5 - Gastric Motility and Enteric Nervous System (Lecture)

Vocabulary flashcards covering key terms and concepts related to gastric motility, the enteric nervous system, and regulation of gastric emptying from the lecture notes.

Enteric nervous system (ENS)

The network of neurons in the GI tract comprising the myenteric and submucosal plexuses that coordinates GI motility and secretory function.

Myenteric plexus

A component of the ENS located between the circular and longitudinal muscle layers that mainly controls GI motility (tone, rhythm, and propulsion).

Submucosal plexus

A component of the ENS that regulates secretion and absorption in the gut mucosa.

IPANs (Intrinsic Primary Afferent Neurons)

Enteric sensory neurons that detect local changes (stretch, chemicals) and initiate reflexes within the ENS.

Peristalsis

A pattern of GI motility involving coordinated progressive contractions that push contents forward along the tract.

Segmentation

A pattern of GI motility where non-propulsive, rhythmic contractions mix and segment contents for digestion and absorption.

Tonic contraction

Sustained contraction, typically seen in sphincters and some GI regions to maintain tone.

Phasic contraction

Rapid, rhythmic contractions seen in many GI regions that propel contents.

Circular muscle

GI smooth muscle layer arranged around the circumference; participates in constriction and mixing movements.

Longitudinal muscle

GI smooth muscle layer oriented along the length of the tract; helps shorten and shorten/shorten segments during movement.

Smooth muscle

Involuntary muscle type found throughout most of the GIT; organized in circular and longitudinal layers.

Skeletal muscle

Voluntary muscle type found in the pharynx, upper esophagus, and external anal sphincter.

Fundus

Upper stomach region that relaxes to store incoming food during receptive accommodation.

Receptive relaxation

Vago-vagal reflex relaxing the fundus to allow storage of a meal before gastric entry.

Pyloric sphincter

Ring of smooth muscle at the gastric outlet that regulates chyme passage into the duodenum.

Gastric emptying

Process of discharging stomach contents into the duodenum; regulated by neural and hormonal factors.

Cephalic phase

Anticipatory/early phase of digestion triggered by sight, smell, or thought of food; can inhibit or excite gastric activity.

Gastric phase

Phase when food is present in the stomach; gastric processing and emptying begin.

Intestinal phase

Phase when chyme reaches the duodenum; hormones and reflexes modulate gastric emptying and motility.

Secretin

Hormone released in response to low duodenal pH; slows gastric emptying and stimulates bicarbonate secretion.

Cholecystokinin (CCK)

Hormone released in response to fats/proteins; slows gastric emptying and promotes pancreatic enzyme release and bile flow.

Gastrin

Hormone that stimulates gastric acid secretion and can increase motility; released in response to peptides and stomach distension.

GIP (Glucose-dependent Insulinotropic Peptide)

Hormone released with carbohydrates; slows gastric emptying and stimulates insulin release.

Motilin

Hormone that increases GI motility, especially interdigestive migrating motor complexes; promotes contractions during fasting.

Sieve function

Discrimination where liquids and small particles pass more rapidly than large particles during propulsion.

Propulsion

Movement of luminal contents toward the pylorus, aided by contractions and pyloric occlusion.

Grinding

Churning near the antrum to reduce particle size; only particles smaller than about 2 mm pass to the duodenum.

Retropulsion

Backward propulsion returning contents to the stomach body for further grinding and pulverization.

Ileogastric reflex

Reflex where chyme entering the ileum delays gastric emptying via enteric nerves.

Gastric storage (gastric accommodation)

Storage of food in the stomach via fundal relaxation prior to grinding and emptying.

Gastroparesis

Delayed gastric emptying without mechanical obstruction; commonly linked to diabetes and presenting with fullness, nausea, and pain.