A 52-year-old woman from Delhi with chronic kidney disease (eGFR 18 mL/min) presents with severe muscle cramps, weakness, and an irregular heartbeat. Serum potassium is 6.8 mEq/L. An ECG is performed and shows tall, peaked T waves, a widened QRS complex (140 ms), and a prolonged PR interval (220 ms). She is given intravenous calcium gluconate immediately. Which of the following best describes the mechanism by which calcium gluconate reverses the cardiac manifestations of hyperkalemia?