Stellate ganglions (aka the cell the giant axon in a squid). Most biology students are familiar with this cell since the first recording of neuron’s activity was done with it in the 1930’s (by Hodkin and Hukley who later received a Nobel Prize for the experiment). But why did they use a squid? Because they have giant axons! Their setup (which they learned at Marine Biological Laboratory in Massachusetts) involved dissecting out the stellate ganglion (a cell) and cutting a long fiber (the axon) off. The axon was cut at both ends, clamped on one side with a tweezer and then squeezing out the contents of the cell fiber with another tweezer moving away from it [1]. You can actually watch a video of their setup on youtube. Anyway, no mammalian cells are big enough to so crudely dissect out or squeeze.
Biologists learn all about the impact this stellate ganglion experiment had on neuroscience, but we rarely hear what the cell naturally does; it’s involved in a quick escape. The squid’s stellate ganglion runs through the whole body innervating a siphon that squirts out water for quick underwater movements. Humans also have a stellate ganglion, but this is a cluster of neurons in the neck that sends projects to the face and arm. Though our stellate ganglion is also involved in reflexes, it’s more involved in blood flow, sweat, and pain rather than directing movement.
So do giant squids don’t have giant giant fibers? Maybe not; one of the people who taught Hodkin and Huxley to prep a giant axon for recording wondered the same thing and dissected a 4ft long squid. He is said to have reported that, “The nerves of the mantle muscles are arranged in this genus differently from any other I have seen. Those in the front part of the mantle arise from a relatively small stellate ganglion, in the usual way.” [2]
[1] Bear, R S., Schmatt F O., & Young J Z. (1937). Investigations on the protein constituents of nerve axoplasm. Proc. Roy. Soc. B, 123, 520-529.
[2] (2013) . “How big is the GIANT Squid Giant Axon?” The Cellular Scale. http://cellularscale.blogspot.com/2013/01/how-big-is-giant-squid-giant-axon.html
Originally posted on Instagram October 15, 2019
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