Digestive System Regulation and Summary

Flashcards covering the regulation of the digestive system, including nervous and endocrine control, gastric phases, and specialized reflexes.

According to the transcript, what are the two main reasons for controlling digestion?

To maximize digestion and absorption by creating specific conditions in the GI tract, and to slow down movements and secretions during the post-absorptive phase to conserve energy.

Which two key systems mediate the automatic digestive reflexes in the gastrointestinal tract (GIT)?

The Nervous System and the Endocrine System.

What is the enteric nervous system (ENS) often referred to as, and approximately how many neurons does it contain?

It is often called the "2nd brain" and contains approximately $100$ million neurons.

Where is the submucosal plexus located and what is its primary function?

It is located in the submucosa and controls secretions.

Where is the myenteric plexus located and what does it control?

It is located between the circular and longitudinal muscle layers and controls motility.

How does the Vagus nerve (parasympathetic) affect the activity of the GIT?

Increased parasympathetic input from the Vagus nerve leads to increased activity of the GIT.

In what year did Ivan Pavlov win the Nobel Prize for his research on the neural control of secretions?

$$1904$$

What is the nature of the control of salivary secretion according to the transcript?

It is entirely nervous; no hormones are involved.

Where is the salivary center located in the brain?

In the medulla oblongata.

Which three main hormones are involved in the endocrine control of the digestive system?

Gastrin, Cholecystokinin (CCK), and Secretin.

From which specific cells and location is Gastrin released?

G-cells located in the base of the stomach gastric pits.

Which phase of gastric secretion occurs before food arrives in the stomach and prepares it for digestion?

The Cephalic phase.

How long does the gastric phase of secretion typically last?

$3$-$4$$ hours.

During the intestinal phase, which two hormones decrease gastric secretion and motility?

Cholecystokinin (CCK) and Secretin.

Which cells secrete histamine to activate parietal cells for gastric acid secretion?

Enterochromaffin-like (ECL) cells.

What is the function of Somatostatin released from D cells in the stomach?

It directly inhibits gastric acid secretion from parietal cells and indirectly acts on ECL and G cells.

What triggers the release of Cholecystokinin (CCK) in the duodenum?

The presence of fats and peptides in chyme.

What are the primary effects of Cholecystokinin (CCK) on the gall bladder and pancreas?

It causes contraction of the gall bladder to release bile and increases the secretion of pancreatic enzymes.

What is the stimulus for Secretin release and what is its primary effect on pancreatic juice?

Stimulated by acidic chyme in the duodenum, it increases the production of bicarbonate-rich pancreatic juice to neutralize the acid.

What are the effects of the Enterogastric Reflex on gastric and small intestine activity?

It decreases gastric juice and motility to slow stomach emptying, increases segmentation in the small intestine, and causes contraction of the pyloric sphincter.

Which reflex is triggered by the filling of the stomach and results in peristalsis in the small intestine and relaxation of the ileocaecal sphincter?

The Gastroileal reflex.

What is the result of the Gastrocolic Reflex and how often does it typically occur?

It results in powerful peristaltic contractions (mass peristalsis) from the middle of the colon, occurring $3$-$4$$ times per day.

What are the two layers of smooth muscle found in the Muscularis Externa?

Circular smooth muscle and longitudinal smooth muscle.

What is the role of goblet cells in the colon according to the summary notes?

To provide secretions and aid in the absorption process, specifically related to water and Vitamin K.

What structure stores and concentrates bile before releasing it into the duodenum?

The Gall Bladder.