As you read this sentence, your eyes dart back and forth many times each second. As they hop, they take in letters for your brain to assemble into ideas. It’s these glowing red motor neurons that make it all possible, letting you point those pupils at will.
The neurons responsible for executing your eye movements start out in the middle of the brain, as seen here in a 10-day old chicken egg, before coming together and exiting the brain as a braided nerve fiber. When this fiber nears the eye, that bundle splits up, and its branches stick themselves into the various muscles that grip the eyeball. Electrical signals passing through the nerve bundle make the appropriate muscles tighten up, letting your gaze hop from one side of the page to the other.
Charlie Wood is a science writer with a bachelor’s degree in physics from Brown University and a master’s degree is 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.
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