GI Physiology

Questions and Answers

Which of the following is NOT a gastrointestinal hormone that adheres to the criteria mentioned in the text?

Gastrin

Motilin

Glucagon (correct)

Secretin

What is the primary role of Interstitial Cells of Cajal (ICC) in the gastrointestinal tract?

Secrete digestive enzymes

Sense luminal contents

Act as pacemakers for muscle contractions (correct)

Produce hormones like gastrin

How do slow waves in the gastrointestinal tract differ from action potentials?

Slow waves are electrical impulses that travel long distances in the gut.

Slow waves are chemical signals that are released by enteroendocrine cells.

Slow waves are slower and do not directly cause muscle contraction. (correct)

Slow waves are faster and cause muscle contraction directly.

What is the role of the myenteric plexus in peristalsis?

It coordinates muscle contractions to propel food through the gut. Signup and view all the answers

Which of the following is NOT a factor that can stimulate slow waves in the gastrointestinal tract?

Release of hormones like gastrin Signup and view all the answers

What is the primary function of the gastro-colic reflex?

It increases motility in the colon and triggers defecation. Signup and view all the answers

Which of the following gastrointestinal disorders is primarily characterized by slow wave abnormalities?

Gastroparesis Signup and view all the answers

Which of the following statements accurately describes the role of taste buds in digestion?

Taste buds stimulate the production of saliva, which aids in digestion. Signup and view all the answers

What is the main function of the tenia coli in the large intestine?

To create the characteristic sacculations (haustra) of the colon Signup and view all the answers

Which of the following is NOT a region of the large intestine?

Jejunum Signup and view all the answers

What is the primary role of goblet cells in the large intestine?

Secretion of mucus Signup and view all the answers

Which type of motility in the large intestine is responsible for propelling the contents towards the rectum for defecation?

Mass movements Signup and view all the answers

What is the primary function of the caecum?

Compressing material into faecal matter Signup and view all the answers

What is the most common cause of lactose intolerance?

Deficiency in lactase enzyme Signup and view all the answers

Which of the following is a characteristic of the gastro-colic reflex?

It is stimulated by the presence of food in the stomach Signup and view all the answers

Which of the following is a condition that can lead to malabsorption?

Coeliac disease Signup and view all the answers

What is the primary function of the colon in relation to material retention?

Water reabsorption and fermentation Signup and view all the answers

Which of the following describes a characteristic of mass movements in the colon?

Propels feces toward the rectum 2-3 times per day Signup and view all the answers

What is the condition called where part of the colon has no innervation, leading to dilated segments?

Hirschsprung's disease Signup and view all the answers

What is a significant consequence of having an aganglionic segment in Hirschsprung's disease?

Toxic megacolon due to stricture Signup and view all the answers

Which of the following describes the gastro-colic response?

It triggers mass movements in the colon after eating. Signup and view all the answers

What primarily characterizes the mixing of contents in the colon?

Segmented contractions for effective mixing Signup and view all the answers

Study Notes

Gastrointestinal Motility and Hormonal Control

Segmented contractions in the colon occur 99% of the time, retaining material for water reabsorption and fermentation, and mixing contents.
Mass movement of material into the aboral end of the colon occurs 2-3 times a day, propelled by the gastro-colic response.

Hirschsprung's Disease and Toxic Mega Colon

Hirschsprung's disease is a congenital disorder where all or part of the colon has no innervation, resulting in a strictured aganglionic segment and a dilated proximal segment.

Hormonal Control of the GI Tract

There are over 22 hormones and paracrines secreted by Enteroendocrine cells (EEC) in the mucosa, which sense luminal contents and release hormones and paracrines.
Five main gastrointestinal hormones are: Gastrin, Cholecytokinin (CCK), Secretin, Glucose-dependent Insulinotrophic peptide (GIP), and Motilin.

Motility in the GI Tract

Phasic contractions in the small intestine include peristalsis (waves of contractions, 20cm) and segmented contractions (10cm).
Tonic contractions are long-lasting contractions that close sphincters, controlling movement of material through the tract and maintaining an ordered sequence of events.

Peristalsis

Peristalsis is the propulsion of material through the GI tract, mediated by neurones in the myenteric plexus and Interstitial Cells of Cajal (ICC).
ICCs are pacemakers of the gut, producing slow waves that differ in different regions of the GI tract.

Slow Waves

Slow waves are slow undulating changes in resting membrane potential, not action potentials, which don't cause contraction until the threshold (-40mV) is reached.
Slow waves are activated by distention (bolus of food) stimulating stretch receptors and parasympathetic nerves (ACh).

The Large Intestine

The large intestine is 1.5m long, thicker than the small intestine, and consists of the caecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anus.
The large intestine has tenia coli (3 bands of longitudinal muscle), sacculations, no villi, and a high concentration of goblet cells for mucus secretion.

Motility in the Large Intestine

Slow movement of contents in the large intestine involves segmented contractions to retain material for water reabsorption and fermentation, and mass movements 2-3 times a day to move material into the aboral end of the colon for defecation.
Pacemakers of the gut produce slow waves that couple to motility, with different subtypes in the large intestine.

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Description

This quiz covers the processes of gastrointestinal motility, including segmented contractions and mass movement, as well as disorders like Hirschsprung's disease and toxic mega colon.