The brain contains at least ten times more glia than neurons. Glia perform many jobs. Researchers have known for a while that glia transport nutrients to neurons, clean up brain debris, digest parts of dead neurons, and help hold neurons in place.
Current research is uncovering important new roles for glia in brain function. Explain the brain to your students with a variety of teaching tools and resources. Engage local scientists to educate your community about the brain. For Educators Log in. Also In Anatomy. Sex Differences in the Brain. The Mysterious, Multifaceted Cerebellum. Einstein's Brain. Spinal Cord. Help QBI research Give now. QBI newsletters Subscribe. Skip to menu Skip to content Skip to footer. Site search Search. Site search Search Menu.
Axons: the cable transmission of neurons. Home The Brain Brain anatomy. Axons and nerve degeneration Neurons cannot properly communicate if axons are damaged or broken. Image: istock. Types of neurons Axons Mitochondria Types of glia What are glia? In , Adolphe Hannover discovered what today we call the ganglion cells of the retina, the light-sensitive tissue at the back of the eye. Vladimir Alekseyevich Betz discovered the largest cells in the central nervous system, today known as Betz cells.
Cajal tried out various names for different kinds of neurons, as well as their tinier features. He called little bumps along the length of dendrites espinas , the Spanish word for thorns. Today, we call them dendritic spines.
So how many different types of neurons have scientists named so far? To find out, I contacted several neuroscientists who specialize in cell biology and what you could call neuron taxonomy. Perhaps unsurprisingly, no one has an exact number, but if you count all the types and subtypes in the entire nervous system, the answer is at least in the hundreds.
One great resource for exploring the cellular diversity of the nervous system is NeuroMorpho. Check out the Cell Types page and you'll encounter descriptive names like cone cell, climbing fiber, crab-like, medium spiny cell, pyramidal cell, chandelier cell and tripolar cell—each of which boasts a unique structure. Gordon Shepherd of Yale University pointed me to the Neuroscience Lexicon, a database that he and his colleagues are building.
Take a look for yourself at their current list of types of neurons. Here's what the Lexicon lists for distinct types of neurons in the cerebellum, an evolutionarily ancient part of the brain that helps coordinate movement:. And that's just one region of the brain. Remember that the human brain contains around billion neurons densely packed into three-pounds of tissue.
Consider that the human brain is one of the most complex structures we have ever tried to understand.
All those layers of fragile, excitable tissue folded upon one another. Within those folds we will surely discover new types of neurons of which we have no inkling at present. Next time on Know Your Neurons, we meet the members of the second broadest category of nervous system cells—the glia!
Bentivoglio, M. Life and Discoveries of Santiago Ramon y Cajal. Costandi, M. The discovery of the neuron. Principles of Neural Science, 4th ed. McGraw-Hill, New York. Mazzarello, P. A unifying concept: the history of cell theory. Nature Cell Biology 1, E13 - E15 doi Ferris Jabr is a contributing writer for Scientific American. Already a subscriber?
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