<p>Gap junctions can couple cells directly electrically. Cell types electrically coupled via gap junctions include neurons, the pancreatic islets of Langerhans <a href="http://onlinelibrary.wiley.com/doi/10.1113/jphysiol.1997.sp021899/pdf" rel="nofollow noreferrer">(Andreu <em>et al</em>, 1997)</a> and cardiac cells (Fig. 1.). In contrast to chemical synapses, information transfer via electrical "synapses" (gap junctions) is nearly instantaneous. In chemical information flow, the synapse is the rate limiting step, because it depends on the passive diffusion of neurotransmitters across the synaptic cleft. </p>

<p><a href="https://i.sstatic.net/QoRes.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/QoRes.jpg" alt="![![enter image description here"></a><br>
<sup>Fig. 1. The pacemaker potential in cardiac muscle cells spreads rapidly across the surface of the heart to generate synchronous muscle contraction. Source: <a href="http://www.austincc.edu/apreview/PhysText/Cardiac.html" rel="nofollow noreferrer">Austin Community College</a>.</sup></p>

<p>Moreover, in a structure such as a brain nucleus many cells can be coupled. In other words, if all cells in a tissue contain gap junctions, all these cells are directly electrically coupled, not just those cells directly touching each other. In a way, all cells in such a tissue are in open connection with each other. This means that when one cell fires, it can theoretically activate <em>all the connected cells</em> to fire an action potential in near-synchrony.</p>

<p>Hence, gap junctions allow for <strong>synchronous activation of inter-connected neurons</strong>, both  in the spatial and temporal domain.</p>

<p>While this can be the preferred mode of operation of firing in some neuronal structures such as the olivary nucleus <a href="http://jn.physiology.org/content/94/4/2447" rel="nofollow noreferrer">(Leznik &amp; Llinás, 2005)</a>, it can theoretically lead to trouble in case pathological synchronization is established, leading to epileptic activity <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC321041/" rel="nofollow noreferrer">(Dudek, 2002)</a>.</p>

<p>Whether we know little, or much of gap junctions is subjective. However, it is certainly true that way more research is available on chemical neurotransmission than on electrical transmission. Likewise, many more medications target chemical transmission than electrical neurotransmission.    </p>

<p><sup><strong>References</strong><br>
<strong>-</strong> <a href="http://onlinelibrary.wiley.com/doi/10.1113/jphysiol.1997.sp021899/pdf" rel="nofollow noreferrer">Andreu <em>et al</em>, <em>J Physiol</em> (1997), <strong>498</strong>(3): 753-61</a><br>
<strong>-</strong> <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC321041/" rel="nofollow noreferrer">Dudek, <em>Epilepsy Curr</em> (2002); <strong>2</strong>(4): 133–6</a><br>
<strong>-</strong> <a href="http://jn.physiology.org/content/94/4/2447" rel="nofollow noreferrer">Leznik &amp; Llinás, <em>J Neurophysiol</em> (2005); <strong>94</strong>(4): 2447-56</a></sup></p>

CC BY-SA 3.0
2015-08-28T15:57:31.583Z
Thank you for the detailed answer (and the helpful diagram)!
Sydney Maples
CC BY-SA 3.0
2015-08-28T10:37:24.973Z
2015-08-28T23:53:41.053Z
2015-08-28T23:53:41.053Z
AliceD
<p>I was reading <a href="http://lcn.epfl.ch/~gerstner/SPNM/node3.html#SECTION01113000000000000000">this</a> and I found the following sentences:</p>

<blockquote>
  <p>Apart from chemical synapses neurons can also be coupled by electrical synapses, so-called gap junctions. Specialized membrane proteins make a direct electrical connection between the two neurons. Not very much is known about the functional aspects of gap junctions, but they are thought to be involved in the synchronization of neurons.</p>
</blockquote>

<p>Do we really know very little about the functional aspects of gap junctions? And how are they involved the 'synchronization' of neurons?</p>

<neuroscience><neurophysiology>
What are 'gap junctions' (electrical synapses) for?
Sydney Maples
# What are 'gap junctions' (electrical synapses) for?

(Asked by: username_0 on 2015-08-28)

I was reading [this](http://lcn.epfl.ch/~gerstner/SPNM/node3.html#SECTION01113000000000000000) and I found the following sentences:

> Apart from chemical synapses neurons can also be coupled by electrical synapses, so-called gap junctions. Specialized membrane proteins make a direct electrical connection between the two neurons. Not very much is known about the functional aspects of gap junctions, but they are thought to be involved in the synchronization of neurons.

Do we really know very little about the functional aspects of gap junctions? And how are they involved the 'synchronization' of neurons?

**Tags:** neuroscience, neurophysiology


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## 1 answers

### Answer by username_1 on 2015-08-28. Score: 5 | Accepted answer

Gap junctions can couple cells directly electrically. Cell types electrically coupled via gap junctions include neurons, the pancreatic islets of Langerhans [(Andreu *et al*, 1997)](http://onlinelibrary.wiley.com/doi/10.1113/jphysiol.1997.sp021899/pdf) and cardiac cells (Fig. 1.). In contrast to chemical synapses, information transfer via electrical "synapses" (gap junctions) is nearly instantaneous. In chemical information flow, the synapse is the rate limiting step, because it depends on the passive diffusion of neurotransmitters across the synaptic cleft.

[![![![enter image description here](https://i.sstatic.net/QoRes.jpg)](https://i.sstatic.net/QoRes.jpg)  
Fig. 1. The pacemaker potential in cardiac muscle cells spreads rapidly across the surface of the heart to generate synchronous muscle contraction. Source: [Austin Community College](http://www.austincc.edu/apreview/PhysText/Cardiac.html).

Moreover, in a structure such as a brain nucleus many cells can be coupled. In other words, if all cells in a tissue contain gap junctions, all these cells are directly electrically coupled, not just those cells directly touching each other. In a way, all cells in such a tissue are in open connection with each other. This means that when one cell fires, it can theoretically activate *all the connected cells* to fire an action potential in near-synchrony.

Hence, gap junctions allow for **synchronous activation of inter-connected neurons**, both in the spatial and temporal domain.

While this can be the preferred mode of operation of firing in some neuronal structures such as the olivary nucleus [(Leznik & Llinás, 2005)](http://jn.physiology.org/content/94/4/2447), it can theoretically lead to trouble in case pathological synchronization is established, leading to epileptic activity [(Dudek, 2002)](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC321041/).

Whether we know little, or much of gap junctions is subjective. However, it is certainly true that way more research is available on chemical neurotransmission than on electrical transmission. Likewise, many more medications target chemical transmission than electrical neurotransmission.

**References**  
**-** [Andreu *et al*, *J Physiol* (1997), **498**(3): 753-61](http://onlinelibrary.wiley.com/doi/10.1113/jphysiol.1997.sp021899/pdf)  
**-** [Dudek, *Epilepsy Curr* (2002); **2**(4): 133–6](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC321041/)  
**-** [Leznik & Llinás, *J Neurophysiol* (2005); **94**(4): 2447-56](http://jn.physiology.org/content/94/4/2447)

> **Comments:**
> **username_0**: Thank you for the detailed answer (and the helpful diagram)!  

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