If the na+ voltage-gated channels in a muscle cell open, what will be the result?

If the Na+ voltage-gated channels in a muscle cell open, the Na (sodium) ions rush inside the muscle cell and makes the cell more positive as Na ions carry positive charge on it. Due to the entry of positively charged ions inside the cell, the cell becomes less negative and more positive. This is called depolarization of cell.

If Na+ voltage-gated channels open, Na ions will enter the cell and make it less negative or more positive. The neuromuscular junction is a chemical synapse. ... This action potential is propagated along the sarcolemma of the muscle fiber, which triggers sliding of the myofilaments for muscle contraction.