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42 Cards in this Set

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