5. Gastric Motility
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Questions and Answers

What receptor type is responsible for monitoring gastric volume?

  • Mechanoreceptors (correct)
  • Chemoreceptors
  • Nociceptors
  • Thermoreceptors

    • Which of the following directly stimulates the release of gastrin?

  • Activation of sympathetic neurons
  • Increased gastric emptying
  • Detection of low pH in the duodenum
  • Activation of cholinergic neurons (correct)

    • What is the primary effector response resulting from the activation of visceral afferents and the vagus nerve due to increased gastric volume?

  • Increased gastric acid secretion only
  • Decreased gastric motility
  • Decreased gastric emptying
  • Increased gastric motility and emptying (correct)

    • Which of the following is NOT a stimulus for gastrin release, according to the provided information?

    <p>Detection of lipids in the small intestine (B)</p> Signup and view all the answers

    What is the correct order of the neural pathway involved in the stimulatory control of gastric motility in response to increased gastric volume?

    <p>Mechanoreceptors → Enteric nervous afferents → Interneurons → ENS effectors (A)</p> Signup and view all the answers

    What is the primary neurocrine mediator responsible for cholinergic action during Phase III of gastric motility?

    <p>Motilin (D)</p> Signup and view all the answers

    Which event will interrupt the Migrating Motor Complex (MMC)?

    <p>Ingestion of a meal (C)</p> Signup and view all the answers

    During hunger contractions, what happens after 24-72 hours of an empty stomach?

    <p>Intense rhythmic peristaltic contractions fuse into tetanic contractions (C)</p> Signup and view all the answers

    What is the approximate interval at which phases of gastric motility repeat themselves, as indicated by the migrating motor complex, during fasting?

    <p>2-hour intervals (C)</p> Signup and view all the answers

    How many hours after the stomach empties do hunger contractions typically begin to occur?

    <p>12-24 hours (B)</p> Signup and view all the answers

    What effect does duodenal hypertonicity have on gastric emptying?

    <p>Less gastric emptying (B)</p> Signup and view all the answers

    What duodenal pH level, monitored by mucosal receptors, results in decreased gastric emptying?

    <p>pH &lt; 3.5 - 4.0 (D)</p> Signup and view all the answers

    How does a full duodenum affect gastric emptying, as monitored by stretch receptors?

    <p>Less gastric emptying (A)</p> Signup and view all the answers

    Which of the following mechanisms mediates reduced gastric motility and emptying in the enterogastric reflex?

    <p>Activation of sympathetic efferents (B)</p> Signup and view all the answers

    Cholecystokinin (CCK) is released in the intestinal lumen. Which of the following stimuli causes this release?

    <p>Lipids of 12-18 C atoms (B)</p> Signup and view all the answers

    What is the main effect of GLP-1 on gastric motility?

    <p>Reduce gastric motility (C)</p> Signup and view all the answers

    How do high-fat diets affect the rate of gastric emptying compared to low-fat diets?

    <p>High-fat diets empty slower than low-fat diets (B)</p> Signup and view all the answers

    During the interdigestive period, what is the primary function of migrating motor complexes (MMCs)?

    <p>To clear the stomach and small bowel of indigestible content (A)</p> Signup and view all the answers

    What is the primary motility pattern of the proximal stomach?

    <p>Tonic contractions without peristalsis (D)</p> Signup and view all the answers

    Which of the following is a motor function of the stomach?

    <p>Storage of contents (B)</p> Signup and view all the answers

    What is the primary function of receptive relaxation in the stomach?

    <p>To facilitate the storage of ingested food (B)</p> Signup and view all the answers

    Which event triggers receptive relaxation in the stomach?

    <p>Continuation of esophageal peristalsis (A)</p> Signup and view all the answers

    What is the role of the distal stomach in gastric motility?

    <p>Mixing and grinding of gastric contents and propulsion (C)</p> Signup and view all the answers

    What is acid chyme?

    <p>The liquid of dissolved food + HCl + pepsin in the stomach (B)</p> Signup and view all the answers

    What influences steady pressure towards the antrum of the stomach?

    <p>The stomach being filled (C)</p> Signup and view all the answers

    What is the function of stomach accommodation?

    <p>Tension in the stomach wall can increase significantly without an increase in intragastric pressure (D)</p> Signup and view all the answers

    Flashcards

    Gastric Motility

    The motor functions of the stomach, including reception, storage, mixing, and propulsion of food.

    Proximal Stomach Functions

    Main functions include receiving and storing food through tonic contractions without peristalsis.

    Receptive Relaxation

    A process allowing the stomach to accommodate incoming food without increasing pressure.

    Accommodation

    The ability of the stomach wall to increase tension without a rise in intragastric pressure.

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    Distal Stomach Functions

    Involves peristalsis for propulsion, mixing, and retropulsion of gastric contents.

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    Peristalsis

    A rhythmic contraction pattern that propels food through the digestive tract.

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    Pylorus

    The opening from the stomach into the duodenum, regulated during emptying.

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    Retropulsion

    The backward movement of food in the stomach during mixing, ensuring thorough grinding.

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    Antrum

    Narrow part of the pylorus in the stomach.

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    Stimulatory Control

    Activation of gastric motility in response to food volume.

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    Hormonal Control

    Gastrin increases gastric motility when stimulated.

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    Feedback Control

    Inhibition of gastric motility based on feedback signals.

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    Enterogastric reflex

    Neural activity affecting gastric emptying based on duodenal conditions.

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    Duodenal osmoreceptors

    Mucosal receptors that monitor the osmolality of duodenal contents.

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    Effect of duodenal pH

    Mucosal receptors that respond to the pH of duodenal contents.

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    Stretch receptors (duodenum)

    Receptors that monitor the volume of food in the duodenum.

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    Sympathetic efferents

    Nerve pathways that reduce gastric motility.

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    Cholecystokinin (CCK)

    Hormone released in response to lipids and amino acids that reduces gastric motility.

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    Migrating motor complex (MMC)

    Cyclic pattern of motility that occurs between meals to clear the digestive tract.

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    Phases of MMC

    Three phases of migrating motor complex: Phase I (slow waves), Phase II (spiking), Phase III (peristalsis).

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    Motilin

    A hormone that stimulates cholinergic action in gastric motility during Phase III.

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    Hunger contractions

    Contractions that occur 12 to 24 hours after the stomach empties, intensifying over 24-72 hours.

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    Gastric accommodation

    The ability of the stomach to expand without increasing pressure when food enters.

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    Migrating motor complex

    A pattern of electromechanical activity in the gastrointestinal tract during fasting.

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    Peristaltic contractions

    Rhythmic contractions of the stomach that propel food through the digestive tract.

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    Study Notes

    Gastric Motility

    • Gastric motility is the movement of food through the stomach, applying to both simple and ruminant stomachs.
    • The stomach performs four main tasks:
      • Receives ingested food
      • Stores food
      • Mixes and grinds food
      • Propels food into the duodenum
    • Gastric digestion involves the formation of acid chyme, a mixture of dissolved food, HCl, and pepsin.

    Proximal Stomach Motility

    • Motility pattern is tonic, not phasic.
    • Tonic contractions are dominated by the circular smooth muscle layer.
    • The circular smooth muscles relax during meals to allow storage.
    • As the stomach empties, the inhibitory neurons turn off, the circular SM proximal starts contracting, forcing the content distally.

    Distal Stomach Motility

    • Basic motility is peristalsis, driven by a pacemaker in the mid-region of the stomach.
    • Functions include propulsion of contents through the antrum and emptying via the pylorus, mixing and grinding of gastric contents, and retropulsion of solid matter.

    Gastric Emptying

    • Empties faster with liquids compared to solids.
    • Low-fat diets empty faster compared to high-fat diets.
    • Gastric emptying is controlled by both neural and hormonal mechanisms.

    Neural Control

    • Mechanoreceptors monitor gastric volume and chemoreceptors detect amino acids, pH, and osmolarity.
    • These signals activate enteric nervous afferents, then interneurons activating ENS effectors and visceral afferents to the CNS/vagus parasympathetic, affecting ENS effectors.
    • This leads to increased gastric motility and emptying.

    Hormonal Control

    • Gastrin is stimulated by filling (amino acids, dietary, acid hydrolysis, pepsin).
    • Gastrin increases gastric motility and emptying via action on smooth muscle.
    • Other hormones such as CCK and GLP-1 regulate gastric motility.

    Feedback Control

    • Feedback mechanisms, primarily through the duodenum, inhibit gastric emptying.
    • Duodenal receptors respond to osmolality, pH, and stretch.
    • Reduced gastric motility/emptying is achieved by activation of sympathetic efferents and deactivation of parasympathetic efferents, or hormonal factors.
    • Hormones like Cholecystokinin (CCK) slow gastric emptying, while Gastric Inhibitory Peptide (GIP) might affect it.

    Migrating Motor Complex (MMC)

    • MMCs are interdigestive periods (between meals), where the stomach and small bowel are cleared of indigestible content.
    • MMCs consist of phases, featuring slow waves followed by peristaltic contractions.
    • Interdigestive motor patterns are mediated by a CNS timing mechanism, involving MMCs that help empty the gut.
    • Motilin provides neurocrine function in Phase III, driving peristaltic contractions, and maintaining the pylorus open to clear the stomach.

    Hunger Contractions

    • Occur 12-24 hours post-eating without food intake.
    • Increased intensity of MMCs (Migrating Motor Complexes).
    • Intense rhythmic peristaltic contractions fuse into tetanic spasms, causing hunger pangs.

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    Gastric Motility PDF

    Description

    Explore the fundamentals of gastric motility, including the movement of food through both simple and ruminant stomachs. This quiz covers key tasks of the stomach, motility patterns, and the mechanisms of gastric digestion, including the formation of acid chyme.

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