Hormonal Control of Digestion

The control of the digestive process is one that involves an interaction between the nervous system, the endocrine system, the circulatory system, and the digestive system. The body produces enzymes that are released into the digestive tract to break down food molecules into their monomers for absorption. Hormones help control the digestive process by use of a negative feedback loop.

When food enters the stomach, it stimulates the secretion of gastrin, which signals the stomach to secrete hydrochloric acid. A low pH inhibits the release of gastrin. This negative feedback mechanism ensures that the pH of the stomach is low enough to activate pepsinogen but not so low that it damages the stomach wall.

The arrival of food in the duodenum stimulates the secretion of the hormones cholecystokinin and secretin. These hormones have a number of functions, including inhibiting the contraction of the stomach, stimulating the release of pancreatic secretions, and contraction of the gall bladder to secrete bile. 

Watch

Watch the following video about the hormonal regulation of digestion.

Pay particular attention to the positive feedback that reinforces the continued release of gastric secretions into the stomach. In addition, watch for the negative feedback that shuts off the release of these secretions when stomach digestion is complete.

For more information about feedback and homeostasis, check page 203 in the textbook.

 Dietitians

As you have seen in Lesson 2, diet plays an important role in keeping people's bodies in homeostasis. With such a wide range of foods and supplements available, it is easy to become confused about meeting proper nutritional needs.

This is where a trained registered dietitian (RD) can be very useful because an RD can provide information to you about food choices. RDs also assist in the development and promotion of consumer products as well as helping to manage food services in health institutions. A dietitian can be important to individuals even if they're not elite athletes who push their bodies to extremes.

Kelly Anne Erdman is a former Olympian and Registered Dietitian. She provides nutritional information to top-level athletes in the hope that they will be at their peak performance on competition day. The food and supplements that an athlete consumes can mean the split-second difference between a gold medal and last place.