A Link to the Present

Mónica Folgueira, Wellcome Images.

When trying to tell neurons apart, count the limbs. While most human neurons feature at least three extensions, one variety–bipolar neurons–has only two, as seen here shining green in an adult zebrafish.

Their shape, with the branches of one end bringing in signals and the other relaying them away, makes the cells well suited to gathering and then passing on information.

For example, bipolar neurons in the inner nose connect the skin there with an odor-interpreting organ deeper in the brain. With similar connections in the retina and inner ear, these cells help link our brains with the external world via smell, sound, and sight.

About the Author

Charlie Wood

Charlie Wood is a science writer with a bachelor’s degree in physics from Brown University and a master’s degree in science journalism from New York University. In previous lives he taught physics in Mozambique and English in Japan, but these days he freelances from his home in New York.