Control of the GI Tract Quiz
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Control of the GI Tract Quiz

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Questions and Answers

What is the primary function of the stomach in relation to ingested food?

  • Breaking down food through enzymatic action
  • Short-term storage of ingested food (correct)
  • Absorption of nutrients
  • Production of digestive enzymes

    • Which nerve pathways are involved in the process of receptive relaxation of the stomach?

  • Sympathetic nervous system pathways
  • Vagus nerve pathways (correct)
  • Peripheral nervous system pathways
  • Spinal cord pathways

    • What role does nitric oxide (NO) play in gastric motor function?

  • Stimulates gastric acid secretion
  • Facilitates muscle contraction
  • Inhibits food mixing
  • Promotes relaxation of stomach muscles (correct)

    • Which statement correctly describes gastric accommodation?

    <p>It allows for increased volume without pressure increase.</p> Signup and view all the answers

    What is the function of the pyloric sphincter in gastric motor activity?

    <p>Regulates emptying of stomach contents into the intestines</p> Signup and view all the answers

    What is the primary function of the vagal afferents in the gastrointestinal tract?

    <p>To relay information from receptors to higher centers</p> Signup and view all the answers

    Which part of the gastrointestinal tract has the fastest smooth muscle slow waves?

    <p>Duodenum</p> Signup and view all the answers

    What type of reflexes result from the intrinsic control of the gastrointestinal tract?

    <p>Short or intrinsic reflexes</p> Signup and view all the answers

    What role do Interstitial Cells of Cajal play in smooth muscle activity?

    <p>They trigger waves of smooth muscle contraction</p> Signup and view all the answers

    How often do smooth muscle slow waves occur in the stomach?

    <p>Every 20 seconds</p> Signup and view all the answers

    Which type of cells are responsible for gastric acid secretion?

    <p>Parietal or oxyntic cells</p> Signup and view all the answers

    What type of innervation do postganglionic efferent fibers provide in the enteric system?

    <p>To blood vessels and secretory cells</p> Signup and view all the answers

    What kind of activity occurs due to cycles of depolarization in smooth muscle?

    <p>Contraction cycles without reaching threshold</p> Signup and view all the answers

    What role do motor neurons play in the enteric nervous system?

    <p>Control motility and secretions</p> Signup and view all the answers

    What is the primary function of the Meissner’s Plexus?

    <p>Control secretion of the mucosa</p> Signup and view all the answers

    Which neurotransmitter is primarily used by the sympathetic nervous system to decrease motility and secretions?

    <p>Noradrenaline (NA)</p> Signup and view all the answers

    What describes the main function of the autonomic nervous system in relation to the GI tract?

    <p>To control involuntary actions and responses</p> Signup and view all the answers

    Which structure of the enteric nervous system is located between the longitudinal and circular smooth muscle layers?

    <p>Plexus of Auerbach</p> Signup and view all the answers

    Which statement is true about the intrinsic control of the GI tract?

    <p>It includes the enteric nervous system's control mechanisms</p> Signup and view all the answers

    How does the parasympathetic nervous system affect gastrointestinal contractions?

    <p>Increases contractions and enhances secretions</p> Signup and view all the answers

    What type of neurons convey information regarding muscle stretch and chemical composition from the mucosa?

    <p>Sensory neurons</p> Signup and view all the answers

    What initiates stomach contractions during the cephalic phase?

    <p>Thinking or seeing food</p> Signup and view all the answers

    Which hormone is responsible for increasing the number and force of stomach contractions?

    <p>Gastrin</p> Signup and view all the answers

    What role do mechanical stimuli play in gastric contractions?

    <p>They initiate peristaltic contractions</p> Signup and view all the answers

    How does the composition of food entering the duodenum affect gastric motility?

    <p>It activates receptors that lead to hormone release</p> Signup and view all the answers

    What characterizes the emptying process from the stomach to the duodenum?

    <p>Coordinated contractions facilitate emptying</p> Signup and view all the answers

    What happens to pressure in the stomach as volume increases?

    <p>Pressure remains constant with increasing volume</p> Signup and view all the answers

    Where does the contraction process start in the stomach?

    <p>In the mid-stomach</p> Signup and view all the answers

    How does the force of contractions change as they approach the pyloric sphincter?

    <p>The force increases</p> Signup and view all the answers

    What is the result of contractions overtaking the stomach contents?

    <p>Food is pushed back for mixing</p> Signup and view all the answers

    What occurs during the fasted state of the stomach?

    <p>The stomach is quiescent</p> Signup and view all the answers

    Which region of the stomach is referred to as the pacemaker region?

    <p>Proximal stomach</p> Signup and view all the answers

    What is the role of the pyloric sphincter in the stomach?

    <p>Regulates the emptying of food into the duodenum</p> Signup and view all the answers

    Which of the following best describes the contractions moving towards the pyloric region?

    <p>They increase in force and speed</p> Signup and view all the answers

    Study Notes

    Control of the GI Tract

    • Control of the gastrointestinal (GI) tract is managed through neural and humoral factors.
    • Intrinsic control is governed by the enteric nervous system (ENS), while extrinsic control involves the autonomic nervous system (ANS).
    • GI hormones play a role in both intrinsic and extrinsic control.

    Enteric Nervous System (ENS)

    • The ENS consists entirely of neurons within the GI tract.
    • Comprises three types of neurons: sensory neurons (detecting stretch and chemical content), motor neurons (controlling motility and secretions), and inter-neurons (relaying information between sensory and motor neurons).
    • Arranged in two main plexuses:
      • Myenteric (Auerbach's) Plexus: located between circular and longitudinal smooth muscle, regulates motor function.
      • Submucosal (Meissner’s) Plexus: regulates mucosal secretion.

    Extrinsic Control of the GI Tract

    • Controlled by the autonomic nervous system.
    • Parasympathetic Nervous System:
      • Vagus nerve and pelvic nerve innervate plexuses, enhancing gastric contractions and secretions via acetylcholine (ACh).
      • Acts as "rest and digest," providing sensory feedback.
    • Sympathetic Nervous System:
      • Originates from prevertebral ganglia, reducing motility and secretions primarily through noradrenaline.

    Smooth Muscle Slow Waves

    • Initiated by Interstitial Cells of Cajal located between smooth muscle layers.
    • Waves of contraction depend on cycles of depolarization that may require additional stimulation from the ANS or hormones.
    • Frequencies vary:
      • Duodenum: every 4-5 seconds
      • Ileum: every 6-7 seconds
      • Stomach and colon: approximately every 20 seconds.

    Gastric Motor Function

    • The stomach has three main functions:
      • Short-term storage of food.
      • Mixing of gastric contents.
      • Controlled emptying into the intestines.

    Receptive Relaxation

    • Swallowing triggers relaxation of the lower esophagus and proximal stomach via a vagovagal reflex.
    • Allows the stomach to accommodate food volume without a significant rise in pressure, controlled by the enteric nervous system.

    Mixing and Emptying

    • The distal stomach exhibits a spontaneous electrical rhythm similar to the small intestine.
    • Contractions begin mid-stomach and intensify as they reach the pyloric sphincter, facilitating the mixing of contents and gradual emptying.

    Factors Affecting Contractions

    • The stomach is relatively inactive in the fasted state but shows contractions during the cephalic phase (anticipation of food).
    • In the fed state, contractions are continuous, influenced by:
      • Mechanical stimuli (distension).
      • Neurotransmitters like ACh, which enhance contractions.
      • Hormones such as gastrin (increases contractions) and secretin (decreases contractions).

    Emptying

    • Coordinated contractions lead to effective emptying, influenced by the relaxatation of the pylorus and limited contractions in the duodenum.
    • Gastric emptying time depends on food composition:
      • Liquids empty quickly while solids take longer due to the need for size reduction.
    • Food composition activates receptors in the duodenum, prompting hormonal release that adjusts gastric motility.

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    Description

    Test your knowledge on the control mechanisms of the gastrointestinal tract. This quiz covers the intrinsic and extrinsic factors that influence gut function, including the roles of the enteric nervous system and GI hormones. Perfect for students studying human physiology or related fields.

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