What makes pancreas secrete?

The pancreas is a glandular organ that secretes enzymes that help digest food and hormones that help regulate blood sugar levels. The pancreas secretes these substances in response to various stimuli, including:

1. Neural Stimuli: The vagus nerve, which is a major nerve that connects the brain to the digestive organs, plays a crucial role in regulating pancreatic secretions. When we smell, see, or think about food, the vagus nerve stimulates the pancreas to secrete digestive enzymes even before food enters the stomach. This process is known as the cephalic phase of pancreatic secretion.

2. Hormonal Stimuli: The presence of food in the stomach and small intestine triggers the release of hormones that stimulate the pancreas to secrete digestive enzymes. The most important of these hormones are:

* Cholecystokinin (CCK): Cholecystokinin is released by the small intestine in response to the presence of fats and proteins. It stimulates the pancreas to secrete enzymes, including lipases, amylases, and proteases, which help break down fats, carbohydrates, and proteins, respectively.

* Secretin: Secretin is released by the small intestine in response to the presence of acidic chyme from the stomach. It stimulates the pancreas to secrete a bicarbonate-rich fluid that helps neutralize the acidity and create a more alkaline environment for the digestive enzymes to work effectively.

* Gastrin: Gastrin is released by the stomach in response to the presence of food. It stimulates the pancreas to secrete digestive enzymes, but its primary role is to regulate gastric acid secretion and muscle contractions in the stomach.

3. Local Stimuli: The presence of certain nutrients, such as carbohydrates and proteins, can directly stimulate the pancreatic cells to secrete digestive enzymes. This is known as the local phase of pancreatic secretion.

4. Parasympathetic Stimulation: The parasympathetic nervous system, particularly through the vagus nerve, plays a role in stimulating the pancreas to secrete enzymes and bicarbonate. Activation of the parasympathetic nerves enhances pancreatic secretions.

It's important to note that the pancreas does not secrete all of its substances simultaneously. The secretion of specific enzymes and hormones is tightly regulated to match the type and amount of food being digested.