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  University of Idaho
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  Psychology Dept.
  University of Idaho
  Design - P&D  CTI

The synapse basically contain three different sets of structures.  They contain the presynaptic element and all of its structures, the synaptic cleft (also called the synaptic gap) and the postsynaptic element and all of its structures.  It also contains a variety of other structures such as neurofilaments, and has glial cells and other structures located nearby. 

So, let’s talk about these in a little bit more detail.  As we saw in earlier lectures, the presynaptic element contains a variety of different structures.  It has structures within the lipid bilayer and contains the vesicles, channels, and a variety of other things.  And again, the picture is one that we saw earlier.  The postsynaptic element has all the structures that we have on either a dendrite or a Soma.  Again, it has a postsynaptic membrane, receptor sites, channels and a variety of other structures that we’ll talk about in more detail a little bit later. Again the picture on slide six is what you’ve seen before.

 Well what about the space in the middle between the pre and postsynaptic element.  As we remember, the pre and postsynaptic elements do not touch each other.  There’s a space in the middle that we call the synaptic cleft.  The synaptic cleft is basically a space, but it also contains neurofilaments which are bands of fibers that keep structures close together.  The picture that you might have seen earlier, on slide eight, is basically the combination of both sets of structures.

Now there are a variety of different types of synapses and I’ve listed three here.  When we talk about chemical-electrical synapses, the first one of these is an axosomatic synapse.  Others are axodendritic synapse and an axoaxonic synapse.  Basically, the name relates to what is touching what.  So, an axoaxonic synapse is basically an axon synapsing on another axon, and on and on.  So let’s talk about them in a little bit more detail.  Axosomatic synapses as we see in slide 10,  make a connection with a Soma.  So, you’re having a presynaptic element being in close proximity to a Soma.  These types of synapses tend to be regulatory. 

That’s in contrast to the next type of synapse (which we see in slide 11) and called an axodendritic synapse.  Here the connection is made with an axon and dendrite.  This is what you commonly refer to when you’re learning about these things in Introductory Psychology or other courses.  These types of synapses tend to be excitatory.

Finally, we have an axoaxonic synapse.  In an axoaxonic synapse, the connection is made from one axon on to another axon, usually at the hillock; but it could be anywhere along the axon proper.  Usually it connects with the presynaptic element.  This system tends to be inhibitory; and an axoaxonic synapse tends to do is shut down a second neuron.

Now there’s one other type of synapse that’s out there.  Those are called electrical synapses, and these have are called the gap junction. Not all synapses used in an electrical chemical system.  In an electrical synapse, what you have is a very, very, very close connection.  You actually have a discharge of electrical changes and polarity across the synapse site.  Usually, you see this in heart tissue and other types of things.  For us right now, those are not really that important, and so we’re not going to talk about them in detail.

So in general, what we’ve talked about now in the last several sections are a variety of different structures within the neuron and a little bit about how they connect with each other.  In the next section what we begin to talk about how these structures and systems relate to neurophysiology and neurochemistry.  So, we’re going to talk about different things in the action potential and different types of receptor sites that we have out there. So until then, we hope you’re enjoying your day and we will talk with you soon.