A 28-year-old woman from rural Maharashtra presents to the emergency department with progressive muscle weakness over 3 days. She reports difficulty chewing and swallowing, followed by weakness in the limbs. On examination, she has ptosis, dilated pupils, and a dry mouth. Her vital signs show tachycardia (110/min) and hypertension (160/95 mmHg). She admits to consuming homemade pickle 2 days before symptom onset. Neurological examination reveals descending paralysis with preserved sensation. Which of the following best explains the mechanism of her neuromuscular dysfunction?