Physiology: Gastrointestinal
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Questions and Answers

What is the function of the circular muscle in the gastrointestinal tract?

  • Increases the surface area for secretion or absorption
  • Decreases the diameter of the lumen of the GI tract (correct)
  • Causes shortening of a segment of the GI tract
  • Enhances the motility of the GI tract

    • Which nervous system carries sensory information from chemoreceptors and mechanoreceptors in the GI tract to the brainstem and spinal cord?

  • Afferent nervous system (correct)
  • Enteric nervous system
  • Sympathetic nervous system
  • Parasympathetic nervous system

    • What is the function of the muscularis mucosa in the gastrointestinal tract?

  • Decreases the diameter of the lumen of the GI tract
  • Increases the surface area for secretion or absorption
  • Changes the surface area for secretion or absorption (correct)
  • Causes shortening of a segment of the GI tract

    • Which of the following nerves carries parasympathetic signals to the GI tract?

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

    What is the function of the enteric nervous system in the GI tract?

    <p>Integrates and coordinates motility, secretory, and endocrine functions</p> Signup and view all the answers

    What is the function of the longitudinal muscle in the gastrointestinal tract?

    <p>Causes shortening of a segment of the GI tract</p> Signup and view all the answers

    What is the primary function of the myenteric plexus (Auerbach plexus)?

    <p>Controlling the motility of the GI smooth muscle</p> Signup and view all the answers

    What is the function of the submucosal plexus (Meissner plexus)?

    <p>Controlling secretion and blood flow</p> Signup and view all the answers

    What is necessary for the release of GI hormones into the portal circulation?

    <p>Endocrine cells in the GI mucosa</p> Signup and view all the answers

    What do gastrin, cholecystokinin (CCK), secretin, and glucose-dependent insulinotropic peptide (GIP) have in common?

    <p>They are all considered 'official' GI hormones</p> Signup and view all the answers

    What is the primary route by which GI hormones enter the general circulation?

    <p>Through the portal circulation</p> Signup and view all the answers

    What type of receptors do GI hormones act on?

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

    What is the response of G cells in the gastric antrum to a meal?

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

    What is the effect of atropine on vagally mediated gastrin secretion?

    <p>No effect on gastrin secretion</p> Signup and view all the answers

    What is the function of somatostatin in the stomach?

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

    What is the characteristic of the C-terminal heptapeptide of CCK?

    <p>Contains the sequence homologous to gastrin</p> Signup and view all the answers

    What is the effect of CCK on the gallbladder and sphincter of Oddi?

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

    What is the term for a tumor that secretes gastrin from non-beta cells of the pancreas?

    <p>Zollinger-Ellison syndrome</p> Signup and view all the answers

    What is the effect of CCK on gastric emptying?

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

    What is a stimulus for the release of secretin?

    <p>Fatty acids in the lumen of the duodenum</p> Signup and view all the answers

    What is a function of secretin?

    <p>Stimulates pancreatic HC03- secretion</p> Signup and view all the answers

    What is a characteristic of GIP?

    <p>Contains 42 amino acids and is homologous to secretin and glucagon</p> Signup and view all the answers

    What is the effect of secretin on the liver?

    <p>Stimulates HC03- and H2O secretion</p> Signup and view all the answers

    What is a function of CCK?

    <p>Stimulates growth of the exocrine pancreas</p> Signup and view all the answers

    What is unique about GIP compared to other GI hormones?

    <p>It is the only GI hormone that is released in response to all three macronutrients</p> Signup and view all the answers

    What is the effect of GIP on insulin release?

    <p>It stimulates insulin release</p> Signup and view all the answers

    What is the function of GLP-1?

    <p>It stimulates insulin secretion</p> Signup and view all the answers

    What is the effect of somatostatin on GI hormones?

    <p>It inhibits the release of all GI hormones</p> Signup and view all the answers

    What is the function of molilin?

    <p>It increases GI motility</p> Signup and view all the answers

    What is the characteristic of paracrines?

    <p>They are released by endocrine cells in the GI mucosa and diffuse over short distances to act on target cells in the GI tract</p> Signup and view all the answers

    What is the primary action of VIP on the GI smooth muscle?

    <p>Produces relaxation</p> Signup and view all the answers

    Which peptide is involved in the treatment of diarrhea?

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

    What is the primary action of GRP (bombesin) on G cells?

    <p>Stimulates gastrin release</p> Signup and view all the answers

    What is the effect of leptin on appetite?

    <p>Decreases appetite</p> Signup and view all the answers

    What is the location of the satiety center in the hypothalamus?

    <p>Ventromedial nucleus</p> Signup and view all the answers

    What is the effect of enkephalins on intestinal secretion?

    <p>Inhibits intestinal secretion of fluid and electrolytes</p> Signup and view all the answers

    What is the primary function of ghrelin?

    <p>Stimulating orexigenic neurons</p> Signup and view all the answers

    What type of muscle is found in the pharynx, upper one-third of the esophagus, and external anal sphincter?

    <p>Striated muscle</p> Signup and view all the answers

    What is the result of depolarization of circular muscle in the GI tract?

    <p>Contraction of a ring of smooth muscle and decrease in diameter</p> Signup and view all the answers

    What is the origin of slow waves in the GI tract?

    <p>Interstial cells of Cajal</p> Signup and view all the answers

    What is the effect of action potentials on slow waves in the GI tract?

    <p>They produce subsequent contraction</p> Signup and view all the answers

    What is the characteristic of phasic contractions in the GI tract?

    <p>They occur periodically</p> Signup and view all the answers

    What is the primary mechanism that determines the pattern of action potentials in smooth muscle cells?

    <p>Cyclic opening of Ca2+ channels</p> Signup and view all the answers

    Where is the swallowing reflex coordinated?

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

    What is the function of chewing in the digestive process?

    <p>Mixes food with saliva and begins the digestive process</p> Signup and view all the answers

    What is the frequency range of slow waves in the stomach?

    <p>3 slow waves/min</p> Signup and view all the answers

    What is the role of fibers in the vagus and glossopharyngeal nerves in swallowing?

    <p>Carry sensory information from the GI tract to the medulla</p> Signup and view all the answers

    What determines the maximum frequency of contractions in each part of the GI tract?

    <p>The frequency of slow waves</p> Signup and view all the answers

    What is the role of enterochromaffin cells in the peristaltic reflex?

    <p>They release serotonin to stimulate IPANs.</p> Signup and view all the answers

    What happens to the longitudinal muscle in front of the food bolus during the peristaltic reflex?

    <p>It relaxes, allowing the food to move forward.</p> Signup and view all the answers

    What is the effect of gastrin on the gastrointestinal tract?

    <p>It increases peristalsis in the small intestine.</p> Signup and view all the answers

    What is the function of the ileocecal sphincter?

    <p>It prevents reflux of food from the large intestine into the small intestine.</p> Signup and view all the answers

    What is the effect of food in the stomach on peristalsis in the ileum?

    <p>It increases peristalsis in the ileum.</p> Signup and view all the answers

    What is the function of segmentation contractions in the proximal colon?

    <p>They mix the contents of the colon.</p> Signup and view all the answers

    What is the neurotransmitter involved in the relaxation of the lower esophageal sphincter?

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

    What occurs if the tone of the lower esophageal sphincter is decreased?

    <p>Gastroesophageal reflux</p> Signup and view all the answers

    What is the term for the relaxation of the orad region of the stomach to accommodate the ingested meal?

    <p>Receptive relaxation</p> Signup and view all the answers

    What is the function of the orad region of the stomach?

    <p>Receiving the ingested meal</p> Signup and view all the answers

    What is the antrum responsible for in the stomach?

    <p>Mixing food and propelling it into the duodenum</p> Signup and view all the answers

    What is the function of the fundus and proximal body of the stomach?

    <p>Receiving the ingested meal</p> Signup and view all the answers

    What is the primary function of salivary a-amylase in the gastrointestinal tract?

    <p>Breaking down starches into simple sugars</p> Signup and view all the answers

    What is the characteristic of saliva at the lowest flow rates?

    <p>Lowest osmolarity and lowest Na+, Cl-, and HCO3- concentrations</p> Signup and view all the answers

    What is the effect of parasympathetic nervous system on salivary secretion?

    <p>Stimulates salivary secretion</p> Signup and view all the answers

    What is the characteristic of salivary glands in terms of their size and secretion volume?

    <p>Small glands with high secretion volume</p> Signup and view all the answers

    What is the effect of atropine on salivary secretion?

    <p>Inhibits salivary secretion</p> Signup and view all the answers

    What is the primary ion found in high concentration in saliva?

    <p>K+</p> Signup and view all the answers

    What is the primary reason for saliva becoming hypotonic in the ducts?

    <p>More solute than water is reabsorbed by the ducts</p> Signup and view all the answers

    What is the effect of aldosterone on the ductal cells?

    <p>It increases the reabsorption of Na+ and Cl-</p> Signup and view all the answers

    What is the composition of saliva at high flow rates?

    <p>High Na+ and Cl- concentrations, low K+ concentration</p> Signup and view all the answers

    What is the effect of the ducts on the initial saliva?

    <p>The ducts reabsorb Na+ and Cl-, and secrete K+ and HC03-</p> Signup and view all the answers

    What is the relationship between the flow rate and the composition of saliva?

    <p>The flow rate determines the contact time available for reabsorption and secretion processes</p> Signup and view all the answers

    What is the initial composition of saliva?

    <p>Isotonic with the same Na+, K+, Cl-, and HC03- concentrations as plasma</p> Signup and view all the answers

    What stimulates the release of HCI from parietal cells?

    <p>Vagal stimulation via acetylcholine</p> Signup and view all the answers

    Which of the following is NOT a stimulus for increasing saliva production?

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

    What is the function of chief cells located in the body of the stomach?

    <p>Secretion of pepsinogen</p> Signup and view all the answers

    What is the effect of vagal stimulation on gastric secretion?

    <p>Release of gastrin from G cells</p> Signup and view all the answers

    What is the effect of somatostatin on G cells?

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

    What is the primary composition of the initial saliva produced by the acinus?

    <p>Similar to plasma with a lower concentration of HCO3- and Cl-</p> Signup and view all the answers

    What is the location of G cells that secrete gastrin?

    <p>Antrum of the stomach</p> Signup and view all the answers

    What is the effect of CCK on pancreatic secretion?

    <p>It increases the release of pancreatic enzymes</p> Signup and view all the answers

    What is the role of myoepithelial cells in the salivary glands?

    <p>They contract and eject saliva into the mouth</p> Signup and view all the answers

    What is the effect of secretin on the pancreas?

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

    What is the relationship between the flow rate of saliva and its composition?

    <p>The composition of saliva changes with the flow rate, with a lower concentration of HCO3- and Cl- at higher flow rates</p> Signup and view all the answers

    What is the function of the parasympathetic nervous system in the regulation of pancreatic secretion?

    <p>It potentiates the effect of secretin on pancreatic secretion</p> Signup and view all the answers

    What is the neurotransmitter released by the vagus nerve that stimulates gastrin secretion in the indirect pathway?

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

    Which receptor is responsible for receiving the signal from ACh in the direct pathway?

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

    What is the effect of atropine on the indirect pathway?

    <p>It has no effect on H+ secretion</p> Signup and view all the answers

    What is the second messenger used in the signaling pathway of CCK?

    <p>IP1 and increased intracellular [Ca2+]</p> Signup and view all the answers

    What is the effect of vagotomy on the indirect pathway?

    <p>It eliminates both direct and indirect pathways</p> Signup and view all the answers

    What is the second messenger involved in the stimulation of H+ secretion by histamine in gastric parietal cells?

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

    Which of the following agents potentiates the actions of ACh and gastrin in stimulating H+ secretion in gastric parietal cells?

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

    What is the effect of atropine on vagally mediated gastrin secretion?

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

    What is the primary mechanism by which ACh, histamine, and gastrin produce maximal effects on H+ secretion in gastric parietal cells?

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

    Which of the following agents is particularly effective in treating ulcers because it blocks both the direct action of histamine on parietal cells and the potentiating effects of histamine on ACh and gastrin?

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

    What is the primary mechanism by which histamine stimulates H+ secretion in gastric parietal cells?

    <p>Activation of H2 receptors on the parietal cell membrane</p> Signup and view all the answers

    What is the primary mechanism of absorption for fatty acids, monoglycerides, and cholesterol in the small intestine?

    <p>Micelles form with bile salts in intestinal lumen</p> Signup and view all the answers

    Which of the following vitamins requires intrinsic factor for absorption in the ileum of the small intestine?

    <p>Vitamin B12</p> Signup and view all the answers

    What is the mechanism of absorption for carbohydrates in the small intestine?

    <p>Na-dependent cotransport</p> Signup and view all the answers

    How are amino acids absorbed in the small intestine?

    <p>Na-dependent cotransport</p> Signup and view all the answers

    What is the site of absorption for lipids, including fatty acids and cholesterol?

    <p>Small intestine</p> Signup and view all the answers

    Which of the following is NOT a mechanism of absorption in the small intestine?

    <p>Simple osmosis</p> Signup and view all the answers

    What is the result of CCK on gastric emptying?

    <p>It slows gastric emptying</p> Signup and view all the answers

    What is the role of bile acids in the small intestine?

    <p>They increase the surface area for digestion by emulsifying lipids</p> Signup and view all the answers

    What is the purpose of micelles in the small intestine?

    <p>They solubilize the products of lipid digestion and bring them into contact with the absorptive surface of the intestinal cells</p> Signup and view all the answers

    What is the fate of glycerol in the intestinal cells?

    <p>It is not contained in the micelles due to its hydrophilic nature</p> Signup and view all the answers

    What is the consequence of the lack of apoprotein B in the intestinal cells?

    <p>The inability to transport chylomicrons out of the intestinal cells</p> Signup and view all the answers

    What is the role of pancreatic lipases in the small intestine?

    <p>They hydrolyze lipids to fatty acids, monoglycerides, cholesterol, and lysolecithin</p> Signup and view all the answers

    What is the mechanism by which glucose stimulates the absorption of Na+ in oral rehydration solutions?

    <p>Na+-glucose cotransport</p> Signup and view all the answers

    How is vitamin B12 absorbed in the ileum?

    <p>By binding to a receptor on the ileal cells</p> Signup and view all the answers

    What is required for calcium absorption in the small intestine?

    <p>The presence of adequate amounts of the active form of vitamin D</p> Signup and view all the answers

    What is the fate of heme iron in the intestinal cells?

    <p>It is degraded and free Fe2+ is released</p> Signup and view all the answers

    What is the result of gastrectomy on vitamin B12 absorption?

    <p>Decreased absorption</p> Signup and view all the answers

    What is the function of calbindin D-28K in calcium absorption?

    <p>Induces the synthesis of an intestinal Ca2+-binding protein</p> Signup and view all the answers

    In which part of the gastrointestinal tract is Na+-glucose cotransport, Na+-amino acid cotransport, and Na+-H+ exchange mechanisms most important?

    <p>Small intestine</p> Signup and view all the answers

    What is the primary mechanism of Na+ absorption in the colon?

    <p>Passive diffusion via Na+ channels</p> Signup and view all the answers

    Which of the following mechanisms is involved in Cl- absorption throughout the GI tract?

    <p>All of the above</p> Signup and view all the answers

    What is the mechanism of K+ absorption in the small intestine?

    <p>Passive diffusion via a paracellular route</p> Signup and view all the answers

    What is the primary ion secreted into the intestinal lumen?

    <p>Cl-</p> Signup and view all the answers

    What is the mechanism of K+ secretion in the colon?

    <p>A mechanism similar to that for K+ secretion in the renal distal tubule</p> Signup and view all the answers

    What is the effect of cholera toxin on the intestinal epithelium?

    <p>It catalyzes adenosine diphosphate ribosylation of the a subunit of the G protein</p> Signup and view all the answers

    What is the mechanism of coupling solute and water absorption in the small intestine and gallbladder?

    <p>Similar to that in the renal proximal tubule</p> Signup and view all the answers

    What is the similarity between the Na+ channels in the colon and those in the renal system?

    <p>They are similar to those in the renal distal tubule and collecting ducts</p> Signup and view all the answers

    What is the reason for the low H2O permeability in the colon?

    <p>The specific structure of the colon epithelium</p> Signup and view all the answers

    What is the result of excessive K+ loss in diarrheal fluid?

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

    What is the location of the absorptive mechanisms in the GI tract?

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

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