We might think that our thoughts are instantaneous, but they travel only at around 65 miles per hour. That’s very slow compared to the near light-speed of current in copper wires. Tiny gaps or synapses between nerve fibres impose a biological speed-limit on electrical signals flowing down nerves, forcing them to rely on slow chemical signals to bridge them. But low speed has its advantages in laboratory experiments because it now allows biologists to track individual neurons firing in real time using new dyes that light-up on detecting a voltage. This orange-stained cluster of nerve cells called a neuropil that coordinates the movement of gut muscles in crabs consists only of 30 cells (two cell bodies circled) that fire in sequence to orchestrate seamless muscle movements. Tracking the rhythmic crackle and fizz of the cells could help link the causes and effects behind malfunctions in more complex human nerve networks.
Written by Tristan Farrow
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