Neuron Diversity

The word neuron, as we understand it today, did not exist before 1891. In that year, German anatomist Wilhelm Waldeyer dubbed the discrete cells that form the nervous system neurons. (In 1896, Rudolph Albert von Kolliker coined the term axon to describe the long slender cables that transmit signals away from cell bodies. In 1889, William His named the thin branching fibers that ferry signals toward the cell body dendrites.) Today, more and more is being learned about them. Neurons are not all alike in the way they look or function. In fact, they differ from one another more than cells in any other organ. Some neurons send electrical signals along fibers that stretch several feet; other neurons’ branches extend only a few millimeters from the cell body. Some neurons possess a fractal beauty similar to that of ferns and corals (e.g., Purkinje cells may sport finely branched nets, like a sea fan), while some of their neighbors look more like tangled tumbleweeds. One neuron might appear more or less round under the microscope—like a firework frozen in climax—whereas another might spider through the brain like a daddy longlegs. The brain is a multi-diverse and inclusive universe.