View source for Talk:Chemical synapse

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==Older edits==
That's as maybe, but I want also to add that there are different kinds of synapse. Most are chemical in nature, such as are already described. However, there is evidence for some very fast acting synapses which are electrical. These are reported to have been discovered in fish. Assuming that this has not been discredited, it would be worth having a section on electrical synapses.
[[User:David Martland|David Martland]] 00:06, 16 Jan 2004 (UTC)

[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11389476&dopt=Abstract Electrical synapses between GABA-releasing interneurons. Nat Rev Neurosci. 2001 Jun; 2(6): 425-33. Galarreta M, Hestrin S.]

*''Although gap junctions were first demonstrated in the mammalian brain about 30 years ago, the distribution and role of electrical synapses have remained elusive. A series of recent reports has demonstrated that inhibitory interneurons in the cerebral cortex, thalamus, striatum and cerebellum are extensively interconnected by electrical synapses. Investigators have used paired recordings to reveal directly the presence of electrical synapses among identified cell types. These studies indicate that electrical coupling is a fundamental feature of local inhibitory circuits and suggest that electrical synapses define functionally diverse networks of GABA-releasing interneurons. Here, we discuss these results, their possible functional significance and the insights into neuronal circuit organization that have emerged from them.''


Yes, I think electrical synapses deserve a section, if not some systemic changes to admit to the recently broadened concept of synapse. Gap junctions didn't used to be considered synapses, but evidently now they are. [[User:168...|168...]] 16:31, 16 Jan 2004 (UTC)

==Synapses and circuits==
"Synapses define the circuits in which the [[neuron]]s of the central nervous system interconnect."

was changed to "Synapses are circuits...." 

Synapses are functional contacts for communication between nearby cells. Most synapses are between adjacent neurons, but some synapses are from neurons onto other cell types such as muscle cells. Synapses are of two types: electrical synapses and chemical synapses. Electrical synapses provide cytoplasmic connections between adjacent cells where ions can carry charges from one neuron to another. Chemical synapses provide cell-to-cell communication that is mediated by neurotransmitters. A neurotransmitter is a chemical that is released from one neuron, moves to a nearby neuron, and acts to modulate the physiology of the target cell. Neurotransmitters often work by binding to receptor proteins on the surface of cells. However, some neurotransmitters pass through cell membranes and directly influence target proteins inside their target neurons. Structurally, synapses are usually regions of close contact between adjacent neurons. Most neurotransmitters are packaged into vesicles at the presynaptic side of synapses. Most neurotransmitter receptors are concentrated in post-synaptic densities on the post-synaptic side of synapses. When activated by neurotransmitters, neurotransmitter receptors typically change ion flow across the surface membrane of postsynaptic neurons. Neurotransmitter receptors can have other effects such as regulation of gene transcription and the regulation of synaptic plasticity (changes in the functional and structural properties of the synapses themselves). The interconnected networks of neuronal cell bodies, axons, synapses and dendrites can be thought of as circuits that carry signals using a mixture of chemical synapses, electrical synapses, action potential propagation, and signals in the form of graded potential changes at cell surface membranes. [[User:JWSchmidt|JWSchmidt]] 23:41, 29 Mar 2004 (UTC)

This may be syntax curmudgeonery, but I think the original was more acurate.  As you said, "The interconnected networks of neuronal cell bodies, axons, synapses and dendrites can be thought of as circuits" but that doesn't make synapses circuits themselves, as the sentence implies, only components of them.  This stuck out to me immediately upon reading the article.  I'm changing it to "synapses form the circuits" because that seems to say everything that's needed. [[User:24.0.213.140|24.0.213.140]] 20:28, 29 Aug 2004 (UTC)

==Synaptic Strength==
*"Synaptic strength is the amount of current, or more strictly the change in transmembrane potential of the synapse."
*"One regulatory trigger of synaptic strength involves the simple coincidence sensory stimuli and action potentials in the synaptically linked cells."

1) I'm not sure why these two "sentences" seem to have a charmed life on the synapse page. They both should be fixed. 

2) If you look in a neuroscience textbook ([http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?call=bv.View..ShowTOC&rid=neurosci.TOC&depth=2 example]) you will find discussion of synaptic strength mostly in the context of synaptic plasticity. I tried adding some basic information about synaptic plasticity. It was removed, leaving these two (above) problem sentences. 

In summary, the "Synaptic Strength" section needs help but I'm not sure I should make any more effort to help it. [[User:JWSchmidt|JWSchmidt]] 00:47, 30 Mar 2004 (UTC)

:I think all efforts should be made to ensure that this page has nothing to do with plasticity. We are currently trying to update the [[Synaptic plasticity|plasticity ]]page, but I have been running around on the [[AMPAR]] page and [[NMDAR]] page trying to fix errors with respect to plasticity there. The only thing that you might want to mention is the p,N,q parameters (probability of release, number of neurotransmitters, and sensitivity of receptors) which characterize the 'strength' of a synapse. [[User:Paskari|Paskari]] ([[User talk:Paskari|talk]]) 17:49, 23 July 2008 (UTC)

==Lack of references==
Hi this article no longer meets the [[Wikipedia:What is a featured article|criteria]] for a featured article because it does not [[Wikipedia:Cite sources|cite its sources]].  Please help fix this so that all featured articles can meet the same standards. Best would be the most trusted resources in the field being added, some print resources especially, but also online references are better than none.  Those sources would likely help with good material to further improve the article anyway. - [[User:Taxman|Taxman]] 23:00, Oct 26, 2004 (UTC)

:I added two of the most common neuroscience textbooks (Kandel and Bear) as references. If anyone who contributed to this article had more specific references in mind, please add them. [[User:Sayeth|Sayeth]] 17:43, Nov 1, 2004 (UTC)
::Would you say you are very confident that the material in those books agrees with what is here?  Otherwise that is potentially dishonest to list them as references. - [[User:Taxman|Taxman]] 19:11, Nov 1, 2004 (UTC)
:::Yes, both books state what is now the established dogma of synaptic transmission and [[action potential]] propagation, which is repeated in the wikipedia articles.  In all likelihood, at least some of the authors of these articles used the Kandel or Brown textbooks as their source, since these are the primary textbooks for graduate and undergraduate courses in neuroscience. If the articles delved into more the esoteric mechanics of these neural functions, then there might be some conflict with the books, but as it stands now, they agree. [[User:Sayeth|Sayeth]] 17:03, Nov 2, 2004 (UTC)
::::Ok, sounds good to me.  Thanks for helping and being willing to explain. - [[User:Taxman|Taxman]] 18:35, Nov 2, 2004 (UTC)

I used Kandel & Schwartz in graduate school and think it's a perfect reference.

== Dimension of a synapse ? ==

Which is the average size of a synapse ? It is probably smaller than a micron since the neurons size is between 5 and 150 microns, but I would like to know their real size.

: It's hard to tell exactly what dimensions you're speaking of, but I'd bet you're asking about the distance between pre- and postsynaptic neurons. The gap is called the [[synaptic cleft]] and it is typically 20-30 [[nanometer|nm]] across. Here's a [http://synapses.mcg.edu/anatomy/chemical/cleft.htm nice visual]. --[[User:Diberri|David Iberri]] | [[User talk:Diberri|Talk]] 22:09, Apr 13, 2005 (UTC)

:: What is the typical cross section area of a synaptic cleft? The volume?
::--[[User:Erl|Erland Lewin]] 10:25, 3 August 2006 (UTC)

== New diagrams ==

Hello, just wanted to tell you that I have drawn a few diagrams related to synapse. Please check the french version of the article [[:fr:Synapse]]. The pictures are on Commons.  [[User:Dake|Dake]] 13:13, 2 September 2005 (UTC)

:*I have a few comments about these diagrams: 1) The picture of a synapse is nice, but I think the one on the English article already is more complete and maybe more accurate and it is already annnotated directly, so I wouldn't suggest changing it. 2) The images of a neuromuscular junction are nice and I would suggest you put them in the NMJ article. However I did notice that the second image has no repetors on the postsynaptic surface! 3) The synapse article does not have a picture of an electrical synapse, and your looks nice, one thing I'm not sure about though is whether presynaptic Ca++ channels are important for electrical transmission and if not why are they in the diagram. 4) Finally, there are separate articles for action potentials and EPSPs. Also, why is the EPSP waveform so strange looking.  I think the images are of very good quality, but perhaps not as complete or accurate as they may be.  I'd normally be happy to comment on the French version of synapse to look for completeness/accuracy, but alas I don't speak French well enough to do so.  It  looks very thorough however.  Cheers, [[User:Nrets|Nrets]] 14:00, 2 September 2005 (UTC)


== Include Number of Synapses in Human Brain ==

A common question is how many synapses are in the human brain. I suggest mentioning current estimates. It's 1000 trillion for a one year old baby, declining to about 500 trillion for an adolescent. Recent data indicates this number stays constant into adulthood, unlike earlier estimates stating it declined to 100 trillion. (Shore, Rima, Rethinking the Brain: New Insights into Early Development, Families and Work Institute, 1997) [[User:Joema|Joema]] 17:18, 21 December 2005 (UTC)

I think 1 quadrillion is about right - no one has counted them all. For the cerebral cortex the density is around 1 billion per cubic millimeter. Frankly the best one can hope is right order of magnitude, and 1 quadrillion is easy to remember (though difficult to visualize: I tell my students think 1 cent in the entire US economy).  <small><span class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Paulhummerman|Paulhummerman]] ([[User talk:Paulhummerman|talk]] • [[Special:Contributions/Paulhummerman|contribs]]) 03:12, 15 May 2010 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->

*I think that's a great idea, maybe it might fit better (or also) in the brain article. However, I'm a bit dubious about the source of these estimates. Would you be able to identify the primary sources mentioned in the book you quote, or perhaps a more established secondary source would do (such as a major textbook in the field). [[User:Nrets|Nrets]] 21:48, 21 December 2005 (UTC)

Well, this is harder than I thought. I've done many internet and library database searches, and there's apparently no uniform consensus. Evidently there's general agreement a three-year-old child has 1,000 trillion synapses. However estimates vary on number of adult synapses from 100 trillion to 500 trillion. Below are a few more authoritative references. The statement about 7,000 synapses per neuron, one trillion synapses per cc seems authoritative. However at an average of 1241 cc for the male brain, that equates to 124 trillion synapses.

Because of this I'd recommend saying something like: "The human brain has a gigantic number of synapses. Each of 100 billion neurons has on average 7,000 synaptic connections to other neurons. Most authorities estimate total number of synapses at 1,000 trillion for a three-year-old child. This number declines and with age, stabilizing by adulthood. Estimates vary for an adult from 100 to 500 trillion synapses. [[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15985565&query_hl=1&itool=pubmed_docsum]]

That way you provide useful information without stating more than references indicate. Because of the wide Wikipedia readership, just stating this might engender more authoritative expert commentary. [[User:Joema|Joema]] 18:37, 22 December 2005 (UTC)

References:

Biophysics of Computation. Information Processing in Single Neurons, C. Koch, New York: Oxford Univ. Press, 1999, page 87).

Above says total synapses in the cerebral cortex are 240 trillion


COGNITIVE NEUROSCIENCE AND CLASS ROOM DESIGN, John P. Eberhard, Ilya Monosov
(PDF): [http://www.architecture-mind.com/COGNITIVE%20NEUROSCIENCE%20AND%20CLASS%20ROOM%20DESIGN.pdf]

Above states 1000 trillion synapses at age 3, and 500 trillion from age 15 onward


FUNDAMENTALS OF EEG MEASUREMENT
M. Teplan
Institute of Measurement Science, Slovak Academy of Sciences, Dúbravská cesta 9,
841 04 Bratislava, Slovakia

"Adults have about 500 trillion (5.10E14) synapses"


Do we have brain to spare?
David A. Drachman, MD
From the Department of Neurology, University of Massachusetts Medical School, Worcester, MA. 

[http://www.neurology.org/cgi/content/full/64/12/2004?ijkey=1ba4dce663a9f89917b1f4dbe5d52b585cf5e890&keytype2=tf_ipsecsha]

"Neurons have 7,000 synaptic connections each. The cerebral cortex has about 0.15 quadrillion synapses—or about a trillion synapses per cubic centimeter of cortex."


*Your sentence sounds good, I copied into the [[Neuron]] entry, but I couldn't figure out where to put it in the [[Synapse]] article.  [[User:Nrets|Nrets]] 19:34, 22 December 2005 (UTC)


**Personally I think it's such an obvious question, it wouldn't be out of place in the first section. You could abbreviate it something like "Young children can have 1,000 trillion synapses. This number declines and with age, stabilizing by adulthood. Estimates for an adult vary from 100 to 500 trillion synapses." [[User:Joema|Joema]] 20:25, 22 December 2005 (UTC)

*Sounds reasonable. I have no complaints if you add that there. [[User:Nrets|Nrets]] 20:30, 22 December 2005 (UTC)

**OK I made my best guess at location and wording. Make any changes you see fit. [[User:Joema|Joema]] 00:08, 23 December 2005 (UTC)


Disagree, I have removed it. Why is it included in the [[WP:LEAD]]? It makes no sense 
whatsoever. I have removed the numbers, per [[WP:BOLD]]. --[[User:Parker007|Parker007]] 06:28, 7 March 2007 (UTC)
Can you help with this one?

I am researching 'A Theory Of Mind' which has, as one of its props, a speculation that a 'bit' of memory resides in the synapse.  I am led to this belief because the count of total number of sensory inputs which the brain could receive in a normal life-span is roughly equal to the estimated number of synapses which exist. If so, it is logical to assume that a synapse might be armed with a 'bit' of memory at the time of the original experience.  It is also possible that the number of vesicles provided (pre-synapse) might correlate with the degree of emotional pain/pleasure felt at that precise moment.  If this assumption is correct then the number of vesicles present in the axon should vary in concord with the strength of the original emotion.  The effect would be to mirror that same emotion at recall.

Is there any clinical evidence to support/refute these assumptions?

Regards, 
Don Nicol
9 Jun 2007

*You're looking for [[Long-term potentiation]]. --[[User:Dpryan|Dpryan]] 19:27, 9 June 2007 (UTC)

== Featured article removal candidate ==

As I claim on [[WP:FARC]], this article no longer fulfils the criteria for being a Featured Article. Specifically, it does not cover the subject in adequate depth and breadth by today's standards, and lacks in references; specifically, it needs inline references. I believe these are serious shortcomings and that the article will be better served by being demoted rather than half-hearted attempts at fixing it just so it can barely scrape acceptance as an FA. It would be nice to be convinced that the article can be swiftly and impressively fixed, but will defend my proposal to demote in the absence of any such activity.

Regards,

[[User:Samsara|{{{2|Samsara}}}]] ([[User talk:Samsara|talk]] • [[Special:Contributions/Samsara|contribs]]) 19:58, 21 May 2006 (UTC)

*'''Keep''', most, if not all of the factual information is found in the references cited and represent years of neurophysiology research, adding inline refs for every fact in the article would make it hugely unweildy. Recently I expanded, corrected and reorganized the entire article, adding new diagrams and such and I think it definitely still meets the FA quality. Since this is such a big topic I think that it is appropriate to keep many of the sub areas as separate articles (ie. [[postsynaptic potential]], [[neuromuscular junction]], etc.) thus it explains why this article is not so long. I've been continuously checking the article to make sure everything is up-to-date. [[User:Nrets|Nrets]] 00:48, 22 May 2006 (UTC)

== Chemical vs. electrical ==

Chemical synapse redirects here. [[Electrical synapse]] does not. Any thoughts? - [[User:Samsara|{{{2|Samsara}}}]] ([[User talk:Samsara|talk]] • [[Special:Contributions/Samsara|contribs]]) 18:01, 24 May 2006 (UTC)

:This article basically describes a chemical synapse which is the "prototypical" synapse, electrical synapse has its own article. We could merge these? [[User:Nrets|Nrets]] 18:57, 24 May 2006 (UTC)

::It would be cumbersome to the reader to have chemical, electrical, and immunological synapses all on the same page. Instead, each topic should have its own article. As "synapse" most often refers to the chemical sort, a redirect from [[Synapse]] to [[Chemical synapse]] would be in order. --[[User:Diberri|David Iberri]] ([[User talk:Diberri|talk]]) 03:48, 4 June 2006 (UTC)

:::I've moved the page from [[synapse]] to [[chemical synapse]] per above. Now [[chemical synapse|chemical]], [[Electrical synapse|electrical]], and [[immunological synapse]]s have their own articles. --[[User:Diberri|David Iberri]] ([[User talk:Diberri|talk]]) 17:01, 21 June 2006 (UTC)

== Merge Synaptic Bouton ==

Synaptic Bouton is more or less orphaned, a stub, and really a part of a chemical synapse.  I say we add what little content it has to this article and redirect synaptic bouton here. --[[User:Selket|Selket]] 07:54, 1 February 2007 (UTC)

:Sound like a good plan. [[User:Nrets|<span style="color:#99CC66;"><u>Nrets</u></span>]] 17:56, 2 February 2007 (UTC)

== Removal of sentences from the Anatomy and physiology  ==
''Second Sentence''
*The [[biological membrane]] of the two cells side each other across a slender gap, the narrowness of which enables signalling [[neurotransmitter]]s to pass rapidly from one cell to the other by [[diffusion]]. This gap, which is about 20 nm wide, is known as the '''synaptic cleft'''. 

*Which 2 cells? --[[User:Parker007|Parker007]] 06:20, 7 March 2007 (UTC)
**The two cells referred to in the preceding sentence. --[[User:Diberri|David Iberri]] ([[User talk:Diberri|talk]]) 16:02, 10 April 2007 (UTC)

''Third sentence''
*Such synapses are asymmetric both in structure and in how they operate. 

*Which such syapses? --[[User:Parker007|Parker007]] 06:23, 7 March 2007 (UTC)
**"Such" has apparently been removed for clarity. --[[User:Diberri|David Iberri]] ([[User talk:Diberri|talk]]) 16:02, 10 April 2007 (UTC)

==The synapses-state description of he total organism==
Synapses are not all biochemically identical. The way they increase their effiency upon activation, and the rate of they regression upon inactivation undoubtedly is different from one synpse to another. At any moment each synapse will be in a certain state of efficiency. The mental state of the organism is then given by the momentary state of efficiency of each of the synapses. 

Being alive then means that the organism is in continual change in witch at any moment a certain part of the neurons and the synapses transmit impulses, which are distributed into the network of neurons according to the current state of efficiency of the synapses, each synaptic eficiency in its turn being changed by the transmission intensity it is subjected to, typically increasing when the intensity is high, decreasing when it is low.
<small>—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Mightunit|Mightunit]] ([[User talk:Mightunit|talk]] • [[Special:Contributions/Mightunit|contribs]]) 12:11, August 24, 2007 (UTC)</small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->

==Move==
Would it not be better just to have this at [[synapse]] instead of having a more specific name? The former just redirects here, so why not move it to the simpler name as has been done with other articles, e.g. [[biological reproduction]]. [[User:Richard001|Richard001]] 01:53, 25 August 2007 (UTC)
:This was discussed before (check the history for this page, I think). The reason is that there are [[immunological synapse]]s, [[electrical synapse]]s, and [[chemical synapse]]s, all of which are a type of synapse. [[Synapse]] redirects to [[Chemical synapse]] because when unqualified, "synapse" most often refers to the chemical variety. --[[User:Diberri|David Iberri]] ([[User talk:Diberri|talk]]) 15:49, 26 August 2007 (UTC)

==The Anatomy Section: Huh?==
"At an archetypal chemical synapse, such as those found at dendritic spines, a mushroom-shaped bud projects from each of two cells and the caps of these buds press flat against one another. At this interface, the membranes of the two cells flank each other across a slender gap, the narrowness of which enables signaling molecules known as neurotransmitters to pass rapidly from one cell to the other by diffusion. This gap, which is about 20 nm wide, is known as the synaptic cleft."

So do the caps really press flat against one another, or is there actually a gap between them? If there is a gap, how is it that the two really press flat against one another? If there is actually a gap, would it be accurate to say, then, that there is only the ''appearance'' of the direct physical contact via the membranes that's also suggested? 
I don't quite understand.
Is it that the membranes are pressed against one another, but contain a gap (or the synaptic cleft) within, or inside that zone of contact? The idea that one gets from the synapse illustration (for example, http://en.wikipedia.org/wiki/Image:SynapseIllustration2.svg and http://en.wikipedia.org/wiki/Image:Complete_neuron_cell_diagram.svg) is that there is no actual membrane contact, only a very close proximity that, nonetheless, precisely falls short of the two cells pressing against one another due to the synaptic cleft.
I admit that I ''am'' missing something, but perhaps this is because of the ambiguity inherent in the description supplied. Could someone please clarify this point, on the article page or even here?

-[[Special:Contributions/72.68.221.206|72.68.221.206]] ([[User talk:72.68.221.206|talk]]) 20:39, 18 November 2007 (UTC)

:I've changed that ambiguity you mentioned. The projections don't physically touch each other, which results in the creation of the cleft. Hopefully this is clearer now. --[[User:Dpryan|Dpryan]] ([[User talk:Dpryan|talk]]) 04:24, 19 November 2007 (UTC)

::Why exactly do the two synapses not touch eachother, but stay at a casual distance of 20 nm? Is it because of the 'cell adhesion proteins'? [[User:Paskari|Paskari]] ([[User talk:Paskari|talk]]) 17:55, 23 July 2008 (UTC)

== Question about the alignment of the synapses ==

I didn´t spot it in the article so my question is: Why does the presynaptic cell align with the postsynaptic cell in such an exact way? 

Kinda hard to find the correct words for it, so lets say we have a regenerating neuron that´s currently in the progress of remaking the connection with another cell after injury: 
How do they connect to each other in the first place? What makes the presynaptic terminal "connect"? [[User:Fernando Hulio|Fernando Hulio]] ([[User talk:Fernando Hulio|talk]]) 14:08, 8 July 2008 (UTC)
:I would suggest starting by looking at [[synaptogenesis]].  Perhaps there should be a link to that page somewhere in this one. [[User:Xargque|Xargque]] ([[User talk:Xargque|talk]]) 16:21, 8 July 2008 (UTC)

== Synaptic Duration ==
I find computer scientists, when creating neural network simulators, create synapses with three attributes: a strength, a synaptic delay, and a synaptic duration. The strength value is self explanatory (albeit over simplified). The synaptic delay represents the axonal delay+delay from end of axon to axon buttons. The synaptic duration is the one that strikes me as a bit odd. I know that exocytosis is extremely rapid (<200 microseconds), and I know that the strength of a presynaptic synapse is characterized by the probability of vesicle release (p) and the number of release sites (N), but is there also a temporal component to synaptic strength? Do stronger synapses release their neurotransmitters for a longer period of time? I highly doubt this. [[User:Paskari|Paskari]] ([[User talk:Paskari|talk]]) 18:01, 23 July 2008 (UTC)

:When you start looking at network scale models you'll find that the math doesn't necessarily map perfectly onto the underlying individual neurons (e.g. you might model the neuron not as a series of compartments with conductances but as a [[black box]]). --[[User:Dpryan|Dpryan]] ([[User talk:Dpryan|talk]]) 19:41, 28 July 2008 (UTC)
Yes I realize that, and I don't support having a single neuron equation for an artificial neuron. But that single equation models the axon hillock, and the entire somatic and dendritic membrane is ignored. But with synaptic duration, it seems as if it never existed, and computer programmers devised it. [[User:Paskari|Paskari]] ([[User talk:Paskari|talk]]) 15:16, 31 July 2008 (UTC)
:The transmitter stays bound to the postsynaptic receptors for some amount of time (5 to 500 ms).  Plus, once the membrane has been depolarized, it has to relax back to resting potential with a certain time constant (which can also be on the order of tens of milliseconds).  Is that what you're wondering about? [[User:Xargque|Xargque]] ([[User talk:Xargque|talk]]) 17:22, 31 July 2008 (UTC)
I suppose that does answer my question, so once an axon terminal button releases its neurotransmitters, the spines open up their channels for some ''synaptic duration''. So if you were running a simulation at a one millisecond precision, once the channels are opened, you would provide an input to the neuron model for a duration which could be longer than a single cycle (1 ms). Thanks [[User:Paskari|Paskari]] ([[User talk:Paskari|talk]]) 18:14, 2 August 2008 (UTC)

== Number of synapses ==

There was a contradiction with the article [[Neuron]] in the numbers for the estimates of the number of synapses in the adult human brain. In the talk section above, [[#Include Number of Synapses in Human Brain]] and in the first edit concerning this way back in 23 December 2005 [http://en.wikipedia.org/w/index.php?title=Chemical_synapse&diff=32423360&oldid=32392480], this was given as 100-500 trillion. Then on 16 November 2006, someone added it in scientific notation, but got the number wrong, putting 15 instead of 14 [http://en.wikipedia.org/w/index.php?title=Chemical_synapse&diff=next&oldid=88041766] and the next day, the numbers were changed from 100 to 500 trillion to 1,000 to 5,000 trillion. I've changed the numbers back to the way they were, making them the same as those given in [[Neuron]]. --[[Special:Contributions/121.45.173.99|121.45.173.99]] ([[User talk:121.45.173.99|talk]]) 10:23, 3 August 2008 (UTC)

== Homotropic/Heterotropic vs Homosynaptic/Heterosynaptic ==

I have never heard of the term homotropic modulation or heterotropic modulation applied to synapses.  It is more common to refer to homosynaptic or heterosynaptic plasticity.  There were errors in the content of that section as well.  I'm not aware of any example where the size of vesicles is affected by the neuron's own activity or other neurons' activity.--[[User:Pkatz|Pkatz]] ([[User talk:Pkatz|talk]]) 15:08, 30 August 2008 (UTC)

== Removing refimprove tag ==

I have boldy removed the ''refimprove'' tag from the article.  Synapses are the central topic in neuroscience, and are discussed thoroughly in every basic neuroscience textbook, so there is no problem in verifying most of the assertions in this article.  If there are specific assertions that you think require verification, please feel free to mark them with a "fact" tag. [[User:Looie496|Looie496]] ([[User talk:Looie496|talk]]) 17:15, 15 September 2008 (UTC)

== Volume transmission ==

Can we please settle this on the talk page rather than edit warring?  It is definitely true that volume transmission is an important concept that ought to be mentioned in this article -- in fact, Wikipedia ought to have an article about it; currently [[Volume transmission]] redirects to a section of [[Brain]].  What isn't true is that it is a new concept -- people have been studying this for decades, and there is a massive literature on it.  (And I'm not talking about electrical synapses, I'm talking about chemical transmitters acting extra-synaptically.)  Let's see, please, if we can find a good review of this topic and add a mention at an appropriate place in the article. [[User:Looie496|Looie496]] ([[User talk:Looie496|talk]]) 18:06, 24 November 2009 (UTC)

:I tried inserting a comment about volume transmission a number of times and have been frustrated by it being edited out repeatedly. I cited two references in my edit dated from 24 November 2009 at 17:16. Yes, volume transmission has been been well-studied, and nobody suggested it was a new concept. What is new, is the Naure paper I cited (Olah et al., Nature 2009), which was the first to show that individual neurogliaform cells do not require synapses to produce a response (in this case GABA-mediated inhibition). If you have a subscription to Nature, please check it out here: http://www.nature.com/nature/journal/v461/n7268/full/nature08503.html. The paper was published on October 29th, 2009 so will not be in any review papers for a while.  
:--[[User:Joconnol|Joconnol]] ([[User talk:Joconnol|talk]]) 19:29, 24 November 2009 (UTC)
::Adding the material about volume transmission is very appropriate, as is the Nature reference. The problem, first, was that the edit was initially written in a way that sounded like it was about electrical synapses, not volume transmission, and second, that the source from the "what your teacher didn't know" website was not encyclopedic. Writing it as being clearly about volume transmission, and referencing it to Nature, would be fine. I'll be happy to help copyedit it if you do that. Thanks. --[[User:Tryptofish|Tryptofish]] ([[User talk:Tryptofish|talk]]) 19:46, 24 November 2009 (UTC)

::I'll reiterate Tryptofish's comment, it's certainly an appropriate addition provided it's worded in a way that it's immediately apparent what's being talked about. I think that was much of the problem. The topic should also have its own article, if someone has a chance. --[[User:Dpryan|Dpryan]] ([[User talk:Dpryan|talk]]) 06:09, 25 November 2009 (UTC)


My initial edit referred to signaling in the absence of synapses - how this sounded like it was about electrical synapses is beyond me. I take your point about referencing, and included the Nature ref in my second edit. I retained the blog reference, as I assumed this would be more penetrable to the layperson. 
If you agree that volume transmission should be covered in this wiki, please take the time to edit the text or contribute an alternative rather than edit warring, as Looie496 has correctly pointed out. Tryptofish, I have pasted the text of my most recently deleted edit below - perhaps you or someone else can take a stab at rewriting, rewording, or copyediting. As I said before, it is extremely frustrating to have legitimate attempts at improving an entry deleted without any effort to consider the content. 

New section heading title: 
Signaling without synapses

Section text: 
Until recently, synaptic transmission had been considered the exclusive mechanism by which neurons communicate. However, this is no longer thought to be the case[16]. Oláh et al. (2009)[17] found that a type of neurons called neurogliaforms can communicate using a mechanism called volume transmission, where neurochemicals diffuse in a cloud through the extracellular fluid. This occurs even when no synapses are present. The group found that approximately 78% of neurogliaforms do not form classical synapses. This is the first example of neurons communicating where synapses are not present.

References: 
Ref 16: "Your Teacher was Wrong!". Dolan DNA Learning Center. http://blogs.dnalc.org/g2conline/2009/11/12/your-teacher-was-wrong/. Retrieved 2009-11-12. 
Ref 17: Oláh S, Füle M, Komlósi G, Varga C, Báldi R, Barzó P, Tamás G. (2009). "Regulation of cortical microcircuits by unitary GABA-mediated volume transmission.". Nature 461 (7628): 1278-1281. {{PMID|19865171}}. http://www.ncbi.nlm.nih.gov/sites/entrez/19865171.  <small><span class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Joconnol|Joconnol]] ([[User talk:Joconnol|talk]] • [[Special:Contributions/Joconnol|contribs]]) 14:43, 25 November 2009 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->
:Please understand that nothing here was a personal criticism of you (although I think Looie's advice about not edit warring was directed at you). It looked to multiple editors like the edit was part of the section on electrical synapses. Anyway, thank you for working up the edit on this talk page. I will now edit it further, and incorporate it into the article. Please do not be discouraged about editing at Wikipedia. You have done us all a service by making us notice that volume transmission needs to be covered. --[[User:Tryptofish|Tryptofish]] ([[User talk:Tryptofish|talk]]) 16:21, 25 November 2009 (UTC)

::Way to condescend! Can someone else please fix the new volume transmission edit? The current version is a bad re-write of my initial text on this talk page. I would do it myself but suspect any such attempt will be rolled back. --[[Special:Contributions/143.48.90.133|143.48.90.133]] ([[User talk:143.48.90.133|talk]]) 18:36, 25 November 2009 (UTC)
:::Sorry I wasted my time. No, I was not condescending, and, no, you are not such a good writer. --[[User:Tryptofish|Tryptofish]] ([[User talk:Tryptofish|talk]]) 19:57, 25 November 2009 (UTC)

:::Can you specify what is bad about it? The only change I could suggest is to insert the word "all" and say "...had been considered the primary mechanism by which all neurons communicate." Of course, I'm not entirely sure that this change would be correct (there may be counter examples others are aware of), so I'm not going to edit that in myself. --[[User:Dpryan|Dpryan]] ([[User talk:Dpryan|talk]]) 20:37, 25 November 2009 (UTC)

::::I've added some background, and corrected a couple of things on the basis of the Nature article.  Probably still needs work. [[User:Looie496|Looie496]] ([[User talk:Looie496|talk]]) 22:40, 25 November 2009 (UTC)
:::::Thanks. That's a big improvement over what I did. --[[User:Tryptofish|Tryptofish]] ([[User talk:Tryptofish|talk]]) 14:52, 26 November 2009 (UTC)

== Symmetric and asymmetric synapses ==
I've added a quick paragraph about symmetry of synapses in the structure section. I've not sourced it yet, there's some stuff here http://thebrain.mcgill.ca/flash/capsules/pdf_articles/synapses.pdf plus some more content if the section gets expanded, including the history of the teriminology. There's already a reference to the chemical synapse being "asymmetric in structure and function" because the signalling is one way (although you might argue that autoreceptors mean that the process isn't exclusively one directional). However, as far as I can tell, this isn't the same as the structural symmetry of the synaptic membranes.[[User:Keepstherainoff|Keepstherainoff]] ([[User talk:Keepstherainoff|talk]]) 14:06, 20 July 2010 (UTC)

== Video clips ==

[[File:Synapse.theora.ogv|right|250px]]In cooperation with user Looie I have created a 60 seconds video clip on the basic processes of the chemical synapse.  This is a 13MB file.  Smaller resolutions (equals smaller size) is possible but video quality drops to rubbish.<br />
I welcome any advice / critique on improving the clip  (I am not a neuroscientist, so please keep it simple).<br />
Please leave a message on my user page if you think that another article could use a video clip to help WP users understanding the subject matter better.<br />
--[[User:Cookatoo.ergo.ZooM|Cookatoo.ergo.ZooM]] ([[User talk:Cookatoo.ergo.ZooM|talk]]) 15:03, 9 October 2010 (UTC)
:Thanks for doing this! I have a very small suggestion, that I will leave at your talk page. --[[User:Tryptofish|Tryptofish]] ([[User talk:Tryptofish|talk]]) 19:06, 9 October 2010 (UTC)
:Done.  The title has been changed to read "synapse".  --[[User:Cookatoo.ergo.ZooM|Cookatoo.ergo.ZooM]] ([[User talk:Cookatoo.ergo.ZooM|talk]]) 19:29, 9 October 2010 (UTC)
::Thanks! --[[User:Tryptofish|Tryptofish]] ([[User talk:Tryptofish|talk]]) 19:29, 9 October 2010 (UTC)
I have reduced the size of the video clip to 1.5MB.  Loading and playing with the old size of 13MB was a pain in the, erm I seem to have fogotten the medical term:)  Greetings.  --[[User:Cookatoo.ergo.ZooM|Cookatoo.ergo.ZooM]] ([[User talk:Cookatoo.ergo.ZooM|talk]]) 19:36, 14 November 2010 (UTC)

== Another mechanism to remove neurotransmitters ==

Astrocytes can help remove neurotransmitters, apart from the already enlisted [[Special:Contributions/129.180.166.53|129.180.166.53]] ([[User talk:129.180.166.53|talk]]) 15:04, 10 June 2012 (UTC)

== Terminology - "chemical synapse" vs. "presynaptic terminal" ==

What is the relationship between the two terms?  Are they simply different names for the exact same structure, or is one (I would guess "presynaptic terminal") a more specific term for part of the other?  This might or might not be relevant to a "History" section here. I know there are such things as "extra-synaptic" receptors (progesterone on ∂-subunit GABA-A neurons.<ref>{{cite journal|last1=Stell|first1=BM|last2=Brickley|first2=SG|last3=Tang|first3=CY|last4=Farrant|first4=M|last5=Mody|first5=I|title=Neuroactive steroids reduce neuronal excitability by selectively enhancing tonic inhibition mediated by delta subunit-containing GABAA receptors.|journal=Proceedings of the National Academy of Sciences of the United States of America|date=25 November 2003|volume=100|issue=24|pages=14439-44|pmid=14623958}}</ref>..), so I guess maybe a "''presynaptic'' terminal" might also have a specific meaning other than "just" another name for the synapse. [[User:Jimw338|Jimw338]] ([[User talk:Jimw338|talk]]) 19:23, 30 December 2014 (UTC)
{{reflist}}
:The presynaptic terminal is part of every chemical synapse, but it's only part of it, not the entire synapse. As the word "'''pre'''synaptic" implies, there should also be something "'''post'''synaptic", and there is: the postsynaptic cell membrane, where the receptors for the chemical transmitter are located. So the way a chemical synapse always works is: the presynaptic part releases the transmitter, the transmitter diffuses across the synaptic cleft, and then the transmitter binds to the postsynaptic receptor, eliciting a physiological effect.

:Extrasynaptic receptors can be anywhere on the membrane, not just at the synapse. So, in the example you cited, GABA is the chemical transmitter at the synapse. But progesterone, a hormone, is present all throughout the tissue. --[[User:Tryptofish|Tryptofish]] ([[User talk:Tryptofish|talk]]) 20:25, 30 December 2014 (UTC)

==Assessment comment==
{{Substituted comment|length=306|lastedit=20070508155742|comment=Rated "top" importance because [[neurotransmission]] redirects here and is highschool/SAT biology content. - [[User:Tameeria|tameeria]] 20:09, 28 April 2007 (UTC)

Rating changed to "high" since [[neurotransmission]] has been split into its own article. - [[User:Tameeria|tameeria]] 15:57, 8 May 2007 (UTC)}}
Substituted at 11:25, 29 April 2016 (UTC)

== synaptic cleft ==

What structure (force?) holds 2 neurons close together, but still separated in very small distance so that there will be functional synaptic cleft?  [[Kasutaja:Nimelik|Nimelik]] 7. january 2018, 13:31  <!-- Template:Unsigned --><small class="autosigned">—&nbsp;Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Nimelik|Nimelik]] ([[User talk:Nimelik#top|talk]] • [[Special:Contributions/Nimelik|contribs]]) 11:34, 7 January 2018 (UTC)</small> <!--Autosigned by SineBot-->
:That's an interesting question, but it's really a matter of the larger scale structure of the living tissue. The presynaptic cell and the postsynaptic cell are each held in position by the other cells surrounding them (and in some cases there are extracellular proteins that anchor one cell to another, although I'm not aware of one that traverses the synaptic cleft), and there is extracellular fluid, so a given amount of extracellular fluid occupies the space between the two cells. During tissue development, there are [[growth factor]]s that attract the presynaptic terminal to its postsynaptic target. --[[User:Tryptofish|Tryptofish]] ([[User talk:Tryptofish|talk]]) 20:26, 7 January 2018 (UTC)
::Try [https://en.wikipedia.org/w/index.php?search=synaptic+adhesion+molecule Wikipedia search: synaptic adhesion molecule] [[Special:Contributions/79.66.218.98|79.66.218.98]] ([[User talk:79.66.218.98|talk]]) 22:03, 12 April 2019 (UTC)

== Vesicle membrane recycling ==

:The article says ''"The membrane added by the fusion process is later retrieved by endocytosis and '''recycled''' for the formation of fresh neurotransmitter-filled vesicles"''. Does this mean that the  membrane originally used by the vesicle is ''actually recycled'' or that some arbitrary portion of the cell membrane is harvested when a new vesicle is to be created? There are implications with each. Literal recycling would require something which marks the vesical membrane region as recyclable. If arbitrarily harvested then the recycling is figurative. [[Special:Contributions/79.66.218.98|79.66.218.98]] ([[User talk:79.66.218.98|talk]]) 22:13, 12 April 2019 (UTC)