Tip to FO, linebackers really take a beating.
Smith’s research also suggests that even mild shocks to the brain can cause serious harm. If he hit his axons with gentle puffs of air, they didn’t swell and break. Nevertheless, there was a major change in their molecular structure. Axons create the electric current that allows them to send signals by drawing in negatively charged sodium atoms. A moderate stretch to an axon, Smith recently found, causes the sodium channels to malfunction. In order to keep the current flowing, the traumatized axons start to build more channels.
Smith suspects that such a mended axon may be able to go on working, but only in a very frail state. Another stretch—even a moderate one—can cause the axon to go haywire. Its additional sodium channels now malfunction, and the axon tries to compensate by creating even more channels. But these channels are now so defective that they start letting in positively charged calcium atoms. The calcium atoms activate enzymes that destroy the gates that slow the flow of sodium through the channels, so now even more sodium rushes in—and then more calcium, in a runaway feedback loop. The axon dies like a shorted-out circuit.