Of course they could have missed some, too. In the five pairs they found 15, 17, 8, 3, and 10 connections. The post-synaptic cells were all pyramidal cells except one was a spiny stellate cell. The presynaptic cells were one basket cell, three dendrite-targeting cells, and one double bouquet cell. Note in this paragraph they are literally talking about 5 specific pairs of cells, where they trace both cells in EM. Each synaptic knob communicates with a dendrite or cell body of another neuron, the point of contact being a synapse. Axon terminals have knob-like swellings at the very end called synaptic knobs or end buttons. A basket cell innervated a pyramidal cell via fifteen release sites the numbers of synapses formed by three dendrite-targeting cells on pyramidal cells were seventeen and eight respectively, and three on a spiny stellate cell the interaction between a double bouquet cell and a postsynaptic pyramidal cell was mediated by ten synaptic junctions. Through synaptic gaps, a typical neuron may interconnect with thousands and tens of thousands of other neurons. Though this can mean that cells receive and send input to 1000s of different cells, it's also very common for there to be multiple individual synapses between two specific cells.įor some examples, Tamas et al 1997 looked at synapses made from inhibitory interneurons to excitatory cells in visual cortex:Īll presynaptic cells established multiple synaptic junctions on their postsynaptic Though a synapse is a one-to-one connection, axons make multiple synaptic contacts as do dendrites. There can be multiple connections between two given cells Classical concepts of neuronal organization have been based on the motoneuron as a model. Some neuromodulators (and sometimes traditional neurotransmitters) are not released synaptically, though, and are just dumped into the extracellular space from where they diffuse in to the cleft or bind outside the synaptic region. It's as if you put the palms of your two hands together. There's no room for more than one cell to be directly involved in this area, it's one membrane closely coupled with another membrane. There's a dense, dense gathering of cellular machinery at the synapse that creates a dark electron-dense region shown by the arrows. You should gather from these images that these are super organized structures. Here's some EM pictures of synapses, from Wikimedia commons:
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