Gastric acid production is tightly regulated by neural, hormonal, and paracrine pathways. The vagus nerve stimulates acid secretion via the release of acetylcholine. Hormones like gastrin and histamine also play significant roles. Gastrin, produced by G-cells in the stomach, stimulates parietal cells directly. Histamine, released by enterochromaffin-like (ECL) cells, binds to H2 receptors on parietal cells, further promoting acid secretion.