I had no idea that neurons came in such a beautiful diversity of shapes. Each of these neurons has a different function, too: A. Purkinje cell B. Granule cell C. Motor neuron D. Tripolar neuron E. Pyramidal Cell F. Chandelier cell G. Spindle neuron H. Stellate cell.
The image, drawn by science journalist Ferris Jabr, comes from a post of his on the Brainwaves blog, explaining the discovery of the neuron—and the first realizations that not all neurons looked the same. It's the first part of a new series he's working on called "Know Your Neuron".
When the leading anatomists of the 19th century examined fragile nervous tissue with the best microscopes available to them, they identified cell bodies that sprouted many tangled projections. German histologist Joseph Gerlach's observations convinced him that the fibers emerging from different cell bodies fused to form a continuous network, a seamless web known as the "reticulum." His ideas were popular. Many researchers accepted that, unlike the heart or liver, the brain and nervous system could not be split up into distinct structural units.
In 1873, Italian physician Camillo Golgi discovered a chemical reaction that allowed him to examine nervous tissue in much greater detail than ever before. For some reason, hardening a piece of brain in potassium dichromate, and subsequently dousing it with silver nitrate, dyed only a few cell bodies and their respective projections in the tissue sample, revealing their complete structures and exact arrangement within the unstained tissue. If the reaction had stained all the neurons in a sample, Golgi would have been left with an unfathomable black blotch, as though someone had spilled a bottle of ink. Instead, his technique yielded neat black silhouettes against a translucent yellow background.
Read the rest of Know Your Neuron: The Discovery and Naming of the Neuron