Neurotransmitters not degraded

[plzNOCarribbean]

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I read that if a neurotransmitters that are not degrade and stay in the synapse INCREASE the activity of the post-synaptic neuron?

Wouldn't it decrease the activity, because if the presynaptic neuron was trying to fire and all the neurotransmitters were in the way, they would block the incoming signal?? I donno, seems kinda counterintuitive. Anyone care to elaborate?

The question specifically was

If an acetylcholinesterase inhibitor were administered into a cholinergic synapse, what would happen to the activity of the post-synaptic neuron?

A: It would INCREASE, because acetylcholine would be degraded more slowly.

^WTF. If it is an ACh inhibitor, would it not be degraded At ALL??

 

[loveoforganic]

The action that creates the stimulus is the binding of the neurotransmitters to the receptor, not the release. So no degradation, more binding, more stimulation.

As far as your next q, inhibition isn't an all or nothing thing (usually). There will probably still be a little enzyme activity.

 

[Rayhaan]

You are partially right and partially wrong. If the transmitter is in the synapse because it can't be broken down due to some sort of inhibition of its breakdown mechanism then that signal will continue to transmit.

However, new impulses can't get their signal through as their is previous transmitter clogging up the post synaptic receptors. It is simply the old impulse that keeps going constantly. This is probably difficult to view looking at only a 1 to 1 pre to post connection.

Imagine 2 pre going onto 1 post (one is excitatory one is inhibitory). If the excitatory is sending out its signal and its transmitter isn't degraded then they sit right in front of the receptors and keep "exciting" the post synaptic neuron. Now if your brain sent a signal from the inhibitory pre synaptic neuron it CANT send that impulse as the previous transmitter is clogging up the post synaptic receptor.

 

[plzNOCarribbean]

Thanks!

 

[unhappytnt]

Yes, it would increase the activity. Think of nerve gases: They work by inhibiting acetylcholinesterase, which is the degrading enzyme for acetylcholine. As more and more acetylcholine builds up in the synapse, the more activity there will be. That's why when you kill a fly with a pesticide (they work similarly to a nerve gas), the fly will start spasming and twitching before it dies.

I hope my grisly example was good enough. 😀

 

[RUc10]

haha it seems that we are in the same point in our MCAT studying as I just finished that Bio chapter in my Examkrackers book. You got explanations already but I guess I'll add my .02 cents anyway.

Acetylcholinesterase breaks down the neurotransmitter. If something is to inhibit the function of the enzyme that breaks down the neurotransmitter that means the end result is that the neurotransmitter will not be broken down at the same rate and it will have an increased concentration. If you have increased concentration in the cleft then this will clearly cause an increase in post-synaptic membrane activity as the stimulus for the activity itself is being increased.

Btw, why was that chapter so friggin long. They definitely could have split it up into 2.