Proposed mechanisms of calcium entry into stretch-injured axons. 1, Strain on the axonal membrane inducing an abnormal influx of Na⁺ through mechanosensitive sodium channels. 2, In response, reversal of axonal Na⁺–Ca²⁺exchangers (a) and activation of voltage-gated calcium channels (b), collectively contributing to a pathological influx of Ca⁺² into the axons.