neurotransmitter confusing Q

[tRNA]

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What will happen to functioning acetylcholines at the end of their neural-signal transmission?



A. They will remain binding to receptors on the postsynaptic membrane.
B. They will diffuse through the postsynaptic membrane and are ready to be reused.
C. They will be absorbed by axon bearing the presynaptic membrane and are ready to be reused.
D. They will accumulate at the synaptic cleft for a prolonged period of time.
E. They will immediately be broken down by acetylcholinesterases at the synaptic cleft.

I see E as the correct answer but why isn't C correct?????😕

both C and E are in kaplan, it says: "Neurotransmitter is removed from synapse in a variety of ways: it may be taken back up into the nerve terminal by uptake protein where it may be reused, or degraded by enzymes located in synapse eg. acetylcholinesterase"

 

[achilles2]

This can be a hard question if you don't know a fair amount about physio or pharmacology.


It depends on the neurotransmitter, for the DAT i'd just know the 2 big ones.

Nor-epi
Acetyl-Choline


Muscles are somatic and are regulated by acetyl choline, acetyl choline is secreteted then broken down by acetyl cholinesterase quickly (nerve gases inhibit acetyl cholinesterase so you build up large amounts of acetyl choline in the synapse and die a horrible death)

The choline is then uptaken and reused

Nor-epi is uptaken directly by uptake 1 after release and restored.

So C would be right if it was taking about nor-epi which is uptaken, however, acetyl Choline is quickly broken down in the synapse

Hope this helps

 

[TarheelKid24]

This is just what I think and it may not be correct...first, I don't think the neurotransmitter would be ABSORBED...it would probably attach to a membrane protein 1st. Also, if it is absorbed, it wouldn't be by the AXON but instead by the synaptic bulb...

 

[klutzy1987]

This is just what I think and it may not be correct...first, I don't think the neurotransmitter would be ABSORBED...it would probably attach to a membrane protein 1st. Also, if it is absorbed, it wouldn't be by the AXON but instead by the synaptic bulb...

I know for sure that neurotransmitters are not absorbed, they are used and recycled or degraded but never absorbed. Axon and dendrite are not absoptive at all.

 

[achilles2]

This is just what I think and it may not be correct...first, I don't think the neurotransmitter would be ABSORBED...it would probably attach to a membrane protein 1st. Also, if it is absorbed, it wouldn't be by the AXON but instead by the synaptic bulb...

for nor-epi uptake 1 is located on the nerve end that released it (axon) this is the primary uptake mechanism.

Uptake 2 is located on the cell across the synapse (target cell) generall uptake 2 is a secondary uptake in nerve conduction....


However, for acetyl choline it is broken down first in the synapse by acetyl cholinesterase.

 

[yakuza]

What will happen to functioning acetylcholines at the end of their neural-signal transmission?



A. They will remain binding to receptors on the postsynaptic membrane.
B. They will diffuse through the postsynaptic membrane and are ready to be reused.
C. They will be absorbed by axon bearing the presynaptic membrane and are ready to be reused.
D. They will accumulate at the synaptic cleft for a prolonged period of time.
E. They will immediately be broken down by acetylcholinesterases at the synaptic cleft.

I see E as the correct answer but why isn't C correct?????😕

both C and E are in kaplan, it says: "Neurotransmitter is removed from synapse in a variety of ways: it may be taken back up into the nerve terminal by uptake protein where it may be reused, or degraded by enzymes located in synapse eg. acetylcholinesterase"

No, you don't really need phys or pharmacology. It's just tricky wording. The key here is "They will be absorbed by axon bearing the presynaptic membrane and are ready to be reused"

It should be absorbed by the presynaptic membrane bearing the axon. The axon itself doesn't reabsorb anything, but the presynaptic membrane bulb does.

 

[klutzy1987]

No, you don't really need phys or pharmacology. It's just tricky wording. The key here is "They will be absorbed by axon bearing the presynaptic membrane and are ready to be reused"

It should be absorbed by the presynaptic membrane bearing the axon. The axon itself doesn't reabsorb anything, but the presynaptic membrane bulb does.

And therefore what?? The answer is wrong regardless of how it is written. Neurotransmitters are never absorbed.

 

[yakuza]

I know for sure that neurotransmitters are not absorbed, they are used and recycled or degraded but never absorbed. Axon and dendrite are not absoptive at all.

Hmm..I'm pretty sure neurotransmitters are absorbed into the nerve terminal by proteins.

 

[yakuza]

And therefore what?? The answer is wrong regardless of how it is written. Neurotransmitters are never absorbed.

lol and therefore C is wrong

Here's what kaplan says: Neurotransmitter is removed from the synapse in a variety of ways: it may be taken back up into the nerve terminal (via a protein known as an uptake carrier) where it may be reused or degraded.

 

[achilles2]

No, you don't really need phys or pharmacology. It's just tricky wording. The key here is "They will be absorbed by axon bearing the presynaptic membrane and are ready to be reused"

It should be absorbed by the presynaptic membrane bearing the axon. The axon itself doesn't reabsorb anything, but the presynaptic membrane bulb does.

??? the answer is E because you should know acetyl choline is broken down by acetylcholinesterase, thats a basic physio concept

lol and therefore C is wrong

Here's what kaplan says: Neurotransmitter is removed from the synapse in a variety of ways: it may be taken back up into the nerve terminal (via a protein known as an uptake carrier) where it may be reused or degraded.

know that this is the case for nor-epi (which is used by the sympathetic div of the nervous system)

know that acetyl choline is broken down THEN the choline is taken up and reused

and know that nerve gases target and inhibit acetyl cholinesterase which results in a build up of acetyl choline

 

[yakuza]

??? the answer is E because you should know acetyl choline is broken down by acetylcholinesterase, thats a basic physio concept


know that this is the case for nor-epi (which is used by the sympathetic div of the nervous system)

Correct, the answer is E. I was showing how C is wrong by making it true..

 

[achilles2]

Correct, the answer is E. I was showing how C is wrong by making it true..

oh sorry my mistake =)

 

[futuredent22]

I agree with Achilles2's explanation. This question is testing your understanding of acetylcholine, not your understanding of grammar. Acetylcholine is degraded to choline while it is in the synapse. Choline is then reabsorbed back into the presynaptic membrane.

Choice C is testing whether you understand that acetylcholine is degraded to choline before it is reabsorbed.

 

[yakuza]

I agree with Achilles2's explanation. This question is testing your understanding of acetylcholine, not your understanding of grammar. Acetylcholine is degraded to choline while it is in the synapse. Choline is then reabsorbed back into the presynaptic membrane.

Choice C is testing whether you understand that acetylcholine is degraded to choline before it is reabsorbed.

Yep he's right too. Acetycholine is the neurotransmitter and choline is the protein its degraded into. And nerve terminals only absorb proteins.

I had no idea what choline was until now though..

 

[tRNA]

wow the fastest respone i ever got, thanks guys I got it

 

[tRNA]

The choline is then uptaken and reused

one more question choline is uptaken back to the presynaptic terminal by what?? uptake protein ?
i checked a physio book, it also just says "uptaken" but doesn't say by what

 

[achilles2]

if you really want to know check this link

http://www.nootropics.com/cht/index.html

i'd just know its uptaken by the neuron the secreted it once its cleaved to choline


generally uptake mechanisms are sym or antiporters of ions (usually allow Na+ along with the desired uptaken product into the cell at the same time or allow K+ out of the cell and uptaken product into the cell at the same time)

its a form of active transport even tho it directly does not use ATP....instead your using the gradiant remember the Na+/K+ pump is forcing a high K+ level inside the cell and Na+ outside the cell...so allowing Na to enter or K to exit is thermodynamically favorable and you can use this energy to do work, in this case transport something AGAINST its gradiant (choline)....so your coupling a reaction, a favorable (Na+ entering or K+ leaving) with an unfavorable (substance going against its conc gradiant).

Antiport - protein the forces something out and allows something in at the same time
Symport - protein that allows two things in the same direction (in or out)

both use active transport, however, the ATP cost isn't directly observed instead generally the ion gradiant which ATP was used to generate is used to drive the reaction

hope this helps and isn't to confusing its not that easy to explain in text lol