Which of the following hormones regulates secretions into the digestive tract?

Gastrin is the hormone that plays a key role in regulating secretions into the digestive tract. It is produced by G cells in the stomach lining in response to food intake. Once released, gastrin stimulates the parietal cells in the stomach to secrete hydrochloric acid, which is crucial for digestion. It also promotes the release of pepsinogen, an inactive enzyme that is converted to pepsin in the acidic environment of the stomach, aiding in protein digestion. Additionally, gastrin increases gastric motility, which further facilitates the digestive process.

In contrast, insulin primarily regulates glucose metabolism and helps cells take up glucose from the bloodstream. Cortisol is involved in the stress response and has various metabolic functions, including glucose regulation and anti-inflammatory effects, but does not have a direct role in stimulating digestive secretions. Glucagon works to increase blood glucose levels by promoting the release of glucose from the liver but is not involved in the regulation of secretions into the digestive tract. Therefore, gastrin is the hormone specifically responsible for stimulating digestive secretions.