Fig. 4
Diagram of AP conduction within the NMJ. A In the normal NMJ, (1) a nerve AP arrives at the nerve terminal and produces rapid depolarization, (2) VGCCs opening and Ca2+ entry, (3) the transmission vesicles fusion to the pre-membrane and release ACh into the cleft, (4) ACh bind to their post-synaptic receptors and generate a localized EPP at the crest of JFs, (5) EPP arrive the valleys of JFs and produces rapid depolarization, (6) VGSCs opening and generate of a muscle AP, (7) VGSCs on the neighbor JFs induced opening by voltage gating, resulting saltatory conduction happening, (8) Orthogonally aligned JFs propagate the AP along the long axis and drive the muscle fiber contraction. B. In VGSCs deficient JFs, muscle AP is not initiated by the Na+ inflow of VGSCs. To spread the AP throughout the whole NMJ region, it needs to activate more VGCCs and release more ACh vesicle quanta. Figures C and D are the plane views of A and B, respectively