What Causes Muscle Spasms Interfering In Movement?

Gregor, who works at a pesticide factory, comes to t he clinic complaining of muscle spasms that nterfere with his movement and breathing. S blood test shows that he has been contaminated with organophosphate pesticiide, which is and sacetylocholinesterase inhibitor. How would you explain to Gregor what this means? This is for my anatomy class.