay in porportion to the length constant.
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Why does the local synaptic response decay as it travels?
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Ions are leaked across the membrane diminishing the signal.
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What is a quantal unit?
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It is a certain amount of NT in one vesicle that produces a certain amount of change in the post-synaptic membrane potential.
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How many molecules of Ach are in one vesicle?
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5000
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How many quantal units are needed for depolarization of the post synaptic membrane?
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200
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If one were to reduce the amount of calcium or increase the amount of magnesium at a synapse, what would happen to subsequent amount of Ach released?
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It would decrease.
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Where are vesicles concentrated?
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At the active zone
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What is it called when a vesicle first contacts the presynaptic cell membrane?
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Docking
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What process must a vesicle undergo to become ready to fuse with the cell membrane?
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Priming
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Vesicles can only be released in the presence of what?
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Calcium
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Why is there a delay between the presence of an action potential and the release a NT?
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It is due to the fact that Ca channels are slower than Na channels
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Where is the only place that calcium concentrations are high?
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At calcium microdomains...where calcium channels are open.
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What is the calcium sensor for the release of vesicles?
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Synaptotagmin
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Is diffusion alone sufficient to remove Nt from the NMJ?
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No AchE is needed as well.
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In the CNS, what is the number one way to remove NT from a synapse?
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Diffusion
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Is there a one to one synapse ratio in the CNS like in the NMJ?
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No, one cell could have up to 10,000 synapses.
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What is called when a synapse ends on a cell body? What is its function?
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Axosomatic - inhibitory
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What is called when a synapse ends on a dendrite? What is its function?
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Axonodendritic - excitatory
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What is called when a synapse ends on an axon? What is its function?
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Axoaxonic - inhibitory or excitatory
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What is called when a dendrites synapse on each other? Where can you see this?
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Dendrodendritic - in the olfactory bulb
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A central synapse is a smaller version of the what?
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NMJ
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Do central synapses have more or less active zones in comparison to the NMJ? What are the consequences of this?
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Fewer
1. Less vesicles are released 2. Failures - sometimes no NT is released 3. Don't reach AP threshold |
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Name three excitation, non-selective cation channels. What is their reversal potential?
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1. Glutamate
2. Ach 3. Seratonin 4. 0 mV |
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Name two inhibitory channels. What is their reversal potential? What is the main ion that they are permeable to?
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1. GABA
2. Glycine 3. -60 mV 4. Cl |
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What is temporal summation?
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Firing rapid AP's can bring a cell to threshold
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What is spatial summation?
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Firing from multiple neurons can bring a single neuron to AP threshold.
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