Gastrointestinal Study Guide
Gastrointestinal Study Guide PGY 451LEC
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This 11 page Study Guide was uploaded by UBnotetaker on Friday November 6, 2015. The Study Guide belongs to PGY 451LEC at University at Buffalo taught by Baizer, J S in Fall 2015. Since its upload, it has received 39 views. For similar materials see Human Physiology I in Physiology at University at Buffalo.
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Date Created: 11/06/15
Gastrointestinal Physiology Anatomy 1. The stomach is divided into three parts; what are they? a. The Fundus, Body, and Antrum 2. Which portion of the Small Intestines is the smallest? Which is the longest? a. Duodenum and Jejunum, respectively 3. Food that is transferring from the mouth to the small intestines what major sphincters are along the way? a. Upper esophageal, Lower esophageal, and the pyloric 4. What differentiates endocrine from exocrine? a. Exocrine cells produce chemicals that stay in circulation; exocrine chemicals move outside of the body 5. Between what structures is the sphincter of Oddi? a. The liver, gall bladder, and pancrease AND the Duodenum of the Small Intestines 6. Where is the dividing line between the Duodenum and Jejunum? The Jejunum and the Ilium? a. Impossible to tell for either of them…the transition is not drastic. 7. How does the anatomy of the upper and lower Esophageal sphincters differ? a. The lower is not a true sphincter, but rather a thickening of the smooth muscle, which makes it slightly leaky 8. How does the bacterial presence of the small intestines compare to the Large? What separates the two? a. It is fairly sterile. It is separated by the Ileocecal valve 9. True or False? Accessory organs are in many cases unnecessary and can be surgically removed. a. False. Organs like the Liver and Pancreas are vital to life and cannot be done without. 10. How does “Receptive Relaxation” apply to the stomach? a. The stomach has the capability to expand itself in response to the addition of food, which keeps pressure at a constantly low level. 11. True or False. The stomach is able to expand because there are invaginations on the surface forming crypts, where there is also secretion of acid. a. False. Expansion of the stomach occurs because of Rugae; the surface epithelium that forms crypts are different, in that the form the surface layer of the Rugae, but do not provide the expansion factor themselves. 12. True or False. In the stomach, blood Vessels permeate the Mucosa, exclusively. a. False. The blood vessels extend into the mucosa but originate in the submucosa. 13. How does the number of neurons of the Enteric Nervous system compare to the CNS? What is special about it? a. There are as many as in the Spinal cord. It is able to regulate and control itself without CNS control, but does work with some CNS influence. 14. What types of muscle are present in the stomach? What are their functions a. Longitudinal (for lengthwise contraction), Circular (for width contraction), and oblique (for torsional motion) 15. What is the purpose for Brunner’s Gland? Where is it? - a. It secretes a HCO r3ch solution into the duodenum, upstream from the sphincter of oddi, to neutralize acid to prevent damage to the small intestines. 16. Which of the following is incorrectly paired: (Neuron, NMJ); (Paracrine, interstitial space); (Endocrine, submucosa) a. (Endocrine, submucosa)—endocrine releases hormones into the circulatory system 17. True or False? Gut reflexes are dealt with purely by the Enteric NS, whereas mechanical and chemical stimuli affect the CNS only. a. False. Mechanical and Chemical stimuli can affect the enteric NS too. 18. What differentiates a Long Reflex from a Short Reflex? a. A Long Reflex involves a stimuli causing a reflex in the CNS which in turn passes signals to the Enteric NS, which causes a response. In a short reflex, the stimuli affect the Enteric NS which directly causes a response. 19. True or False? The Vagus Nerve innervates the entire GI tract. a. False. The Vagus Nerve only controls the ascending portion of the large intestines. 20. What does the Enteric NS control in the GI tract? a. Both the smooth muscle and the blood vessels flow rate Motility 1. Other than the mouth is there any striated muscle anywhere in the GI tract? a. Yes, there is some striated muscle in the beginning portion of the esophagus 2. How is the message to contract passed to smooth muscle cells? a. It initiates by a Enteric Neuron, but because of gap junctions, one cell’s depolarization causes the neighboring cell to do the same 3. How do the potentials activating the muscle cell differ from those in a traditional neuron? a. They are multi-second changes in V tham possibly results in a contraction, so long as the amplitude of the wave surpasses the threshold 4. True or False? The Interstitial Cells of Cajal are specialized muscle cells that drive the contraction of the traditional smooth muscles. a. True. 5. What controls the amplitude and frequency of the gut’s pacemakers? a. Extreinsic/intrinsic nerves and hormone 6. Entry of Calcium into a muscle cell can cause a contraction; What channel do they use to enter and what is the main secondary messenger of this system that makes it work? How does it work? 2+ a. Calcium enters through the L-type Ca to form Calmodulin complex. The Calmodulin activates Myosin Light Chain Kinase. This Kinase phosphorylates myosin to cause a contraction of the sarcomere. 7. How do Peristaltic, Segmental, and Migrating Myoelectric Complex differ? a. Peristaltic contractions are waves of contraction and relaxation moving along axis of gut. Segmental contractions provide no net movement designed to mix chime. Migrating Myoelectric Complex provides the waves during fasting that keep the gut clean. 8. The stomach acts as a reservoir for the chyme that will be introduced into the small intestines. What type of muscle movement is present when the chyme stays in the stomach? When it is moving into the duodenum? a. Segmental and Peristaltic, respectively 9. What is Motilin responsible for? a. Migrating Myoelectric Compex Cephalic, Oral, and Esophageal Phases 1. Does the cephalic phase require mechanical stimuli of food to activate? a. No, by definition, it uses thought of food, olfactory, visual, and auditory stimulation 2. If a Blood Cell was placed into the salivary secretions what would happen? Why? What would happen if the blood cell was placed in the solution before it passed through the salivary duct? a. It would fill with water, because saliva is a hypotonic solution. If the blood cell was placed into the salivary fluid before the duct, nothing would happen to the cell because the solution is isotonic before it passes through the salivary duct. 3. What are the three main salivary glands? Are there others? a. Parotid, Submandibular, and Sublingual. Yes there are hundreds throughout the oral cavity 4. What are the main components of salivary secretions? a. Hypotonic watery solution, mucus, digestive enzymes, and anti-bacterial enzymes 5. The blind end of the salivary duct secretes what? How about the duct? a. Electrolytes, mucus, and proteins from the blind end. Ionic modification in duct (add K and HCO , reduce Na and Cl) 3 6. What is Lysozyme used for? a. Kill bacteria 7. What structure keeps the epithelial cells oriented as to provide a coherent movement of substance across the membrane? a. Tight junctions, because the keep the cells tightly connected and oriented in a single direction 8. How does transport on the lumen side of an Acinar cell differ from a Duct cell? a. Acinar cells push K, Cl, and HCO int3 the lumen. Whereas the duct removes Na, Cl, and protons; it adds K and HCO in3o the lumen. 9. True or False? In the salivary glands, ions can move only through membrane channel proteins. a. False, some ions, such as Na, are able to pass into the lumen of the salivary gland by going between cells. 10. How is Salivary secretions controlled? a. They are controlled neurologically: Both Sympathetic and Parasympathetic(the major force) stimulate 11. Where is the swallowing reflex controlled? a. The Medulla and lower pons 12. What is the stimuli that causes the stomach to relax? a. The vary presence of food going into the stomach causes relaxation and a lowering of pressure Gastric Phase 1. What factors cause the release for acid and Pepsinogen? a. Vagovagal reflex and endocrine in the form of Gastrin 2. Which of the following mechanisms best describes the relationship of signaling in the GI system: Positive Feedback; Negative Feedback; Feed Forward? What is an example of each? a. Feed Forward for the most part (stimuli in the cephalic phase cause activation of the gut), but also some positive (activation of more pepsinogen by pepsin), and negative feedback (Somatostatin released in response to low pH causing deactivation of parietal cells) 3. What is the purpose of having an inactive and active form of gastric enzymes? a. An inactive form prevents the enzyme from digesting the very cell that produces it and allows it to be safely sequestered within the ER/Golgi endomembrane system and readied for release into the gastric lumen. 4. What secretes intrinsic factor? What is its purpose? a. The parietal cell; it is designed to bind with vitamin B12 in order to prevent its breakdown in the gut. 5. What are the canaliculi? How does its structure change? a. They are designed to direct the large amount of acidic protons outside of the cell via ATP pumps. They are fairly spread out in an inactive parietal cell, but once activated, the structure comes together and is directed towards the gastric lumen. 6. What is the purpose of the ECL cell? Where is it? What stimulates it a. The ECL cell releases the paracrine histamine, the largest driving force for acid secretion. They are located in the submucosa of the body of the stomach and are activated by both G cells and Neurons 7. G Cells are primarily located in what part of the stomach? a. The antrum 8. How does the combined effect of Gastrin and Ach compare to their individual efforts on ECL cells? a. Together they promote the release of a large amount of Histamine, apart they stimulate the release of a lesser amount. 9. What is the order for strength of stimulation that can activate Parietal cells? a. Histamine>Ach>Gastrin 10. What is the stimulus of D Cells? What do they release and what does that product do? a. D Cells are stimulated by high proton concentration, which causes a release of somatostatin via a paracrine action. This product causes the deactivation of G cells. 11. What is the activity of neurons if a D cell is active? a. Ach release from neurons decreases as the stomach is at capacity and is no longer accepting food 12. What do Chief Cells produce? a. Pepsinogen 13. True or False? Activation of Chief cells, Parietal cells, ECL cells, and G cells is caused by neurons from the vagus nerve? a. False. The Vagus nerve causes a reaction in the Enteric NS, which intern activates the various secretory cells of the stomach. 14. How does the paricellular movement in the stomach compare to the small intestines? a. The junctions between stomach cells are very tight, permitting little to no transfer of material that way. The cells of the small intestines have fairly leaky gaps between them, allowing the transfer of matter 15. Which pumps in a parietal cell are used for “house-keeping” and which ones are used for gradient generation? a. Hose Keeping: H/Na channels are to keep cytoplasmic pH near 7; Na/K ATP pumps are present and used to keep Sodium gradient in most cells. Gradient production: Chloride channels to lumen; K/H ATP pups to bring K in , H out; HCO /3l pump used to push the bicarbonate byproduct out of the cell 16. What is the purpose of Carbonic Anhyrase? a. It permits the fast hydration of CO to2form bicarbonate and a proton. 17. Blood returning from the stomach during its activation has what type of pH? a. The blood is more alkaline as more bicarbonate has been placed into circulation in recompense for protons being pumped into the lumen of the stomach 18. What is the net movement of Potassium? Chloride? Bicarbonate? Protons? a. Potassium has no net movement. Chloride movement is net out towards lumen. Bicarbonate is net towards blood. And Protons are net towards lumen. 19. Gastrin is picked up by which receptor in the gut? Where are these receptors? a. CCK Regeptor, which is on both the ECL cells and the Parietal Cells 20. D Cells receive excitatory input from where? They receive inhibitory input from where? a. Excitatory: low pH and Gastrin; Inhibitory: Muscarinic Ach 21. If Ach acts upon which receptor? What is the chain of events that ultimately lead to an increase in gastric lumen proton concentration? Which other transmitter molecule uses this pathway? a. Ach binds to the M re3eptorG activaqionPLC activationPLC cleaves PIP 2 2+ into IP3and DAGIP relea3es Ca stores; DAG activates PCA---Ca and PCA cause H-K pump activation. Ach also has the ability for its M rec3ptor do open calcium channels to directly increase intercellular Ca. Gastrin also works via this system excepts starts the chain reaction via the CCK reBeptor. 22. How does Histamine activate the production of gastric acid? a. Histamine binds to H re2eptors which causes the activation of G which sncrease AC activity. The increase of AC causes an increase of cAMP, in turn increasing PKA activity. PKA is the final messenger which activates the K-H pump 23. Should a D-Cell be activated, where would the response be to its secretory product and what are its internal effects? a. Somatostatin is released by D-cells, which acts upon its receptor to activate G i proteins, which causes a decrease in the activity of AC. 24. What is the dehydrated form of mucus called? a. Mucen 25. What issues can arise should tissue injury be incurred in the epithelial layer of the gastric lumen? Why? a. A cyclic effect of Mast cells releasing histamine as part of the immune response causes Parietal cells to release more HCl, thus causing more damage. 26. What is the main type of digestion done by the stomach? What are some other secondary types? a. Mechanical. There is some protein and lipid digestion. 27. What is the purpose of Antral Contractions? a. Provides a mechanism for grinding of the chyme and to mix it with the gastric juices. 28. About how much does the stomach hold at one time? a. A Liter 29. In terms of tonicity, which types of solutions will drain from the stomach faster? a. Isotonic content drains faster than hypo or hypertonic content 30. True or False? Because of the “feed forward” system, there is no talking of the Small intestines to the stomach. a. False, the small intestines provide signals to the stomach based on what is the content of the chyme: protein causes an increase in Gastrin thus activating the stomach further; Fat, acid, hypertonicity, and distention all cause inhibitory signals to be passed on to the stomach Intestinal Phase 1. What are the parts of the Small Intestines, in order? a. Duodenum, Jejunum, Ilium 2. What organ provides the balance to the blood in terms of equating for the excess bicarbonate added by the stomach? How? a. The Pancreas uses the same CA enzyme to produce H and HCO but inve3ts product placement: protons go into blood, bicarbonate enters the duodenum for acid neutralization 3. What do Duct Cells produce? What stimulates them and how? a. Duct cells produce the bicarbonate meant to neutralize the acid. Duct cells are stimulated by secretin from S Cells. 4. What is the purpose of I cells? What activates them a. I cells release CCK in order to activate Acinar cells, which in turn release enzymes from the pancreas. I Cells are activated by small peptides, fatty acids, phenylalanine, Methionine, and tryptophan 5. What is Phenylalanine for? Methionine? Tryptophan? a. They are all signaling molecules that activate I cells 6. Briefly describe the differences in proteases in between the stomach and the small intestine. a. Pepsinogen is activated in the stomach to form pepsin, which provides protein hydrolysis function. In the Small Intestines, Trypsinogen is hydrolycized by enterokinase to form Trypsin. Tripsin then activates a plethora of other proteases. 7. Other than Tripsin, what are the main proteases of the small intestines? a. Chymotrypsin, Elastase, Carboxypeptidease A/B 8. True or False? Hydrolysis breaks down macromolecules by the subtraction of water. a. False, hydrolysis adds water to break polymers 9. Where is the majority of alcohol be absorbed? The minority? a. Small intestines and stomach respectively? 10. Which of the following is/are absorbed by the colon exclusively: Sodium, Potassium, Acids, Gases, Water. a. Acids and Gases 11. What is the overriding regulating factor in the intestinal phase? a. The composition of the chyme: Carbohydrates are digested/absorbed the fastest; proteins are digested/absorbed next; and lipids the slowest. 12. A high fat meal would likely cause the small intestines to release what signal molecule for the stomach? Why? a. CCK—to inhibit gastric emptying 13. What are the two main types of Polysaccharides? How are they different? a. Amylose is a straight chained glucose polymer; Amylopectin is a massively branched glucose polymer 14. Starch is the storage form of glcose in plants. What is its counterpart in animals? a. Glycogen 15. How does Amylase affect Amylose and Amylopectin differently? a. Amylose would produce Maltotriose and Maltose; Amylopectin would produce Maltotriose, Maltos, and α-limit dextrins 16. Where would the carbohydrate digestive enzymes be located? a. In the brush-border (the collective microvilli of a single the enterocytes) on the villi 17. How is the balance between secretion and absorption in the small intestines accomplished? a. Absorption occurs on the villi, secretion of fluid in the crypts 18. How does Sucrase and Isomaltase differ from Lactase and Maltase? a. They work together in a large complex together. 19. What is the channel protein designed to bring Glucose/Galactose into the cell? How does it work? How does this differ from when it leaves the cell? a. SGLT 1 uses a sodium gradient to push both sodium and glucose into the cell. When it leaves the cell there is no need for it to be pushed by a gradient other than its own. 20. True or False? Fructose utilizes a sodium gradient to enter the enterocyte, but does not need one to exit the cell to the blood. a. False, because a normal diet is so high in fructose, it freely enters the cell through a membrane channel, without the aid of the sodium gradient 21. What is the main purpose of acidification in the stomach in terms of protein digestion? a. The low pH denatures the protein in a single polypeptide chain, thus allowing the various proteases to have ready access for breakdown. 22. True or False? Pancreatic enzymes do not provide the breakdown of proteins into their monomeric form (amino acids); they simply break them down into a form that can be handled by the Brush Border enzymes. a. True 23. True or False? Once the Brush Boarder is done hydrolyzing polypeptides to the point of cellular absorption, there is no further modification before they enter circulation. a. False, there are some cytosolic proteases that break 2/3 amino acid peptides into single amino acids 24. How do the luminal membrane transporter proteins differ between tripeptide/dipeptide pumps and single amino acid pumps? a. The tripeptides and dipeptides are moved through a pathway that requires a proton gradient, but single amino acids utilize a sodium gradient. 25. What level of specificity do proteases exhibit? a. Each protease attacks a certain amino acid pair to facilitate the breakdown of any protein 26. How many gradients are generated in order to generate the driving force for dipeptide/tripeptide uptake. a. Two: an ATP Na/K pump creates high internal K and low internal Na. Another Na/K pump uses a sodium gradient to push protons outside towards the lumen. 27. True or False? Other than in infants, whole proteins are never absorbed? a. False, there is a very small amount of whole protein absorption in adults 28. What is the main site of lymph tissue in the gut that acts as a source of immunity? a. Peyer’s Patches 29. How much of lipid digestion occurs in the small intestines? a. ~90% 30. Lipases and Colipases break what substrate into what product? a. Triglycerides into a monoglyceride and two free fatty acids 31. What makes Bile amphipathic? a. Methyl groups provide nonpolar portions, hydroxyl groups create the polar portions 32. How does the mucus layer of the small intestine facilitate lipid intake? How? a. Protons are being pumped out of the enterocytes into the mucus layer of the small intestines (largely more alkaline). The acidic environment causes micelles to break down (because their solubility increase) and diffuse through the membrane. 33. What alterations are made to monoglycerides and free fatty acids in the sER? a. They are reconstituted into triglycerides 34. What is a chylomicron? a. It is a package of triglyceride, cholesterol, and protein that is shipped through the Golgi and out of the cell into the lymphatic system 35. What causes Bile salt release? Where are they taken up for recycle? a. CCK causes the sphincter of Oddi to relax and allow the bile salts to be released. They are reabsorbed by the Ileum and transported through the portal vein for liver filtering. 36. What are the main primary bile acids? The secondary? a. Cholic and Chenodeoxycholic—primary. Deoxycholic and lithocholic acid— secondary 37. What creates primary bile acids? How? Secondary? a. The liver turns cholesterol into primary bile acids. Intestinal bacterial turn primary bile acids into secondary 38. What differentiates Bile acids from Bile salts a. Conjugation. Bile salts are Bile acids conjugated with Taurine or Glycine Top Hat Questions 1. The Passage of a Meal through the GI Tract is controlled by 6 sphincters. Which is third from the mouth? a. Lower esophageal b. Pyloric c. Ileocecal d. Internal Anal e. External Anal 2. The Vagal Nerve Carries Efferent Fibers that make direct synaptic connections on which of the following: a. Mucosa b. Muscularis Mucosae c. Peyer’s Patch d. Meyenteric Plexus e. Enteric Circular Smooth muscle 3. The Interstital Cells of Cajal function are found in the GI tract. Which of the following best describes their function: a. Pace maker cells b. Drive the basic electrical rhythm c. Drive the migrating electrical complex d. A and B e. A and C 4. Saliva is made Alkaline by the salivary duct cells by secreting which of the following: a. Sodium b. Potassium c. Bicarbonate d. Protons e. None of the above 5. The primary signals for stimulation of salivary secretions come from which of the following hormones? a. CCK b. Motilin c. Secretin d. Insulin e. None of the Above 6. The following statements are true regarding the mechanism of hydrogen secretion by the parietal cells of the stomach, except: a. It depends upon sodium-hydrogen exchange at the lumen-facing membrane b. It depends upon the enzyme, carbonic anhydrase (CA) c. It is stimulated by histamine, Ach, and Gastrin d. It is stimulated by the ECL cell e. It requires ATP 7. Match the sequence of secretory products below to their respective cell type: chief cell, Parietal cell, ECL cell, G cell a. Gastrin, HCl, Histamine, Pepsinogen b. Pepsinogen, HCl, Histamine, Gastrin c. HCl, Histamine, Pepsinogen, Gastrin d. Histamine, HCl, Gastrin, Pepsinogen 8. The major stimulus for gastric acid seretion during the cephalic phase is: a. Gastrin b. Histamine c. Ach d. Cephalic-Acid releasing factor e. Secretin 9. Which function(s) is/are NOT continuously regulated by Neural/Hormonal factors in the GI system? a. Absorption b. Secretion c. Motility d. All of the above are regulated 10. The I cells of the Duodenum secrete: a. CCK b. Secretin c. Intestinal Gastrin 11. The S Cells of the Duodenum secrete: a. CCK b. Secretin c. Intestinal Gastrin 12. In the exocrine pancreas, secretin activates which type of cell? a. I cells b. S Cells c. Ductal cells d. Acinar Cells e. G Cells 13. In the Exocrine Pancreas, CCK activates which type of cell? a. I Cells b. S Cells c. Ductal Cells d. Acinar Cells e. G Cells 14. Digestion refers to the: a. Progressive dehydration of indigestible residue b. Input of food into the digestive tract c. Enzymatic breakdown of food d. Absorption of nutrients in the gut e. Effects of chewing, churning, and segmentation 15. Peyer’s Patches are characteristic of the: a. Stomach b. Esophagus c. Pancreas d. Small intestines e. Colon 16. When eaten, nearly 90% of our dietary calories from fat are in the form of: a. Steroids b. Phospholipids c. Triglycerides d. Cholesterol e. Fat-soluble vitamins 17. An Enzyme that will digest proteins into peptides is: a. Lipase b. Amylase c. Maltase d. Enterokinase e. Trypsin 18. A drug that blocks the action of Carbonic Anhydrase in the parietal cell would: a. Decrease the pH of the gastric content b. Increase the pH of the gastric content c. Decrease the activation of pepsinogen d. Increase the activation of pepsin
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