A 28-year-old male from Mumbai presents to the emergency department with acute-onset muscle weakness and paresthesias in both lower limbs. He reports consuming a large quantity of raw cashew nuts 2 hours prior. On examination, he has flaccid paralysis of bilateral lower limbs with preserved sensation. Serum potassium is 7.2 mEq/L (normal 3.5–5.0). ECG shows peaked T waves and prolonged PR interval. Which of the following best explains the neurophysiological basis of his muscle weakness?