How to Improve Your Digestion with Nutrition

1. As food is moved through the digestive tract the pancreas and small intestine release digestive enzymes according to signals based on contents of the duodenum. Briefly describe the stimuli that trigger secretion of enzymes from exocrine cells of the pancreas and small intestinal mucosa. You should briefly describe how they are similar, and how they differ. 

The exocrine system of the pancreas comprises the acinus and its network of ducts. Pancreatic secretion is mildly stimulated through the vagal intervention that occurs following stimulation of senses including smell, sight, or taste by food or stretching of the stomach wall. Sullivan (2009) observed that strong pancreatic stimulation occurs when chyme flows from the stomach into the duodenum. Chyme is acidic and stimulates release of secretin by S cells. Secretin stimulates secretion of water and the alkaline contents of the pancreatic juices that flush the juices into the duodenum. Chyme also has fatty acids and proteins, which in the duodenal acidic pH, trigger the release of cholecystokinin hormone that in turn stimulates the secretion of pancreatic juices. Cholecytokinin stimulates contraction of the gall bladder and release of bile into the duodenum. Pancreatic acinar cells are also stimulated to secret digestive juices by gastrin, which is secreted in by the stomach cells. 

The intestinal phase of digestion occurs in the duodenum. Secretion of enzymes in the small intestine is triggered by the arrival of chyme from the stomach. According to Sullivan (2009), the small intestine is stimulated in the same manner as the pancreas to secret digestive enzymes. The arrival of chyme from the stomach causes distension of the duodenum causing which stimulates its cells to secret gastrin, cholecystokinin, and secretin, and subsequent stimulation of the endocrine cells of the duodenum in a similar fashion to the pancreas. The main difference between pancreatic and intestinal phases of digestion is that the latter triggers suppression of gastric secretion and motility to allow time for processing of chyme in the duodenum before receiving more from the stomach. 

2. “Metabolism” is a word that has entered everyday speech. In physiological terms, what is metabolism? At a cellular level, how are metabolic processes controlled? 

In physiology, metabolism refers to a series of chemical processes involved in catabolism and anabolism. Catabolism is the breakdown of food component to release energy, while anabolism is the consumption of energy from catabolic reactions to synthesize larger compounds. Therefore, physiological metabolism can be summed as the chemical processes through which energy sis produced and used to sustain critical life functions. 

Regulation of cellular metabolism takes into account a number of factors. for metabolism to occur at cellular level, there must be a substrate and enzymes to catalyze the chemical process (Sullivan, 2009). Therefore, cells regulate the process of metabolism through control of substrate availability, concentration of the enzymes, and regulating the activity of the enzyme. The regulatory mechanism is driven by the needs of the cells, hence, the cell is able to speed up or slow down metabolic processes through either of the regulatory pathways to meet its demands. 

3. For each of the following digestive enzymes identify which organ or gland it is produced in, and which macromolecules it plays a role in digesting: 

4. If you take a bite of something that is highly unappealing (for example meat that tastes rotten) what is the response of the salivary glands? What does this tell us about the regulation of digestive enzyme secretion from the salivary glands? 

When an individual takes a bite of an unappealing food, the salivary gland responds by secreting saliva in a similar way it would do if it were a bite of something tasty. The conclusion that can be made from the observation is that salivary glands have an automatic response in secretion of digestive enzymes. The process occurs irrespective of the taste of the food. This implies that secretion is dependent on stimulation of the taste buds, the taste notwithstanding. Secretion of saliva, which contains digestive enzymes, is triggered by the placement of food in the mouth; taste is a secondary stimulant. 

5. Based on your understanding of nitrogen balance identify which condition exists in each of the following examples: 

An anorexic patient is rapidly losing skeletal muscle tissue 

Malnutrition – intake of inadequate balance diet causes the body to turn to its reserves, specifically glycogen which is stored in the muscles. 

A weight lifter who is increasing lean body mass 

Muscle hypertrophy – the condition occurs because weight lifting damages muscles, hence signals are sent to the body to turn ingested proteins into new muscle tissue, increasing body muscle mass in the process. 

A pregnant woman proceeding through a healthy pregnancy 

Efficient protein metabolism – nitrogen balance increases towards the end of pregnancy, implying efficient protein metabolism and use in the later stages of pregnancy. 

A serious burn victim who is receiving protein supplements but still losing weight 

Muscle wasting – serious burns lead to extended bed rest, which in turn causes loss of muscle mass due to inactivity. 

6. Would you classify regulation of gastric juice as a positive or negative feedback loop? Justify your answer. 

Regulation of gastric juice can be classified as a positive feedback loop. First, the regulatory process does not seek to bring the gastric system to anything closer to homeostasis, which rules out the possibility for negative feedback loop. Second, gastric regulation often seeks to lower the pH of the stomach by increasing the secretion of hydrochloric acid. The process moves the gastric system further away from homeostasis equilibrium, which is synonymous with the reaction in a positive feedback loop. 

References 

Sullivan, R. J. (2009).  Digestion and nutrition . Infobase Publishing.