Parasympathetic Supply to the Gut
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Questions and Answers

What is the primary mechanism by which water is absorbed in the small intestine?

  • Simple diffusion
  • Facilitated diffusion
  • Active transport
  • Osmosis (correct)

    • Which enzyme is specifically responsible for splitting lactose into glucose and galactose?

  • Maltase
  • Lactase (correct)
  • Sucrase
  • Alpha-dextrinase

    • What is the purpose of the peristaltic rush in the small intestine?

  • To expel irritative chyme and relieve distention (correct)
  • To promote secretion of digestive enzymes
  • To enhance nutrient absorption
  • To move chyme slowly for better digestion

    • Which method is used for the absorption of fructose in the small intestine?

    <p>Facilitated diffusion</p> Signup and view all the answers

    Which statement correctly describes the absorption of sodium in the small intestine?

    <p>Sodium absorption involves both active transport and diffusion</p> Signup and view all the answers

    What type of secretion do the parotid glands produce?

    <p>Only serous</p> Signup and view all the answers

    Which ion is found in larger quantities in saliva compared to others?

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

    What is the primary digestive function of ptyalin in saliva?

    <p>Splits starch into maltose</p> Signup and view all the answers

    What substance in saliva helps to maintain oral hygiene?

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

    During which stage of swallowing does voluntary control occur?

    <p>Voluntary stage</p> Signup and view all the answers

    What muscle action is primarily engaged by the jaw muscles during chewing?

    <p>Clenching with a force of 55 pounds</p> Signup and view all the answers

    What defines the pharyngeal stage of swallowing?

    <p>Involuntary movement into the esophagus</p> Signup and view all the answers

    What type of peristalsis is primarily involved in the initial movement of food through the esophagus?

    <p>Primary peristalsis</p> Signup and view all the answers

    Which enzyme is responsible for the digestion of fats after emulsification?

    <p>Pancreatic Lipase</p> Signup and view all the answers

    What is the primary role of the ileocecal valve within the digestive system?

    <p>To prevent backflow of fecal contents into the small intestine</p> Signup and view all the answers

    Which of the following compounds are primarily produced in the large intestine?

    <p>Vitamins K and B</p> Signup and view all the answers

    What type of reflex is involved in the intrinsic defecation process?

    <p>Enteric Reflex</p> Signup and view all the answers

    Through which mechanism are dipeptides and tripeptides absorbed in the digestive system?

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

    Mass movements in the colon are characterized by which of the following?

    <p>Constrictive rings at distended points</p> Signup and view all the answers

    What is the primary function of the upper part of the colon?

    <p>Absorption of water and electrolytes</p> Signup and view all the answers

    Which digestive enzyme acts on disaccharides in the intestine to produce simpler sugars?

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

    Which cranial nerve provides parasympathetic innervation to the gut?

    <p>Vagus nerve</p> Signup and view all the answers

    What is the frequency of slow waves in the duodenum?

    <p>12/min</p> Signup and view all the answers

    Which of the following is NOT a functional type of movement in the gastrointestinal tract?

    <p>Respiratory movement</p> Signup and view all the answers

    What initiates spike potentials in gastrointestinal smooth muscle?

    <p>Rising membrane potential above -40 mV</p> Signup and view all the answers

    Which part of the gastrointestinal tract has the highest frequency of slow waves?

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

    What primarily stimulates the gastrointestinal tract's mixing movements?

    <p>Peristaltic contractions</p> Signup and view all the answers

    The law of the gut states that ingestion of food is primarily determined by which intrinsic desire?

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

    Which glands are principal in the secretion of saliva?

    <p>Parotid, Submandibular, and Sublingual glands</p> Signup and view all the answers

    What is the primary consequence of damage to the cranial nerves involved in the swallowing mechanism?

    <p>Inability to swallow food</p> Signup and view all the answers

    Which condition is characterized by the failure of the lower esophageal sphincter to relax during swallowing?

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

    What is a common symptom of appendicitis?

    <p>Referred pain to the mid-abdomen</p> Signup and view all the answers

    Which of the following is NOT typically a cause of peptic ulcers?

    <p>Excessive dietary fiber</p> Signup and view all the answers

    What causes gastritis?

    <p>Injury or damage to gastric mucosa</p> Signup and view all the answers

    In which condition would you expect to find achlorhydria?

    <p>Gastric atrophy</p> Signup and view all the answers

    What type of cell in the small intestine is responsible for the absorption of water and electrolytes?

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

    Which of the following is a symptom of failure of the glottis to close during swallowing?

    <p>Food passage into the lungs</p> Signup and view all the answers

    Study Notes

    Parasympathetic and Sympathetic Nervous Supply to the Gut

    • Cranial supply comes from the Vagus nerve (10th cranial), providing innervation to the esophagus, stomach, pancreas, and first half of the large intestine.
    • Sacral supply originates from the 2nd, 3rd, and 4th spinal pelvic nerves, helping execute defecation reflexes.
    • Parasympathetic stimulation increases the overall activity of the enteric nervous system.
    • Sympathetic fibers arise from T5 to L2 spinal cord segments and inhibit gastrointestinal (GIT) activity.

    Electrical Activity of GIT Smooth Muscle

    • Slow Waves (Basic Electrical Rhythm - BER):
      • Generated by Na-K pump activity; frequency differs in GIT regions:
        • 3/min in stomach
        • 12/min in duodenum
        • 8-9/min in terminal ileum
    • Spike Potentials:
      • True action potentials occurring when resting membrane potential exceeds -40 mV; triggered by slow Ca-Na channel opening, leading to muscle contraction and peristalsis.

    Functional Types of Movement in the GIT

    • Mixing Movements: GIT continuously mixes contents by peristaltic or local constrictive contractions.
    • Propulsive Movement: Advances food through the digestive tract.
    • Peristalsis: Key propulsive movement stimulated by the myenteric plexus, irritants, or extrinsic nervous signals.

    Law of the Gut

    • Ingestion driven by hunger (intrinsic desire) and appetite (food preference).
    • Saliva, rich in amylase (ptyalin), begins starch digestion upon food entry in the mouth.

    Secretion of Saliva

    • Major glands: Parotid, Submandibular, and Sublingual; small Buccal glands also present.
    • Saliva contains two primary proteins:
      • Serous Secretion: Contains ptyalin for starch digestion.
      • Mucous Secretion: Contains mucin for lubrication.
    • Saliva composition: high in potassium and bicarbonate, low in sodium and chloride.

    Functions of Saliva

    • Mechanical Functions: Moistens mouth, aids in speech and mastication, and protects mucous membranes.
    • Digestive Functions: Ptyalin breaks down starch into maltose.
    • Excretory Functions: Eliminates urea, heavy metals, and other substances.
    • Oral Hygiene: Washes away bacteria and food particles, contains bactericidal thiocyanate and enzymes.

    Mastication and Swallowing (Deglutition)

    • Mastication: Utilizes molars for grinding, incisors for cutting; muscles exert about 55 pounds of force.
    • Swallowing Stages:
      • Voluntary Stage: Initiates swallowing.
      • Pharyngeal Stage: Involuntary; involves nasopharynx, oropharynx, and laryngopharynx; regulated by pharyngoesophageal sphincter.
      • Esophageal Stage: Promotes food passage using primary and secondary peristalsis.

    Peristaltic Rush

    • Rapid peristalsis in the small intestine due to mucosal irritation, aiming to expel irritative chyme and reduce distension.
    • Triggered by autonomic nervous reflexes and intrinsic myenteric reflexes.

    Enzymes in Small Intestinal Secretions

    • Secreted by epithelial cells in the intestinal mucosa, crucial for nutrient absorption:
      • Enterokinase activates proteolytic enzymes: Aminopolypeptidase, Dipeptides.
      • Carbohydrate Enzymes: Lactase, Sucrase, Maltase, Alpha-dextrinase.

    Absorption in the GIT

    • Water Absorption: 99% occurs by osmosis.
    • Sodium: Absorbed (25-35 gm/day) through active transport and diffusion.
    • Ion Absorption: Active transport for Ca, Fe; Na-glucose co-transport for glucose and galactose; facilitated diffusion for fructose.
    • Protein Absorption: Amino acids via sodium-cotransport and larger peptides by pinocytosis.

    Digestion of Nutrients

    • Starches: Broken down by enzymes from saliva and pancreatic amylase.
    • Fats: Emulsified by bile and digested by pancreatic lipase.
    • Proteins: Protein digestion initiated by pepsin, followed by trypsin, chymotrypsin, and carboxypeptidase.

    Ileocecal Valve

    • Prevents retrograde flow of fecal matter from the colon into the small intestine; withstands reverse pressures of 50-60 cm H2O.

    Functions and Movements of the Colon

    • Absorbs water and electrolytes, forming feces in the upper part; stores fecal matter in the lower part.
    • Movements classified as:
      • Mixing movements (Haustration)
      • Propulsive movements (Mass Movements) that occur during distension or irritation.

    Defecation

    • Internal Anal Sphincter: Involuntary control, smooth muscle.
    • External Anal Sphincter: Voluntary control, striated muscle.
    • Types of defecation reflex include intrinsic reflexes and those influenced by the autonomic nervous system.

    GIT Pathophysiology

    • Dysphagia Causes: Damage to cranial nerves, neurological disorders, or muscular atrophy affecting swallowing.
    • Gastritis: Inflammation of gastric mucosa from various irritants.
    • Peptic Ulcer: Excoriations in mucosa due to excess gastric acid and stress factors.
    • Appendicitis: Infection-causing inflammation; symptoms include abdominal pain and intestinal obstruction.

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    Description

    Explore the division of the parasympathetic supply to the gut, focusing on the roles of the cranial and sacral components. This quiz covers the vagus nerve's influence and its extensive innervation across the digestive system, including reflex actions. Understand how these fibers enhance the overall activity of the enteric nervous system.

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