Questions and Answers
What segments of the spinal cord do the sacral parasympathetics originate from?
Which of the following statements about sympathetic stimulation of the gastrointestinal tract is true?
Where do most of the postganglionic sympathetic neuron bodies for the gastrointestinal tract reside?
Which neurotransmitter is mainly associated with sympathetic nerve endings in the gastrointestinal tract?
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What primarily initiates intestinal peristalsis?
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What role does the myenteric plexus play in peristalsis?
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What type of fibers supply the sigmoidal, rectal, and anal regions with better parasympathetic supply compared to other intestinal areas?
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Which of the following can inhibit peristalsis?
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Which of the following is NOT a stimulus for the afferent sensory nerve fibers from the gut?
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Which of the following statements about mixing movements in the gastrointestinal tract is true?
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Which segments of the spinal cord are involved in sympathetic innervation of the gastrointestinal tract?
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What type of contractions primarily aid in the mixing of contents within the gut wall?
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What effect do signals transmitted through afferent sensory nerve fibers typically have on intestinal activities?
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What happens when there is a congenital absence of the myenteric plexus?
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What stimulus other than gut distention can initiate peristalsis?
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What effect does strong parasympathetic nervous signaling have on the gut?
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What is the primary trigger for the secretion of gastric inhibitory peptide?
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What is the main function of motilin in the gastrointestinal tract?
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Which movement type primarily facilitates the forward movement of food in the gastrointestinal tract?
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How often do the interdigestive myoelectric complexes occur in a fasting person?
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What explains the mechanism by which peristalsis occurs in the gastrointestinal tract?
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What happens to motilin secretion after food ingestion?
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Which of the following is NOT a functional type of movement in the gastrointestinal tract?
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What role do mixing movements play in the gastrointestinal tract?
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What is the primary role of the myenteric plexus in the enteric nervous system?
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How many neurons approximately compose the enteric nervous system?
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What is the main function of the submucosal plexus?
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Which type of fibers enhance or inhibit gastrointestinal functions through the enteric nervous system?
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Where do sensory nerve endings in the gastrointestinal tract send their afferent fibers?
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What anatomical feature does the myenteric plexus lie between?
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What is the potential effect of the enteric nervous system functioning independently of extrinsic nerves?
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Which statement correctly describes the relationship between the enteric nervous system and extrinsic nerves?
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What is the primary role of the myenteric plexus in the gastrointestinal tract?
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Which of the following effects is NOT associated with the stimulation of the myenteric plexus?
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What type of neurotransmitter is released by some inhibitory neurons within the myenteric plexus?
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The submucosal plexus is primarily concerned with which of the following functions?
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Which muscle layer does the myenteric plexus lie between in the gastrointestinal tract?
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The myenteric plexus is involved in which of the following processes?
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What is the effect of inhibitory signals from the myenteric plexus on intestinal sphincter muscles?
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How does the myenteric plexus affect the tone of the gut wall when stimulated?
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Study Notes
Enteric Nervous System Overview
- The enteric nervous system extends from the esophagus to the anus, containing approximately 100 million neurons, comparable to the entire spinal cord.
- Comprised of two main plexuses:
- Myenteric Plexus (Auerbach’s Plexus): Located between longitudinal and circular muscle layers, primarily controls gastrointestinal movements.
- Submucosal Plexus (Meissner’s Plexus): Positioned in the submucosa, mainly regulates secretion and local blood flow.
Functional Roles of Plexuses
-
Myenteric Plexus:
- Increases gut wall tone, rhythmical contractions, and conduction velocity of excitatory waves.
- Contains excitatory and inhibitory neurons; inhibitory signals help relax intestinal sphincters.
-
Submucosal Plexus:
- Regulates function within minute segments of the intestine, involved mainly in local activities like secretion.
Nervous System Interactions
- Extrinsic sympathetic and parasympathetic fibers connect to both plexuses, enhancing or inhibiting gastrointestinal activity.
- Afferent sensory nerve fibers send signals to the enteric system and higher centers (e.g., spinal cord, brain stem), contributing to local reflexes and overall gut reflex actions.
Sympathetic and Parasympathetic Functions
- Parasympathetic Fibers: Originate from sacral spinal segments, particularly abundant in the rectal area, involved in defecation reflexes.
- Sympathetic Fibers: Originate from the spinal cord (T5-L2) and inhibit gastrointestinal activity, with norepinephrine as the primary neurotransmitter.
Sensory Nerve Functionality
- Sensory nerve fibers respond to gut mucosa irritation, excessive distention, and certain chemicals, leading to excitation/inhibition of intestinal activity.
Hormonal Influences
- Gastric Inhibitory Peptide: Secreted from the upper small intestine in response to fats and amino acids, slows gastric emptying if the intestine is overloaded.
- Motilin: Released from the upper duodenum during fasting, stimulates gastrointestinal motility with cyclic release every 90 minutes.
Types of Gut Movements
- Two primary movement types:
- Propulsive Movements: Move food through the tract (e.g., peristalsis).
- Mixing Movements: Ensure thorough mixing of intestinal contents.
Peristalsis Mechanism
- Involves a contractile ring that moves forward, moving material ahead. Triggered by gut distention and can be influenced by chemical and physical stimuli.
- Requires a functional myenteric plexus; absence severely depresses peristalsis.
Mixing Movements Characteristics
- Vary across the gastrointestinal tract; peristaltic contractions may cause mixing when forward movement is obstructed.
- Local constrictive contractions chop and shear contents, enhancing digestion and absorption efficiency.
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Description
Explore the complexities of the enteric nervous system, which plays a crucial role in the gastrointestinal tract. This quiz will cover its structure, neurons, and primary functions from the esophagus to the anus. Test your knowledge on this vital aspect of human physiology.
