Physiology of Gastric Secretion
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Questions and Answers

What is the primary stimulus for gastric secretion during the cephalic phase?

  • Gastrin release
  • Somatostatin release
  • Stretch receptors
  • Vagal input (correct)

    • What is the primary function of bile in the body?

  • To dispose of cholesterol (correct)
  • To regulate blood sugar levels
  • To aid in protein synthesis
  • To produce energy for the body

    • What is the main component of bile that facilitates digestion?

  • Bile acids (correct)
  • Glucuronides
  • Bile pigments
  • Electrolyte solution

    • What is the function of the proton pump in gastric parietal cells?

    <p>To move H+ ions out of the parietal cell against a concentration gradient</p> Signup and view all the answers

    How much bile is secreted by the liver per day?

    <p>500 mL</p> Signup and view all the answers

    What is the role of somatostatin in gastric secretion?

    <p>To inhibit G and ECL cells</p> Signup and view all the answers

    What is the consequence of the release of equivalent numbers of bicarbonate ions into the bloodstream during gastric secretion?

    <p>It neutralizes gastric acidity once its function is complete</p> Signup and view all the answers

    What is the process by which bile components are reabsorbed in the intestine and excreted again by the liver?

    <p>Enterohepatic circulation</p> Signup and view all the answers

    What is responsible for the yellow color of bile?

    <p>Glucuronides of bilirubin and biliverdin</p> Signup and view all the answers

    What is the primary function of the enzymes present in pancreatic juice?

    <p>To facilitate digestion</p> Signup and view all the answers

    What is the primary means of gastrointestinal regulation?

    <p>Endocrine regulation</p> Signup and view all the answers

    What is the mechanism by which gastric secretion is terminated after the meal moves into the small intestine?

    <p>The buffering of gastric acidity by the meal</p> Signup and view all the answers

    What is the daily secretion volume of pancreatic juice?

    <p>1500 mL</p> Signup and view all the answers

    What is the primary mechanism controlling the secretion of pancreatic juice?

    <p>Hormonal control</p> Signup and view all the answers

    What is the purpose of trypsin inhibitor secreted by the pancreas?

    <p>To inhibit trypsin</p> Signup and view all the answers

    What is the pH range of the duodenal contents after pancreatic juice secretion?

    <p>6.0-7.0</p> Signup and view all the answers

    What is the role of bile acids in the digestive process?

    <p>Digestion and absorption of fats</p> Signup and view all the answers

    What is the form in which most digestive enzymes are released from the pancreas?

    <p>Inactive form</p> Signup and view all the answers

    What is the name of the polypeptide that stimulates insulin secretion when administered at blood levels comparable to those produced by oral glucose?

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

    What is the primary function of the myenteric plexus?

    <p>Motor control of the longitudinal and circular smooth muscle layers</p> Signup and view all the answers

    What is the main effect of Motilin on the stomach and intestines?

    <p>Contraction of smooth muscle</p> Signup and view all the answers

    What is the role of ghrelin in the body?

    <p>Stimulating growth hormone secretion and food intake</p> Signup and view all the answers

    What is the main effect of Somatostatin on the gastrointestinal system?

    <p>Inhibition of gastrin secretion</p> Signup and view all the answers

    What is the main stimulant of GIP secretion?

    <p>Glucose and fat in the duodenum</p> Signup and view all the answers

    What is the estimated number of neurons in the enteric nervous system in humans?

    <p>100 million</p> Signup and view all the answers

    What is the name of the plexus located between the middle circular layer and the mucosa?

    <p>Meissner plexus</p> Signup and view all the answers

    What is the name of the hormone that inhibits gastric secretion and motility?

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

    What is the function of substance P in the gastrointestinal tract?

    <p>Increasing the motility of the small intestine</p> Signup and view all the answers

    What is the name of the cells that secrete Motilin?

    <p>Enterochromaffin cells (EC) and Mo cells</p> Signup and view all the answers

    What is the term used to describe the enteric nervous system?

    <p>The little brain</p> Signup and view all the answers

    What is the primary route by which the body disposes of cholesterol?

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

    What is the term used to describe the circulation of bile components in the body?

    <p>Enterohepatic circulation</p> Signup and view all the answers

    What is the component of bile responsible for its golden yellow color?

    <p>Bile pigments</p> Signup and view all the answers

    What is the primary function of the bile acids in the digestive process?

    <p>To facilitate digestion</p> Signup and view all the answers

    What is the daily volume of bile secretion by the liver?

    <p>500 mL</p> Signup and view all the answers

    What is the primary mechanism of gastrointestinal regulation?

    <p>Endocrine regulation</p> Signup and view all the answers

    What is the primary purpose of gastric secretion in the stomach?

    <p>To sterilize the meal and initiate hydrolysis of macromolecules</p> Signup and view all the answers

    What is the role of intrinsic factor in the stomach?

    <p>To enhance the absorption of vitamin B12</p> Signup and view all the answers

    What type of cells in the stomach produce pepsinogens and gastric lipase?

    <p>Chief cells</p> Signup and view all the answers

    What neurotransmitter triggers the release of gastrin from G cells in the stomach?

    <p>Gastrin-releasing peptide (GRP)</p> Signup and view all the answers

    What is the daily volume of gastric secretion in the stomach?

    <p>2.5 L/day</p> Signup and view all the answers

    What is the primary function of mucus and bicarbonate secretion by surface cells in the stomach?

    <p>To protect the stomach from self-digestion</p> Signup and view all the answers

    What is the primary component of saliva that helps to neutralize gastric secretions that reflux into the esophagus?

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

    Which branch of the autonomic nervous system plays the most prominent role in controlling salivary secretion?

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

    What is the primary function of saliva in relation to taste?

    <p>To stimulate the taste buds</p> Signup and view all the answers

    What is the name of the phase of gastric secretion that occurs before food is ingested?

    <p>Cephalic phase</p> Signup and view all the answers

    What is the primary function of saliva in relation to mouth cleanliness?

    <p>To keep the mouth and teeth clean</p> Signup and view all the answers

    What is the primary purpose of the stomach in the digestive process?

    <p>To mix food with digestive juices</p> Signup and view all the answers

    What is the primary mechanism by which CCK secretion is controlled?

    <p>Positive feedback loop involving the stimulation of protein and fat digestion</p> Signup and view all the answers

    What is the primary function of secretin in the digestive process?

    <p>To increase the secretion of bicarbonate-rich pancreatic juice and neutralize acid</p> Signup and view all the answers

    What is the stimulus for the secretion of secretin?

    <p>The presence of acid in the duodenum</p> Signup and view all the answers

    What is the effect of secretin on gastric acid secretion?

    <p>It inhibits the secretion of gastric acid</p> Signup and view all the answers

    What is the primary mechanism by which somatostatin inhibits gastrin secretion?

    <p>By acting in a paracrine fashion</p> Signup and view all the answers

    What is the effect of GIP on gastric secretion and motility?

    <p>It inhibits gastric secretion and motility</p> Signup and view all the answers

    What is the primary site of secretion of Gastric Inhibitory Peptide (GIP)?

    <p>Mucosa of the duodenum and jejunum</p> Signup and view all the answers

    Which of the following hormones is secreted by enterochromaffin cells (EC) and Mo cells in the stomach, small intestine, and colon?

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

    What is the effect of secretin on pancreatic secretion?

    <p>It increases the secretion of bicarbonate-rich pancreatic juice</p> Signup and view all the answers

    What is the stimulus for the secretion of somatostatin in the gastrointestinal mucosa?

    <p>Acid in the lumen</p> Signup and view all the answers

    What is the effect of motilin on the stomach and intestines?

    <p>It contracts smooth muscle</p> Signup and view all the answers

    What is the unique property of GIP that distinguishes it from other hormones that stimulate insulin secretion?

    <p>It stimulates insulin secretion when administered at blood levels comparable to those produced by oral glucose</p> Signup and view all the answers

    What is the primary function of the gastrointestinal tract?

    <p>To absorb nutrients and water into the body</p> Signup and view all the answers

    What is the first secretion encountered when food is ingested?

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

    What is the location of the glandular structures that deliver secretions into the lumen of the intestine?

    <p>Throughout the length of the intestine</p> Signup and view all the answers

    What is the role of amylase in saliva?

    <p>To initiate starch digestion</p> Signup and view all the answers

    What is the importance of the surface area of the intestine?

    <p>It allows for the absorption of nutrients</p> Signup and view all the answers

    What is the primary action of cholecystokinin (CCK) in the pancreatic function?

    <p>Stimulation of pancreatic enzyme secretion</p> Signup and view all the answers

    What is the effect of cholecystokinin (CCK) on the gallbladder?

    <p>Contraction of the gallbladder</p> Signup and view all the answers

    What is the function of immunoglobulin A in saliva?

    <p>To protect the oral cavity from bacteria</p> Signup and view all the answers

    What is the effect of cholecystokinin (CCK) on gastric emptying?

    <p>Inhibition of gastric emptying</p> Signup and view all the answers

    What is the primary stimulus for the secretion of cholecystokinin (CCK)?

    <p>Contact of the intestinal mucosa with peptides and amino acids</p> Signup and view all the answers

    Where else is cholecystokinin (CCK) found in the body besides the I cells in the small intestine?

    <p>In nerves in the distal ileum and colon, and in neurons in the brain</p> Signup and view all the answers

    What is the possible role of cholecystokinin (CCK) in the brain?

    <p>Regulation of food intake</p> Signup and view all the answers

    What is the unique role of bile in the body's cholesterol disposal process?

    <p>It is the only route by which the body can dispose of cholesterol</p> Signup and view all the answers

    What is the primary function of the bile acids in the digestive process?

    <p>They represent the most important components of bile</p> Signup and view all the answers

    What is the term used to describe the circulation of bile components in the body?

    <p>Enterohepatic circulation</p> Signup and view all the answers

    What is the composition of bile?

    <p>Bile acids, bile pigments, and an alkaline electrolyte solution</p> Signup and view all the answers

    How does the body regulate the functions of the gastrointestinal tract?

    <p>Through the release of hormones triggered by meal-associated stimuli</p> Signup and view all the answers

    What is responsible for the yellow color of bile?

    <p>The glucuronides of bilirubin and biliverdin</p> Signup and view all the answers

    What is unique about the composition of saliva?

    <p>It is hypotonic compared to plasma</p> Signup and view all the answers

    Which branch of the autonomic nervous system controls salivary secretion?

    <p>Parasympathetic branch</p> Signup and view all the answers

    What is the primary function of saliva in relation to food?

    <p>To facilitate swallowing</p> Signup and view all the answers

    What is the primary purpose of the stomach in the digestive process?

    <p>To store and mix food with digestive juices</p> Signup and view all the answers

    What is the significance of the alkaline nature of saliva?

    <p>It helps to neutralize gastric secretions that reflux into the esophagus</p> Signup and view all the answers

    What happens during the cephalic phase of gastric secretion?

    <p>The stomach readies itself to receive the meal before it is actually taken in</p> Signup and view all the answers

    What is the primary action of gastrin on the stomach?

    <p>Stimulation of gastric acid and pepsin secretion</p> Signup and view all the answers

    What is the source of gastrin production in the body?

    <p>G cells in the antral portion of the gastric mucosa</p> Signup and view all the answers

    What inhibits gastrin secretion?

    <p>Acid in the antrum</p> Signup and view all the answers

    What is the term for the local action of mediators on cells in the local area?

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

    What is the function of the enteric nervous system?

    <p>Regulation of digestion and absorption</p> Signup and view all the answers

    What is the connection between the enteric nervous system and the central nervous system?

    <p>Extrinsic innervation</p> Signup and view all the answers

    Study Notes

    Overview of Gastrointestinal Function & Regulation

    • The primary function of the gastrointestinal tract is to serve as a portal for nutrient and water absorption into the body.

    Gastrointestinal Secretions

    • Salivary secretion:
      • Produced by three pairs of salivary glands (parotid, submandibular, and sublingual glands)
      • Organic constituents initiate digestion (amylase) and protect the oral cavity from bacteria (immunoglobulin A and lysozyme)
    • Gastric secretion:
      • Food is stored in the stomach and mixed with acid, mucus, and pepsin
      • The stomach adds a significant volume of digestive juices to the meal
      • The stomach readies itself to receive the meal before it is actually taken in (cephalic phase)
    • Pancreatic secretion:
      • Contains enzymes essential for digestion
      • Bile is the only route for the body to dispose of cholesterol (either in its native form or following conversion to bile acids)
      • About 500 mL of bile is secreted per day
    • Biliary secretion:
      • Bile acids are essential for the digestion and absorption of fats
      • Bile is made up of bile acids, bile pigments, and other substances dissolved in an alkaline electrolyte solution
      • Some components of bile are reabsorbed in the intestine and then excreted again by the liver (enterohepatic circulation)

    Gastrointestinal Regulation

    • There are three main modalities for gastrointestinal regulation:
      1. Endocrine regulation: hormones released by triggers associated with the meal travel through the bloodstream to change the activity of a distant segment of the gastrointestinal tract
      2. Paracrine regulation: mediators alter the function of cells in the local area where they are released
      3. Neural regulation: the intestinal system has extensive neural connections, including connections to the central nervous system and a largely autonomous enteric nervous system
    • Hormones involved in gastrointestinal regulation include:
      • Gastrin: stimulates gastric acid and pepsin secretion, and the growth of the mucosa of the stomach and small and large intestines
      • Secretin: increases the secretion of bicarbonate by the duct cells of the pancreas and biliary tract, and augments the action of CCK in producing pancreatic secretion of digestive enzymes
      • Gastric Inhibitory Peptide (GIP): stimulates insulin secretion and inhibits gastric secretion and motility
      • Motilin: produces contraction of smooth muscle in the stomach and intestines in the period between meals
      • Somatostatin: inhibits the secretion of gastrin, VIP, GIP, secretin, and motilin, and is stimulated by acid in the lumen

    Enteric Nervous System

    • The enteric nervous system is a complex network of nerve fibers intrinsic to the gastrointestinal tract
    • It contains about 100 million sensory neurons, interneurons, and motor neurons
    • It regulates gastrointestinal function through two major networks of nerve fibers: the myenteric plexus (Auerbach plexus) and the submucous plexus (Meissner plexus)### Hormonal Regulation of Digestion
    • Gastrin secretion increases acid secretion, but the resulting acid inhibits further gastrin secretion.

    Cholecystokinin (CCK)

    • CCK is secreted by I cells in the mucosa of the upper small intestine.
    • The main actions of CCK are:
      • Stimulating pancreatic enzyme secretion
      • Contracting the gallbladder
      • Relaxing the sphincter of Oddi, allowing bile and pancreatic juice to flow into the intestinal lumen
      • Inhibiting gastric emptying
      • Exerting a trophic effect on the pancreas
      • Enhancing the motility of the small intestine and colon
    • CCK is also found in:
      • Nerves in the distal ileum and colon
      • Neurons in the brain, particularly the cerebral cortex
      • Nerves in various parts of the body
    • In the brain, CCK is involved in regulating food intake and is related to anxiety and analgesia production.
    • CCK secretion is increased by contact between the intestinal mucosa and products of digestion, such as peptides and amino acids.

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    Description

    Learn about the role of acetylcholine, vagal input, and meal constituents in stimulating gastric secretion during the cephalic phase.

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