Question

There are a few short reflexes of the GI system. Below is a list of short reflexes. Research each reflex and describe its action on the GI tract. Your textbook will have information on each of these.

1)

There are a few short reflexes of the GI system. Below is a list of short reflexes. Research each reflex and describe its action on the GI tract. Your textbook will have information on each of these.

Short Reflex	Action
Gastrocolic reflex
Enterogastric reflex
Gastro-ileal reflex

Answer 1

Enteric nervous system, commonly called as second brain,is a part of the peripheral nervous system that directly controls the gastrointestinal system.

The system consists of two plexuses, the submucosal and the myenteric. The myenteric plexus increases the tone of the gut and the velocity and intensity of contractions. The submucosal plexus is involved with control over local secretion, absorption, and muscle movements.

Short reflexes to the digestive system provide shortcuts for the enteric nervous system to act quickly and effectively.That include the following reflexes:

■ Gatrocolic reflex

Involves an increase in the motility of the colon, creates the urge to defecate along with the gastroileal reflex, and helps make room for food in the stomach.

The reflex includes the autonomic nervous system, the enteric nervous system, and cells of the GI tract that regulate endocrine functions.

It is a physiological reflex that controls the motility of the lower gastrointestinal tract after a meal.

As a result of the gastrocolic reflex, the colon has increases the its motility due to the stretch of the stomach with the ingestion of food.

By controlling the peristalsis and and moving the ingested food to the rectum,
the gastrocolic reflex allows consumption of more food.

Reflex in the large intestine causes a spike in electrical activity within minutes of food consumption. The gastrocolic reflex initiates and controls migrating motor complexes throughout the colon.

Several neuropeptides are suspected mediators of the reflex, including cholecystokinin, serotonin, neurotensin, and gastrin.

Three centers of control have been identified and studied and include myogenic control, hormonal control, and neural control.

The sigmoid colon is the region most affected during the phasic response of digestion, which consists of cyclical periods of contraction followed by relaxation to propel food distally toward the rectum.

When food enters the rectum and drives pressures up, the gastrocolic reflex stimulates expulsion of the contents of the rectum via defecation.

People with an overactive gastrocolic reflex may develop Irritable Bowl movement (IBS), especially in babies.IBS is not a specific disease ,it is collection symptoms including : bloating,gas, ,constipation,gas,diarrhea, or both cramping abdominal pain.

■ Enterogastric reflex

It is a feedback mechanism to regulate the rate at which partially digested food leaves the stomach and enters the small intestine.

Receptors in the duodenal wall detect distension of the duodenum caused by the presence of chyme(partially digested food) and also raised acidity of the duodenal contents due to excess gastric acid.

The enterogastric reflex is stimulated by the presence of acid levels in the duodenum at a pH of 3–4 or in the stomach at a pH of 1.5. When this reflex is stimulated, the release of gastrin from G- cells in the antrum of the stomach is shut off. In turn, this inhibits gastric motility and the secretion of gastric acid.

The send signals are send through the parasympathetic nervous system, causing reflex inhibition of stomach-wall muscles responsible for the stomach emptying.

The signals causes the stretching of the wall of the duodenum results in inhibition of gastric motility and reduced rate of emptying of the stomach.

Emptying of stomach is through pylorus
(the opening from the stomach into the duodenum) when duodenum is over loaded and stimulated.

■ Gastroileal reflex

The gastroileal reflex works with the gastrocolic reflex to stimulate the urge to defecate. This reflex is stimulated by the opening of the ileocecal valve and moves the digested contents from the ileum of the small intestine into the colon for compaction.

Initiation of the reflex causes peristalsis in the ileum and the opening of the ileocecal valve ,which allows the emptying of the ileal contents into the large intestine, or colon.This in turn stimulates colonic peristalsis and an urge to defecate.

Gastroileal reflex is one of the ways in which gastric motility influences intestinal motility.When there is vigorous gastric peristalsis of increased secretion, it stimulates peristalsis in the ileum.

This causes the ileal contents to be pushed into the colon, in turn stimulating colonic peristalsis and an urge to defecate.

Local and Extrinsic Nervous Innervations control ileal and colonic Motility.Colonic Stretch receptors Initiate a local contraction reflex mediated by myenteric plexus.
As part of this reflex relaxation of the colon to accept material from the ileum.

Ingesting a meal increases ileal contraction and relaxes the ileocecal sphincter. This is the gastroileal reflex, which appears to be mediated by extrinsic nerves.