Final answer:
Depolarization of the muscle membrane triggers the opening of sodium channels, allowing sodium ions to enter and causing an action potential to spread along the muscle fiber. In competitive inhibition, d-tubocurarine blocks the binding of acetylcholine to the motor end-plate, preventing muscle contraction. Continuous infusion of d-tubocurarine leads to fasciculations and eventually paralysis.
Step-by-step explanation:
Depolarization of the muscle membrane triggers the opening of sodium channels, allowing sodium ions to enter and causing an action potential to spread along the muscle fiber. In competitive inhibition, d-tubocurarine blocks the binding of acetylcholine to the motor end-plate, preventing depolarization and muscle contraction. Continuous infusion of d-tubocurarine causes the prolonged opening of sodium channels, leading to fasciculations (muscle twitches). When the sodium channels are eventually closed, paralysis occurs.