Final answer:
Ghrelin is a neuropeptide secreted by the stomach that functions to initiate eating, signaling the brain that the body needs to consume food. It is one of several hormones instrumental in digestion control, along with others such as gastrin, secretin, and CCK.
Step-by-step explanation:
Ghrelin is a neuropeptide that is secreted from the stomach and functions to initiate eating. The correct answer to the question is: 1) stomach - initiate eating. Ghrelin acts as a hunger signal, informing the brain that the body needs energy and that it is time to consume food. It is one of several hormones involved in the regulation of digestion along with gastrin, secretin, cholecystokinin (CCK), and others.
These hormones play various roles in the digestive process. For example, gastrin signals the secretion of gastric acid, secretin stimulates the pancreas to release a bicarbonate solution, and CCK promotes the secretion of digestive enzymes from the pancreas and the release of bile from the gallbladder. All these hormones are crucial for proper digestion and are secreted by specialized epithelial cells in response to the presence of food.