Final answer:
The peptide hormone that increases the activity of gastric glands is c) gastrin. It stimulates the secretion of gastric acid, which is essential for digestion, unlike insulin and glucagon that regulate blood glucose levels.
Step-by-step explanation:
The peptide hormone that increases the secretory activity of gastric glands is gastrin. This hormone is responsible for stimulating the secretion of gastric acid necessary for the digestive process. Hormones like insulin and glucagon are secreted by the pancreas in response to blood glucose levels, but they do not directly influence the secretory activity of the gastric glands. Insulin helps to decrease blood glucose levels by promoting glucose absorption into various tissues, while glucagon has the opposite effect, increasing blood glucose levels by promoting the conversion of stored glycogen into glucose. Gastrin, on the other hand, is directly linked to the gastrointestinal system's function.