What is the difference between an EPP and EPSP?

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nebbet
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#1
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#1
Hi, I understand that this is a physiology question so I'm not sure if this is the best forum to ask about it.

I'm currently learning about synaptic transmission in the nervous system and I've just come across EPP and EPSPs. And they're treated as different things but I really don't see what the difference is between them. Correct me if I'm wrong, but aren't they both measures of membrane potential change at a neuromuscular junction where the terminal fibres of the motor neurone synapse with the muscle? In several textbooks, it refers to the this change in membrane potential in EPP due to acetylcholine release while for EPSP it is due to an increased conductance to Na/K, but I thought this was the case for EPPs as well?

Thanks for your help!
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nebbet
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#2
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#2
Bump! I would really appreciate some guidance
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Rob da Mop
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#3
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#3
End Plate Potentials (EPPs) are the depolarisations of the muscle fibre caused by the opening of ligand-gated ion channels in response to ACh release. They cause muscle contraction.

I'm not sure whether or not Excitatory Post-Synaptic Potentials can technically occur in muscles or not. They are the small depolarisation of a post-synaptic membrane in response to the opening of ligand-gated ion channels. They don't necessarily result in an action potential, but are cumulative with other EPSPs and IPSPs in the area in "deciding" whether an AP occurs.

I'll be honest, I'm a bit hazy on neuro and this is mostly me jolting my memory from wikipedia, but hopefully it's helpful.
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nebbet
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#4
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#4
(Original post by Rob da Mop)
End Plate Potentials (EPPs) are the depolarisations of the muscle fibre caused by the opening of ligand-gated ion channels in response to ACh release. They cause muscle contraction.

I'm not sure whether or not Excitatory Post-Synaptic Potentials can technically occur in muscles or not. They are the small depolarisation of a post-synaptic membrane in response to the opening of ligand-gated ion channels. They don't necessarily result in an action potential, but are cumulative with other EPSPs and IPSPs in the area in "deciding" whether an AP occurs.

I'll be honest, I'm a bit hazy on neuro and this is mostly me jolting my memory from wikipedia, but hopefully it's helpful.
So with EPPs, regardless of their strength, they will initiate muscle contraction? Ah right, the bit about EPSPs makes more sense

Ah, you're a fourth year at Cambridge...you survived pre-clinical school! I'm just a first year and there is just so much we're expected to learn
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Rob da Mop
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#5
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#5
(Original post by nebbet)
So with EPPs, regardless of their strength, they will initiate muscle contraction? Ah right, the bit about EPSPs makes more sense
Again, hazy, but I think that EPPs occur when the nerve at the NMJ fires, which releases enough ACh that the receptors on the muscle fibre are near-enough saturated. You get what are called MEPPs (miniature EPPs) which are the result of one random vesicle fusing with the pre-synaptic membrane, releasing ACh. They're not important physiologically, but with some cunning maths they let us work out how many ACh molecules are present in a vesicle.

Ah, you're a fourth year at Cambridge...you survived pre-clinical school! I'm just a first year and there is just so much we're expected to learn
I survived, just about. Don't worry, you will too, we all do in the end

You're definitely going a good way about learning the vast amount we need to learn. If you can grasp concepts like this then memorising the answers for MCQs etc is a lot easier later. Plus, if you can remember how all this nerve stuff works next year neuro will be so much easier for you! Good luck, and feel free to ask here or PM if you have any medic problems Not saying I'm a star student but I can try to help!
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nebbet
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#6
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#6
(Original post by Rob da Mop)
Again, hazy, but I think that EPPs occur when the nerve at the NMJ fires, which releases enough ACh that the receptors on the muscle fibre are near-enough saturated. You get what are called MEPPs (miniature EPPs) which are the result of one random vesicle fusing with the pre-synaptic membrane, releasing ACh. They're not important physiologically, but with some cunning maths they let us work out how many ACh molecules are present in a vesicle.
I'm feeling incredibly stupid now. I think I understand how EPPs/EPSPs work but what is the relationship between them? So EPP is when an action potential travels along a motor neurone, triggering the release of ACh at the pre-synaptic membrane, which diffuses across the synaptic cleft to bind to ACh-receptors to initiate post-synaptic depolarisation, through the entry of Na+ ions. However, with EPSP which causes a depolarisation of the post-synaptic membrane, it also increases membrane permeability to cations? Sorry, either I'm missing something big, or I dunno :/

I survived, just about. Don't worry, you will too, we all do in the end

You're definitely going a good way about learning the vast amount we need to learn. If you can grasp concepts like this then memorising the answers for MCQs etc is a lot easier later. Plus, if you can remember how all this nerve stuff works next year neuro will be so much easier for you! Good luck, and feel free to ask here or PM if you have any medic problems Not saying I'm a star student but I can try to help!
I hope you're right! The detail required for FAB is just painful and most of the time, I'm not sure if I'm doing too much or too little, due to the lack of guidance given Like you say, I'm trying to grasp the fundamental concepts...but I'm clearly struggling even with such a basic one

Cheers! Are you still in Cambridge for your clinical years?

EDIT: I re-read one of the physiology textbooks and am I right in thinking EPSP and EPP are the same thing, however EPSP is the more general term while EPP only apply at the neuromuscular junction? As they both involve nicotinic acetylcholine receptors? (I think?)
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Rob da Mop
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#7
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#7
(Original post by nebbet)
I'm feeling incredibly stupid now. I think I understand how EPPs/EPSPs work but what is the relationship between them? So EPP is when an action potential travels along a motor neurone, triggering the release of ACh at the pre-synaptic membrane, which diffuses across the synaptic cleft to bind to ACh-receptors to initiate post-synaptic depolarisation, through the entry of Na+ ions. However, with EPSP which causes a depolarisation of the post-synaptic membrane, it also increases membrane permeability to cations? Sorry, either I'm missing something big, or I dunno :/
ACCORDING TO WIKIPEDIA, TRUST YOUR HANDOUTS OVER THIS: The end plate potential is the depolarisation of the muscle fibre after being stimulated by the nerve releasing stuff blah blah blah. The end plate potential is the actual depolarisation, not the process, but as long as you're clear on that, then yes.

The EPSP is a small depolarisation of a post-synaptic membrane (normally another nerve, not a muscle). It is not necessarily sufficient for creation of an action potential. Its effects sum spatially and temporally with other EPSPs and inhibitory IPSPs to determine when an AP is fired. The EPSP is the result of an increase in the membrane permeability to cations after the ligand-gated ion channels are opened in response to neuro-transmitter. Na then enters the cell, causing the small amount of depolarisation.



I hope you're right! The detail required for FAB is just painful and most of the time, I'm not sure if I'm doing too much or too little, due to the lack of guidance given Like you say, I'm trying to grasp the fundamental concepts...but I'm clearly struggling even with such a basic one

Cheers! Are you still in Cambridge for your clinical years?
The detail required for FAB is painful and unnecessary I'm afraid The best guidance you can get for how much to be doing is to use past MCQ papers and write essay plans for past essay papers. If you can answer those then you will pass, which is the main challenge in FAB. Other than that, try to enjoy it all, don't waste dissection (my big regret from first year is the number of times I went to dissection dead tired or hung over, and not just because of how **** I felt) and learn the important concepts for clinical work - cranial nerves, arteries of the heart, the circle of Willis, blood supply of the gut etc. That's the stuff that you'll want to recall come clinical school.

I'm at Addies clinical school, yeah. Currently on placement in Huntingdon, where there is FA to do other than TSR all evening...

Edit in response to your edit: If your textbook tells you that, trust it over anything I tell you.
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nebbet
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#8
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#8
(Original post by Rob da Mop)
ACCORDING TO WIKIPEDIA, TRUST YOUR HANDOUTS OVER THIS: The end plate potential is the depolarisation of the muscle fibre after being stimulated by the nerve releasing stuff blah blah blah. The end plate potential is the actual depolarisation, not the process, but as long as you're clear on that, then yes.

The EPSP is a small depolarisation of a post-synaptic membrane (normally another nerve, not a muscle). It is not necessarily sufficient for creation of an action potential. Its effects sum spatially and temporally with other EPSPs and inhibitory IPSPs to determine when an AP is fired. The EPSP is the result of an increase in the membrane permeability to cations after the ligand-gated ion channels are opened in response to neuro-transmitter. Na then enters the cell, causing the small amount of depolarisation.
Right, I think I understand this now! You said that the EPP is the actual depolarisation, by that you mean the depolarisation of the post-synaptic membrane? Whereas in contrast to the EPSP which may not necessarily lead to a large enough depolarisation for an AP?

The detail required for FAB is painful and unnecessary I'm afraid The best guidance you can get for how much to be doing is to use past MCQ papers and write essay plans for past essay papers. If you can answer those then you will pass, which is the main challenge in FAB. Other than that, try to enjoy it all, don't waste dissection (my big regret from first year is the number of times I went to dissection dead tired or hung over, and not just because of how **** I felt) and learn the important concepts for clinical work - cranial nerves, arteries of the heart, the circle of Willis, blood supply of the gut etc. That's the stuff that you'll want to recall come clinical school.

I'm at Addies clinical school, yeah. Currently on placement in Huntingdon, where there is FA to do other than TSR all evening...

Edit in response to your edit: If your textbook tells you that, trust it over anything I tell you.
I find the fundamental FAB stuff interesting, but when Gray's lists the branches of the subclavian artery or something, then it's just tedious and rather annoying :/ Yeah, I realised how I wasted dissections in the first term. I wasn't hungover, but just never got enough sleep and I thought dissections were quite pointless. Until I got to the steeplechase, where I realised that the human body is unfortunately not colour-coded like netters xD Oh right, cheers for that advice!

Do you get to stay in accommodation attached to the hospital in Huntingdon? Can't you meet up with the other medics in Huntingdon? I actually know a fair bit about Huntingdon, having covered it in Geography A-level. From what I remember, it is basically a tiny town with pretty much zilch for student life :L You could get the train back to Cambridge?
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Rob da Mop
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#9
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#9
(Original post by nebbet)
Right, I think I understand this now! You said that the EPP is the actual depolarisation, by that you mean the depolarisation of the post-synaptic membrane? Whereas in contrast to the EPSP which may not necessarily lead to a large enough depolarisation for an AP?
Yep and yep, I think.

I find the fundamental FAB stuff interesting, but when Gray's lists the branches of the subclavian artery or something, then it's just tedious and rather annoying :/ Yeah, I realised how I wasted dissections in the first term. I wasn't hungover, but just never got enough sleep and I thought dissections were quite pointless. Until I got to the steeplechase, where I realised that the human body is unfortunately not colour-coded like netters xD Oh right, cheers for that advice!

Do you get to stay in accommodation attached to the hospital in Huntingdon? Can't you meet up with the other medics in Huntingdon? I actually know a fair bit about Huntingdon, having covered it in Geography A-level. From what I remember, it is basically a tiny town with pretty much zilch for student life :L You could get the train back to Cambridge?
Yeah, the accommodation's pretty convenient compared to some places like Peterborough, as it's actually on site, but it's a 60s atrocity that hasn't been refurbished since and only has baths, no showers. There are 16 of us here, but once you take out the people you don't know and are quite reclusive and the random number who end up back in Cambridge for the night there aren't actually that many to socialise with. Yeah, nothing to do. There aren't even any nice-looking student-priced pubs. Huntingdon and Cambridge are very close geographically but because of how British public transport works, if you want to get the train back you have to go via London. I could get the bus but £4.80 single/£6 return, 1hr 15 minute journey and ideally being in for 8:00 most days... It's not that practical! Off to the hospital now, then home, yay!
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nebbet
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#10
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#10
(Original post by Rob da Mop)
Yep and yep, I think.
great!

Yeah, the accommodation's pretty convenient compared to some places like Peterborough, as it's actually on site, but it's a 60s atrocity that hasn't been refurbished since and only has baths, no showers. There are 16 of us here, but once you take out the people you don't know and are quite reclusive and the random number who end up back in Cambridge for the night there aren't actually that many to socialise with. Yeah, nothing to do. There aren't even any nice-looking student-priced pubs. Huntingdon and Cambridge are very close geographically but because of how British public transport works, if you want to get the train back you have to go via London. I could get the bus but £4.80 single/£6 return, 1hr 15 minute journey and ideally being in for 8:00 most days... It's not that practical! Off to the hospital now, then home, yay!
Oh right. I've never really liked baths and they take too long to fill up :P ...I guess it's a way of passing the time at Huntingdon? xD I can't wait to be in 4th year now, as from the sound of things, you have loads of spare time and I really could do with some more sleep! Why don't you take up a musical instrument/do something that takes up a lot of your time? How long are you in Huntingdon for? Hope you a fun/productive day at the hospital!
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Rob da Mop
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#11
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#11
(Original post by nebbet)
great!



Oh right. I've never really liked baths and they take too long to fill up :P ...I guess it's a way of passing the time at Huntingdon? xD I can't wait to be in 4th year now, as from the sound of things, you have loads of spare time and I really could do with some more sleep! Why don't you take up a musical instrument/do something that takes up a lot of your time? How long are you in Huntingdon for? Hope you a fun/productive day at the hospital!
Third and fourth year are what you make of them, really. Third year there are people who put in a ton of effort and start publishing papers etc, and there are people who occasionally turn up to lectures, take up rowing for 3 terms and take part in 3 musicals (oops). Stage 1 (which is basically fourth year, but finishes at Easter) is about getting used to being in a hospital. It's all learning to take histories, examine and do some skills, so there's not a whole lot of book-learning for the evenings.

There are things I can do in the evenings, but I choose to spend my time cruising around the TSR biology forum!
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nebbet
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#12
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(Original post by Rob da Mop)
Third and fourth year are what you make of them, really. Third year there are people who put in a ton of effort and start publishing papers etc, and there are people who occasionally turn up to lectures, take up rowing for 3 terms and take part in 3 musicals (oops). Stage 1 (which is basically fourth year, but finishes at Easter) is about getting used to being in a hospital. It's all learning to take histories, examine and do some skills, so there's not a whole lot of book-learning for the evenings.

There are things I can do in the evenings, but I choose to spend my time cruising around the TSR biology forum!
It sounds like some people just take advantage of the social-side of Cambridge to the max! That sure does sound fun though (bar the taking part in musicals...acting is certainly not my forte!). One final thing, do most people get their first-choice clinical school? As there are loads of rumours and statistics passed around, e.g. you need a minimum of 2:i/preferably a 1 in both years to stay in Cambridge?

I'm sure I speak on behalf of many others on this forums- thanks for your help!
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Rob da Mop
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#13
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#13
(Original post by nebbet)
It sounds like some people just take advantage of the social-side of Cambridge to the max! That sure does sound fun though (bar the taking part in musicals...acting is certainly not my forte!). One final thing, do most people get their first-choice clinical school? As there are loads of rumours and statistics passed around, e.g. you need a minimum of 2:i/preferably a 1 in both years to stay in Cambridge?

I'm sure I speak on behalf of many others on this forums- thanks for your help!
You definitely don't need that. Getting good grades helps, but the application form has 3 white-box questions about ECs, academic things and something else I can't remember (possibly something generic like why Cambridge?) and there is then an interview. There are places at the moment for about 60% of students at Cambridge (they're trying to increase this, but I'm not sure what the timescale is), but a fair few people want to go to London, so your chances of getting into Cambridge are significantly better than 60%. I know few people who got rejected from Cambridge and they were all fairly happy with imperial/kings as their second choices.
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