Intro | Axon | Axon Hillock | Dendrites | Myelin Sheath | Nodes of Ranvier | Soma | Synapse | Terminal Buttons
Part 1: Image-Mapped Tutorial
Part 2: Matching Self-Test
Part 3: Multiple-Choice Self-Test
The Synapse (Greek, syn: union, association) is the point of connection between two neurons or between a neuron and a muscle or gland. Electrochemical communication between neurons takes place at these junctions. The synapse consists of three elements: 1) the presynaptic membrane which is formed by the terminal button of an axon, 2) the postsynaptic membrane which is composed of a segment of dendrite or cell body, and 3) the space between these two structures which is called the synaptic cleft. Some cells in the nervous system have as many as two hundred thousand synaptic connections.
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In 1871, Ramon y Cajal (a Spanish neuroscientist and artist) described the structure of the neuron, which he illuminated using a silver staining process. His poetic description of this cell type included (Restak, 1984): "The aristocrat among the structures of the body, with its giant arms stretched out like tentacles of an octopus to the provinces on the frontier of the outside world, to watch for constant ambushes of physical and chemical forces." With this work, which won him the Nobel Prize in 1906, he discovered that neurons are separated from one another by narrow gaps.
In 1906, an experimental physiologist named Sir Charles Scott Sherrington shared a brilliant insight based solely on behavioral data (Simmons, 1996). He speculated that a specialized type of communication occurs at these synapses (Restak, 1984): "It is as if the Milky Way entered upon some cosmic dance. Swiftly the brain becomes an enchanted loom where millions of flashing shuttles weave a dissolving pattern, always a meaningful pattern though never an abiding one; a shifting harmony of subpatterns."
In the century following the work of these early researchers, the interest in neuronal function has seemed to increase exponentially in momentum.
| References |
Restak, R. (1984). The brain. New York: Bantam Books.
Simmons, J. (1996). The giant book of scientists -- The 100 greatest minds of all time. Sydney: The Book Company.