MEPP, EPP and acetylcholine help

[samtheman]

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Can someone explain to me what a miniature endplate potential is, what an endplate potential is, what their relationship is to acetylcholine, and any important implications with respect to their definitions (i.e why are we even learning about them)? I think I know what they are but I have yet to make any important connections between them and anything else I've learned.

Thanks

 

[engineeredout]

Whats with the massive influx of premeds lately looking for homework help? Is it because finals are coming up?

On the off chance that you aren't a premed, Single ACh vesicle release will create a MEPP. EPP is just the potential of the motor end plate. Strong enough EPP depolarization (many MEPPs simultaneously) will create an AP in teh post synaptic membrane (not the motor end plate itself).

 

[samtheman]

Whats with the massive influx of premeds lately looking for homework help? Is it because finals are coming up?

On the off chance that you aren't a premed, Single ACh vesicle release will create a MEPP. EPP is just the potential of the motor end plate. Strong enough EPP depolarization (many MEPPs simultaneously) will create an AP in teh post synaptic membrane (not the motor end plate itself).

Actually I'm a med student that did not change his status. Sorry, thanks.

 

[samtheman]

Whats with the massive influx of premeds lately looking for homework help? Is it because finals are coming up?

On the off chance that you aren't a premed, Single ACh vesicle release will create a MEPP. EPP is just the potential of the motor end plate. Strong enough EPP depolarization (many MEPPs simultaneously) will create an AP in teh post synaptic membrane (not the motor end plate itself).

What is the motor end plate? How is it different than the post-synaptic membrane. Is the motor end plate the actual muscle? BTW thanks for clearing up the first Q.

 

[ACGator09]

What is the motor end plate? How is it different than the post-synaptic membrane. Is the motor end plate the actual muscle? BTW thanks for clearing up the first Q.

from my understanding, yes. motor end plate = neuromuscular junction whereas post-synaptic membrane = neuron-neuron connection

 

[Funky]

from my understanding, yes. motor end plate = neuromuscular junction whereas post-synaptic membrane = neuron-neuron connection

I concur 👍

 

[samtheman]

Whats with the massive influx of premeds lately looking for homework help? Is it because finals are coming up?

On the off chance that you aren't a premed, Single ACh vesicle release will create a MEPP. EPP is just the potential of the motor end plate. Strong enough EPP depolarization (many MEPPs simultaneously) will create an AP in teh post synaptic membrane (not the motor end plate itself).

So you're saying the epp won't create an AP in the muscle? Won't the AP eventually get to the muscle?

Thanks

 

[samtheman]

Single ACh vesicle release will create a MEPP. EPP is just the potential of the motor end plate. Strong enough EPP depolarization (many MEPPs simultaneously) will create an AP in teh post synaptic membrane (not the motor end plate itself).

So you're saying strong enough epp won't create an AP in the muscle? Won't the AP eventually get to the muscle?

Thanks

 

[Dr Lyss]

Single ACh vesicle release will create a MEPP. EPP is just the potential of the motor end plate. Strong enough EPP depolarization (many MEPPs simultaneously) will create an AP in teh post synaptic membrane (not the motor end plate itself).

So you're saying strong enough epp won't create an AP in the muscle? Won't the AP eventually get to the muscle?

Thanks

Do you have a biochem textbook? This should be in any medical student biochem textbook. It's pretty standard and the text might be better at explaining.

The MEPPs are small depolarizations from ACh (but not enough to depolarize). If the MEPPs SUM to reach an EPP, it will depolarize the NMJ (neuro muscular junction) enough to trigger an AP in the muscle. The AP starts at the NMJ/end plate and travels down the muscle triggering an AP in the entire muscle.

An MEPP will NOT trigger an AP in the muscle. An EPP WILL trigger an AP in the muscle.

MEPP = small depolarization
EPP = depolarization past threshold to trigger an AP
NMJ = where the motor neuron and the muscle meet (where the ACh receptors are)
Pre-syn memb = the terminal of the motor neuron
Post-syn memb = the muscle (at the NMJ)

If you need more info look up neuro-muscular junction, excitation-contraction coupling, end plate potential (EPP)

 

[greatnt249]

Single ACh vesicle release will create a MEPP. EPP is just the potential of the motor end plate. Strong enough EPP depolarization (many MEPPs simultaneously) will create an AP in teh post synaptic membrane (not the motor end plate itself).

So you're saying strong enough epp won't create an AP in the muscle? Won't the AP eventually get to the muscle?

Thanks

He's saying that one vesicle of acetylcholine will cause a MEPP; usually one MEPP is not enough to depolarize the postsynaptic membrane to threshold. However, in most circumstances more than one vesicle of acetylcholine will be released upon stimulation. The resulting MEPPs from each vesicle will summate and (eventually) bring the postsynaptic membrane to threshold, resulting in an action potential.

 

[reedman]

remember that there is always a probability of vesicle release, regardless of action potential. Pre-synaptic stimulation vastly increases the probability of release.

since Ach is degraded ridiculously quickly, many vesicles have to be released to have a significant effect on the postsynaptic membrane.

check out a physiology text.

 

[illixir]

I'm pretty sure that the EPP is the equivalent of an AP in muscle. MEPP is single vesicle release as someone mentioned. In a post-synaptic neuron the terminology is actually EPSP. When you're getting into this specific of terminology about the potentials, AP is too vague I feel.

 

[greatnt249]

I'm pretty sure that the EPP is the equivalent of an AP in muscle. MEPP is single vesicle release as someone mentioned. In a post-synaptic neuron the terminology is actually EPSP. When you're getting into this specific of terminology about the potentials, AP is too vague I feel.

Except we're talking about acetylcholine in the neuromuscular junction, implying that the action results in an EPSP.🙄

If you want to quibble about terminology, the EPP causes the AP; it isn't the AP itself.

 

[illixir]

Except we're talking about acetylcholine in the neuromuscular junction, implying that the action results in an EPSP.🙄

If you want to quibble about terminology, the EPP causes the AP; it isn't the AP itself.

EPSP stands for excitatory post synaptic potential, implying a post synaptic neuron, definately not at the neuromuscular junction.

An EPP is at the neuromuscular junction.

Yea in both instances the EPSP and EPP cause the AP. The AP is all-or-none. The other two are graded.

 

[greatnt249]

EPSP stands for excitatory post synaptic potential, implying a post synaptic neuron, definately not at the neuromuscular junction.

The key descriptor in EPSP is "post-synaptic," which definitely does not imply that a neuron is on the receiving end. The muscular part of "neuromuscular" junction is definitely on the post-synaptic end of the motor neuron, and since the resultant action of acetylcholine on the nicotinic receptors in the NMJ results in depolarization (which results in MEPPs that summate to an EPP), such qualifies as an EPSP.

My point was that when a person asks a question about what the differences between MEPPs and EPPs are and how acetycholine relates to the process, it doesn't really do a lot of good to inundate with less-important details until the broader concept is understood.

 

[illixir]

Point taken. But at a neuromuscular junction, it's better to call it an EPP when there's a motor endplate.