Mechanical changes in crab nerve fibers during action potentials.

A nerve impulse travelling along a crustacean nerve was found to be accompanied by a small, rapid movement of the nerve surface. The movement was 10-20 nm in amplitude and was concurrent with a rise in the "swelling pressure" of the order of 5 mg/cm2 for a nerve bundle. Initiation of an action potential at the site of cathodal polarization was preceded by a small, slow mechanical change in the nerve fiber. Anodal polarization produced a large mechanical change of the opposite sign. Tetrodotoxin and procaine suppressed rapid mechanical changes.