PHPH 701 Exam 1 (GI Physiology; Grillo)

What are the 3 absorbed products of protein digestion?

1. AAs 2. Dipeptides 3. Tripeptides

What are the 4 symptoms of IBS?

1. Abdominal pain 2. Bloating 3. Constipation 4. Diarrhea

What 2 things stimulate release of somatostatin?

1. Acid (low stomach pH) 2. Negative feedback mechanism

What are the 2 enzymes used to digest carbohydrates in the small intestine?

1. Amylase (luminal) 2. Disaccharidases (membrane)

If drugs are the recommended treatment for GERD, then what are the 5 drugs that could be suggested?

1. Antacids (reduce irritation and damage) 2. H2 histamine receptor blockers 3. Proton pump blockers 4. Bicarbonates 5. Pro-motility drugs (increase emptying rate to reduce pressure after a meal), such as metoclopramide and erythromycin

19. Which of the following is true regarding activity of gastric parietal cells and pancreatic duct cells? 1. Both rely upon the activity of carbonic anhydrase to generate protons and bicarbonate. 2. Secretion of H+ from both types of cells will be blocked by omeprazole. 3. Both contain CFTR channels to transport Cl into the lumen. 4. Both are inhibited by acetylcholine acting through muscarinic receptors 5. None of these are correct.

1. Both rely upon the activity of carbonic anhydrase to generate protons and bicarbonate.

What are the 4 general stimuli that initiate vomiting?

1. CTZ in CNS: activated by vestibular stimulation (motion sickness) 2. Chemoreceptors/mechanoreceptors in GI tract: activated by extreme pressure/irritation in stomach/intestine (Ipecac) 3. Visceral afferents outside the CNS: bile ducts, heart, and other organs 4. Input from the CNS: psychic stimuli (odors/fear)

20. Which of the following is true regarding digestion and absorption? 1. Carbohydrates can be transported from the GI lumen only as monosaccharides 2. Protein digestion is initiated in the mouth through the action of salivary enterokinase 3. Products of lipid digestion are absorbed from the GI lumen by secondary active transport with sodium 4. Most protein digestion is completed in the colon through the activity of bacterial enzymes. 5. Proteins can be transported from the GI lumen only as individual amino acids

1. Carbohydrates can be transported from the GI lumen only as monosaccharides

What are the 2 characteristics of secondary active transport involved in absorption in the small intestine?

1. Carrier doesn't use energy directly, but relies on gradients produced by other energy-requiring processes 2. One of the transported molecules can move against a concentration gradient and the other moves down a gradient

What are the 4 sympathetic ganglia of the GI system?

1. Celiac 2. Superior mesenteric 3. Inferior mesenteric 4. Hypogastric

What are the 3 phases of pancreatic secretion?

1. Cephalic phase 2. Gastric phase 3. Intestinal phase

What are the 3 phases of acid secretion?

1. Cephalic phase (anticipatory) 2. Gastric phase (food enters stomach) 3. Intestinal phase (food enters the small intestine)

What 2 things block H2 receptors?

1. Cimetidine 2. Ranitidine

From the side closest to the lumen, what are the 2 parts of the muscularis propria?

1. Circular muscle: contraction narrows lumen; thick and densely innervated 2. Longitudinal muscle: contraction shortens gut; thin and less innervated

What 5 things occur with the rectosphincteric reflex during defecation?

1. Coordination of several muscle groups controlled both voluntarily and involuntarily 2. EAS relaxes voluntarily 3. Forced expiration against a closed glottis (Valsalva maneuver) 4. Voluntary contraction of abdominal muscles 5. Combines with the enteric and spinal reflexes to produce effective defecation

What are the 2 parasympathetic nerves of the GI system?

1. Cranial: primarily Vagus nerve 2. Sacral: pelvic nerve

What are the 2 forms of cellular processing that occur during protein absorption?

1. Dipeptides and tripeptides are further digested to AAs inside villi cells 2. Basolateral transport (facilitated diffusion and secondary active transport)

If lifestyle changes are the recommended treatment for GERD, then what are the 3 changes that could be suggested?

1. Elevation of the head in bed and not lying down after eating - relieve the pressure gradient across the LES 2. Lose weight 3. Avoid foods which decreases LES tone (chocolate, nicotine, alcohol) and foods that irritate the esophagus (acidic juices, hot peppers)

What are the 3 GI system modulators?

1. Endocrine hormones released from endocrine cells of the GI tract into the blood 2. Paracrines released from endocrine cells and act locally on GI tissue 3. Neurotransmitters released by neurons in response to an action potential

From the side closest to the lumen, what are the 3 parts of the mucosal layer?

1. Epithelium: specialized in secretion/absorption; properties depend on the location 2. Lamina propria: connective tissue; blood and lymph vessels 3. Muscularis mucosa: longitudinal smooth muscle; alters surface area

What are the 3 vagal controls of the LES?

1. Excitatory input (rostral DMN) Activates cholinergic enteric neurons Increases contractile tone of LES 2. Inhibitory input (caudal DMN) Activates VIP-containing enteric neurons Relaxes LES during swallowing reflex 3. Vagotomy Enteric neurons control contraction and relaxation (local reflexes) No anticipatory relaxation but essentially normal LES function

During the cephalic phase, the Vagus nerve releases what 2 neurotransmitters?

1. GRP (acts on G-cells to increase gastrin release) 2. Acetylcholine (Increases acid release acting on parietal cells, increases histamine production by ECL cells, inhibits somatostatin production

What 2 things stimulate release of gastrin?

1. GRP (neurotransmitter/Vagal simulation) 2. Peptides/AAs

What 2 things stimulate histamine release?

1. Gastrin 2. Vagus nerve input

9. Which of the following stimulates the release of gastrin during the cephalic phase of stimulated acid secretion? 1. Gastrin-releasing peptide (GRP, bombesin) 2. Products of protein digestion (peptides/amino acids) 3. An increase in the pH of stomach contents 4. Somatostatin 5. All of these act during the cephalic phase

1. Gastrin-releasing peptide (GRP, bombesin)

Vomiting is characterized by what 5 things?

1. General autonomic discharge 2. Salivation 3. Sweating 4. Rapid breathing 5. Irregular heartbeat

What are the 4 gastric secretions?

1. HCl 2. Pepsinogen 3. Intrinsic factor 4. Mucus

What are the 2 leading causes of gastric ulceration?

1. Helicobacter pylori 2. NSAIDs

What are the 5 steps in the mechanism of bile?

1. Hepatocytes continuously synthesize and secrete bile 2. Bile flows out the liver through the bile ducts and fills the gallbladder, where it is stored 3. When chyme reaches the small intestine, CCK is secreted 4. In the small intestine, the bile salts emulsify and solubilize dietary lipids facilitating lipid digestion and absorption 5. Absorption of bile salts from the ileum into the portal circulation, delivery back to the liver, and extraction of bile salts from the portal blood by the hepatocytes

What are the 3 types of diarrhea?

1. Impaired absorption/digestion 2. Osmotic diarrhea 3. Secretory diarrhea

What are the 2 functions of chewing?

1. Improve ability to swallow (reduce particle size, mix food with saliva) 2. Begin digestion of carbohydrates and fat (salivary amylase and lingual lipase)

How do modulators affect the intrinsic activity of GI smooth muscle?

1. Increase effectiveness of depolarization 2. Don't alter slow wave frequency 3. Can alter contraction frequency

What 4 things initiate the rectosphincteric reflex?

1. Increased pressure in the rectum 2. Rectum contracts 3. IAS relaxes 4. Increased contractile tone of the EAS (voluntarily controlled)

Binding of acetylcholine to parietal cells and ECL cells causes what 2 things to occur?

1. Increases acid 2. Increases histamine

What are the 3 treatments of GERD?

1. Lifestyle changes 2. Drugs 3. Surgery

What are the 3 treatments for IBS?

1. Lifestyle changes, monitoring the conditions that lead to onset 2. Drugs for constipation/diarrhea, anxiolytics/antidepressants 3. Several new drugs target serotonin receptor activity

What are the 4 characteristics of multiunit smooth muscle that we discussed?

1. Little or no coupling with other cells 2. Individually controlled 3. Located in GI sphincters 4. Typically exhibit tonic contraction

Jaundice is often indicative of what 2 disorders?

1. Liver failure 2. Gallbladder dysfunction

What are the 2 functions of gastric mucus?

1. Lubrication 2. Protection (epithelial cells secrete bicarbonate)

In what 2 ways are glucose and galactose absorbed by the small intestine?

1. Lumen (absorbed by the same transporter [SGLT1]) 2. Basolateral (facilitated diffusion)

What 3 factors regulated motility in the small intestine?

1. MMC 2. Neural control 3. Reflexes

What are the functions of gastric motility?

1. Mix contents with gastric juice 2. Propel material into the duodenum

What are the 3 characteristics of unitary smooth muscle that we discussed?

1. Most GI smooth muscle 2. Cells are electrically coupled through gap junctions 3. Permits a coordinated contraction of all interconnected cells

What are the 4 major activities of the GI tract?

1. Motility 2. Secretion 3. Digestion 4. Absorption

What are the 3 steps of vomiting?

1. Nausea: decreased gastric motility, increased intestinal motility 2. Retching: retroperistalsis; inspiration against a closed glottis 3. Vomiting: emesis - controlled by vomiting center in medulla

What are the 2 important neurotransmitters/drugs in neural control of small intestine motility?

1. Opiates (morphine) 2. Serotonin (treatment of IBS)

What are the 2 disorders related to protein digestion/absorption?

1. Pancreatic insufficiency: pancreatitis and cystic fibrosis 2. Genetic absence of trypsin

What are the 3 enzymes involved in lipid digestion?

1. Pancreatic lipase 2. Cholesterol ester hydrolase 3. Phospholipase A2

What are the 3 salivary glands?

1. Parotid: entirely serous secretions, no mucus 2. Submaxillary: mixed secretions 3. Sublingual: mixed secretions

What are the 3 proteases that require activation?

1. Pepsinogen: activated by HCl 2. Trypsinogen: activated to trypsin by enterokinase 3. All other pancreatic enzymes: activated by trypsin

What are the 3 reflexes that affect small intestine motility?

1. Peristaltic reflex/law of the intestines 2. Intestino-intestinal reflex 3. Gastro-ileal reflex

What are the 3 locations of skeletal muscle in the GI tract?

1. Pharynx 2. Upper third of esophagus 3. EAS

What are the 3 functional roles of colonic bacteria?

1. Production of vitamin K (necessary for the blood clotting cascade) 2. Metabolism of steroids and sterols (modify the bile salts and deconjugated sex steroids, allowing their reabsorption) 3. Control of overgrowth of bad bacteria

What 3 things occur with the rectosphincteric reflex during relaxation (if defecation doesn't occur)?

1. Rectum relaxes 2. Anus contracts 3. Material moves from the anus back into the rectum

11. The anti-cholinergic drug atropine has multiple effects on GI function. Which of the following is NOT a potential consequence of ingestion of atropine? 1. Sialorrhea 2. Dysphagia 3. Reduced stomach acid production 4. Reduced pancreatic enzyme secretion 5. Constipation

1. Sialorrhea

What 2 things inhibit gastrin release?

1. Somatostatin 2. Paracrine hormone (inhibits ECL and parietal cells)

What are the 3 characteristics of facilitated diffusion involved in absorption in the small intestine?

1. Specific carriers 2. No energy is used 3. Cannot be transported against a concentration gradient

What are the 2 coordinated actions of CCK?

1. Stimulates contraction of the gallbladder 2. Relaxes the sphincter of Oddi and bile flows into the lumen of the duodenum

What are the 3 functions of the gallbladder?

1. Stores bile that is continuously produced by the liver 2. Concentration of bile 3. Ejection of bile

If surgery is the recommended treatment for GERD, then what are the 2 surgeries that could be suggested?

1. Strengthening the LES 2. Selective lesions of the Vagus nerve

What are the 5 steps in lipid absorption in the small intestine?

1. The products of lipid digestion (cholesterol, monoglycerides, lysolecithin, and free fatty acids) are solubilized in the intestinal lumen in mixed micelles 2. The micelles diffuse to the apical (brush-border) membrane 3. Inside the intestinal epithelial cells, the products of lipid digestion are reesterified with free fatty acids on the sER to form the original ingested lipids 4. The reesterified lipids are packaged with apoproteins in lipid-carrying particles called chylomicrons 5. The chylomicrons migrate to the basolateral membranes and exit the cells by exocytosis

What are the 2 stimulants of the cephalic phase?

1. Thoughts of food/conditioned reflexes 2. Tasting and smelling food

What are the 3 characteristics of diffusion involved in absorption in the small intestine?

1. Through membrane pores/through the lipid domain 2. No energy is required 3. Movement dictated by concentration and electrical gradients

What are the 3 characteristics of paracellular transport involved in absorption in the small intestine?

1. Through the tight junctions that surround cells directly into the intracellular space 2. Water and some small electrolytes diffuse down electrochemical gradients 3. Tightness of the tight junctions determine whether the cells can maintain an osmotic gradient

What are the 2 characteristics of primary active transport involved in absorption in the small intestine?

1. Transporter utilizes ATP 2. Can move against a concentration gradient

Secretion of gastric mucus is stimulated by what 4 things?

1. Vagal stimulation 2. Eating a meal 3. Chemical/physical irritation 4. Prostaglandins - especially inflammatory response

What are the 3 components of the gastric phase?

1. pH (food acts as a buffer, increasing pH above 3): Decreases somatostatin release 2. Distention (pressure activates mechanoreceptors): Vagovagal and intrinsic neural reflexes (acetylcholine) (Stimulate gastrin release, decrease somatostatin release, increase acid secretion 3. Peptides/AAs : Stimulate gastric release

The intestinal phase accounts for _________ of the stimulated response

10%

Questions 14-18: Match each of the following with its neural mediator. Answers may be used more than once or not at all. _____14) Intestinointestinal reflex _____15) Peristaltic reflex _____16) Receptive relaxation _____17) Migrating motility complex _____18) Mass movements in the large intestine 1. Enteric nervous system 2. Parasympathetic nervous system 3. Sympathetic nervous system

14) 3. Sympathetic nervous system 15) 1. Enteric nervous system 16) 2. Parasympathetic nervous system 17) 1. Enteric nervous system 18) 1. Enteric nervous system

13. Which of the following is absorbed from the intestinal lumen by transporters located only in the terminal ileum? 1. Cholesterol 2. Bile salts 3. Glucose 4. Vitamin A (Vitamin A is a fat-soluble vitamin) 5. Both 2 and 4

2. Bile salts

1) Which of the following statements regarding gastric acid secretion is TRUE? 1. Cimetidine reduces acid secretion by blocking the H+ /K+ ATPase 2. Both gastrin and acetylcholine bind to receptors on parietal cells and stimulate acid production 3. Acetylcholine directly increases both gastrin and somatostatin production 4. Most gastric ulcers result from overproduction of stomach acid 5. Somatostatin is a paracrine hormone that increases gastric acid secretion

2. Both gastrin and acetylcholine bind to receptors on parietal cells and stimulate acid production

12. Which of the following is NOT transported from the intestinal lumen by secondary active transport? 1. Galactose 2. Fructose 3. Tryptophan (tryptophan is an amino acid) 4. Bile salts 5. Vitamin C

2. Fructose

Questions 3 - 7 Match the following with their principal secretory cell or site of secretion. Answers may be used more than once or not at all. _____3) Histamine _____4) Pepsinogen _____5) Lactoferrin _____6) Intrinsic Factor _____7) Enterooxyntin 1. Parietal cells 2. Small intestine 3. Salivary glands 4. ECL cells ('enterochromaffin-like') 5. Chief cells

3) 4. ECL cells ('enterochromaffin-like') 4) 5. Chief cells 5) 3. Salivary glands 6) 1. Parietal cells 7) 2. Small intestine

The cephalic phase accounts for _______ of the stimulated response

30%

2) Scleroderma is a disease that causes dysphagia primarily because: 1. It causes uncoordinated, spasmodic contractions of the esophagus. 2. Inflammation of skeletal muscle causes difficulty initiating swallowing. 3. The lower esophageal sphincter (LES) does not relax normally. 4. Damage to connective tissue prevents propagation of a peristaltic wave. 5. Damage to the medulla prevents CNS control of the swallowing reflex

4. Damage to connective tissue prevents propagation of a peristaltic wave.

10. The endocrine hormone motilin could increase the frequency of smooth muscle contractions in the GI tract by: 1. Increasing the frequency of depolarizations of Interstitial cells of Cajal 2. Increasing the frequency of depolarizations in striated muscle cells 3. Increasing the frequency of the basic electrical rhythm 4. Stimulating the parasympathetic nervous system 5. Increasing the amplitude of depolarizations in smooth muscle cells

5. Increasing the amplitude of depolarizations in smooth muscle cells

8. Which of the following will NOT normally result in steatorrhea? 1. Zollinger-Ellison Syndrome 2. Pancreatitis 3. Blockage of the common bile duct by gallstones 4. Inflammation of the terminal ileum 5. Lack of production of intrinsic factor

5. Lack of production of intrinsic factor

By percentage, what is the composition of bile?

51% bile acids 25% phosphatidylcholine 18% pigments, glutathione, xenobiotics, drugs, other lipids, etc. 4% cholesterol 2% bilirubin

What is the anatomic control of chewing?

5th cranial nerve (trigeminal)

The gastric phase accounts for ________ of the stimulated response

60%

Absorption of ________ into the bloodstream during the intestinal phase increases acid release from the parietal cells

AAs

How does the gallbladder eject bile?

AAs and fatty acids increase the release of CCK and acetylcholine. Acetylcholine contracts the gallbladder and relaxes the sphincter of Oddi

________ comes from enteric neurons stimulated by the Vagus nerve. They bind to ________ receptors at the parietal cell, which can be blocked by _________.

Acetylcholine M3 muscarinic acetylcholine Atropine

How is the LES contracted?

Acetylcholine (M3 muscarinic)

What inhibits somatostatin release?

Acetylcholine (Vagus nerve)

_________ results from the failure of the LES to relax

Achalasia

What regulates the aqueous component of the pancreatic secretions?

Acid in the duodenum

What secretes the enzymatic component of the pancreatic secretions?

Acinar cells

How does hormonal regulation help regulate the composition of the salivary gland secretions?

Aldosterone increases Na+ reabsorption and K+ secretion

Severe vomiting causes ________ (loss of H+) and ________ (loss of K+)

Alkalosis Hypokalemia

Secretion of mucus is inhibited by what?

Alpha-adrenergic agonists - may contribute to the effects of stress on development of ulcers

_________ hydrolyzes interior bonds to produce oligosaccharides and disaccharides. It is initiated by _________. Most digestion of this kind is done by _________.

Amylase Salivary amylase Pancreatic amylase

What are the 3 layers of muscle in the stomach?

An outer longitudinal layer, a middle circular layer, and an inner oblique layer that is unique to the stomach The thickness of the muscle wall increases from the proximal stomach to the distal stomach

___________ is associated with chronic acid reflex and includes symptoms such as heartburn, bleeding (blood in vomit/stool), and dysphagia

Barrett's esophagus

What is the role of the bicarbonate/Cl- exchanger in HCl synthesis?

Bicarbonate is transported into the blood in exchange for Cl- Increases the pH of the blood leaving the stomach = alkaline tide

_________ are synthesized from cholesterol by the hepatocytes, transported into the bile duct, stored and concentrated in the gallbladder, and secreted into the intestinal lumen to aid in the digestion and absorption of dietary lipids They are then recirculated from the ileum back to the liver via the ___________ It is necessary for digestion and absorption of _________

Bile acids Enterohepatic circulation Fats

_________ is a metabolite of heme breakdown, which is bound to albumin in the plasma. It is conjugated with _________ in the liver to increase water solubility. It is excreted with ________ into the intestines and eliminated with stool.

Bilirubin Glucuronate Bile

How can sequestrants cause steatorrhea?

Bind to bile to prevent reabsorption Treat high cholesterol and bile-induced diarrhea

What are the parasympathetic long reflexes?

Both the afferent and efferent signals are carried by the same nerve Vago-vagal reflexes specifically for Vagus nerve

_________ is the most common nosocomial pathogen of the GI tract

C. difficile

________ is associated with broad spectrum antibiotics due to loss of normal flora and replacement with a bacterium whose toxic products cause mucosal damage and inflammation

C. difficile colitis

What is carbonic anhydrase's role in HCl synthesis?

Catalyzes formation of HCO3- and H+ from CO2 and water

What is the cause, the symptoms, and the treatment of gastroparesis?

Cause Chronic diabetes (neuropathy) Symptoms Early satiety, nausea, vomiting, anorexia Treatments Change eating habits, pro-motility drugs (life metoclopramide and erythromycin)

What is the cause, the symptoms, and the treatment of dumping syndrome?

Cause Gastrectomy Symptoms (result from acidic/hypertonic solution overwhelming the duodenum and jejunum) Nausea, vomiting, weakness, dizziness after eating Treatment Lifestyle changes (small, more frequency, low-carb meals)

What are the causes and consequences of increased direct bilirubin?

Causes 1. Biliary obstruction (gallstones, pancreatic cancer, etc.) 2. Hepatic necrosis (conjugated B leaks out of ruptured canaliculi) Consequences Jaundice

What are the causes and consequences of increased indirect bilirubin?

Causes 1. Increase in hemolysis (sickle cell, thalassemias, G-6-P dehydrogenase deficiency) 2. Gilbert's syndrome 3. Crigler-Najjar syndrome 4. Acute/chronic liver disease (hepatitis, cirrhosis, etc.) Consequences Jaundice Kericterus in neonates (undeveloped BBB)

What are the causes, consequences, and treatments of GERD?

Causes LES weakness (damage to smooth muscle) Increase in abdominal pressure Obesity, pregnancy Consequences Chronic pain Esophagitis/esophageal ulcers Barrett's esophagus Treatments Most focus on stomach acid

The _________ is initiated by smell, taste, and conditioning and is mediated by the Vagus nerve. This phase produces mainly an __________ secretion

Cephalic phase Enzymatic

__________ is a parasitic infection that destroys the enteric nerves

Chagas' disease

Pepsinogen is secreted by __________. It is converted to its active form by _________. What is its function?

Chief cells/oxyntic glands HCl Protease

________ produces cholesterol and free fatty acid during its reaction

Cholesterol ester hydrolase

How are glucose and galactose absorbed by the lumen of the small intestine?

Co-transported with Na+ (secondary active transport) In the proximal tubules of the kidneys, SGLT1 (10%) and SGLT2 (90%) are responsible for reabsorption of filtered glucose For type II diabetics, drug inhibitors of SGLT2 reduce blood glucose levels by promoting glucose excretion in the urine

How are digested protein products luminally transported in the small intestine?

Co-transporters (secondary active transport)

Fill in the blanks for xerostomia (dry mouth): Common side effect of medications (_________) Typically caused by ________ Treatment: __________

Cold medicine/anticholinergics/antidepressants Radiation therapy/nerve damage Muscarinic agonists (pilocarpine)

What is the function of the enzymatic component of the pancreatic secretions?

Complete digestion of fat, protein, and carbohydrates

How do serotonin antagonists affect small intestine mobility?

Decrease contraction and secretion (treat diarrhea)

What is the overall effect of sympathetic innervation of the GI tract?

Decreased GI activity

In infants or others lacking voluntary control of the EAS, the rectosphincteric reflex will initiate __________

Defecation

How is Barrett's esophagus diagnosed and treated?

Diagnosis Tissue biopsy Treatments Reduce further damage by treating GERD Monitor for development of cancerous tissue (Barrett's is risk factor for esophageal cancer [5-10% develop cancer])

How are lipids digested in the small intestine?

Digestion of lipids depends on emulsifying the fat by mixing it with amphipathic molecules such as bile salts

________ digest oligosaccharides. They are located on the _________ of GI epithelial cells. They produce 3 absorbable products: _________.

Disaccharidases Brush border Glucose, galactose, and fructose

How can inadequate bile salts cause steatorrhea?

Diseases affecting liver, gallbladder, or bile ducts Surgical removal/disease of terminal ileum

________ is connective tissue that bulges out in pouches in the large intestine

Diverticula

__________ is infection/inflammation of the diverticula

Diverticulitis

What secretes the aqueous components of the pancreatic secretions?

Duct cells

How does osmolarity help regulate the composition of the salivary gland secretions?

Ducts relatively impermeable to water (tight junctions) Net movement of ions is out of the saliva

_________ is a disorder of gastric motility characterized by rapid emptying

Dumping syndrome

The rectosphincteric reflex is mediated by the _________

ENS

________ is an endocrine hormone released from the duodenum due to the activation of mechanoreceptors by distension of the small intestine during the intestinal phase

Enterooxyntin

The antibiotic _________ activates the motilin receptors

Erythromycin

The ENS can direct all functions of the GI tract, even in the absence of __________ The ENS is located in __________ and controls the contractile, secretory, and endocrine functions of the GI tract These ganglia receive input from the _________ systems, which modulate their activity These ganglia also receive sensory information directly from __________ in the mucosa and send motor information directly to smooth muscle, secretory, and endocrine cells Information is also relayed between ganglia by __________

Extrinsic innervation Ganglia in the myenteric and submucosal plexuses Parasympathetic and sympathetic nervous Mechanoreceptors and chemoreceptors Interneurons

How is fructose absorbed by the small intestine?

Facilitated diffusion (GLUT5)

What regulates the enzymatic component of the pancreatic secretions?

Fat and protein in the duodenum

_________ results from stomach acid entering the esophagus due to LES weakness/failure

GERD

__________ is heartburn, irritation of esophageal lining by stomach acid

GERD

How does the gallbladder concentrate bile?

Gallbladder epithelium actively reabsorbs ions and water (isotonic) Cholesterol and bile salts become more concentrated over time

The _________ is initiated by distention of the stomach and is also mediated by the Vagus nerve. This phase produces mainly an _________ secretion

Gastric phase Enzymatic

_________ is an endocrine hormone produced by G-cells in the pyloric glands. It acts on parietal cells and ECL cells in order to do what 2 things?

Gastrin 1. Increases acid 2. Increases histamine

The _________ results from stomach distention, which stimulates ileal contractions. It is controlled by the __________.

Gastro-ileal reflex Parasympathetic nervous system

The ________ results from distention of the stomach, and increases colonic motility and frequency of mass movements. It is controlled by the _________

Gastrocolic reflex Parasympathetic nervous system

_________ is a disorder of gastric motility characterized by delayed emptying

Gastroparesis

_________ is blocked by drugs such as omeprazole (Prilosec), used to reduce acid production and treat GERD and ulcers

H+/K+ ATPase

_________ is the most common cause of gastric ulcers. Ulcers result when stress, diet, or lifestyle factors combine with a _________. What is the treatment?

Helicobacter pylori Preexisting infection Antibiotics in combination with antacids

_________ is a congenital disorder caused by a failure of the ENS to develop in a region of the colon, causing constriction

Hirschsprung's disease (megacolon)

________ is a paracrine hormone produced by ECL cells that is the strongest stimulant of acid secretion. It increases _________ in parietal cells via H2 receptors

Histamine cAMP

________ is characterized by hyperactivity in the intestines; the colon appears hypersensitive to stimulation

IBS

_________ diarrhea results from a reduction in effective surface area reduces absorptive capacity (infection/inflammation)

Impaired absorption/digestion

What is the function of motilin? When is it released? What is it inhibited by?

Increase GI motility During fasting By eating

How do serotonin agonists affect small intestine mobility?

Increase contraction and secretion (treat constipation)

How do opiates affect small intestine mobility?

Increase unproductive contractile activity Decrease secretion (Treatment diarrhea, cause constipation as a serious side effect)

What is the overall effect of parasympathetic innervation of the GI tract?

Increased GI activity

________ bilirubin is unconjugated, while ________ bilirubin is conjugated to glucuronate

Indirect Direct

Fill in the blanks for sialorrhea (excessive salivation): Typically caused by __________ Can be caused by __________ Treatment: __________

Infections/tumors of salivary glands/CNS Some neurological disorders and drugs Muscarinic antagonists (atropine)

Contractions are initiated by intrinsic electrical activity in specialized muscle cells known as __________ They act as _________ cells __________ determines maximum frequency of contraction They initiate waves of depolarization Electrical activity is passed among single-unit smooth muscle cells via _________

Interstitial cells of Cajal Pacemaker Innate depolarization rate Gap junctions

The _________ is the most important phase and accounts for approximately 80% of the pancreatic secretion. This phase produces mainly an _________ secretion

Intestinal phase Enzymatic and aqueous

The _________ results from severe distention, which inhibits contractions in the intestinal area oral to the mass and prevents further movement into area. It is controlled by the ___________.

Intestino-intestinal reflex Sympathetic nervous system

What is the characteristic of endocytosis/pinocytosis involved in absorption in the small intestine?

Invagination of the plasma membrane around the molecule

How do acinar cells regulate the composition of the salivary gland secretions?

Isotonic fluid with composition similar to plasma Cl- actively secreted, all other ions and water passively transported

_________ results from excess bilirubin, which gives a yellow color to the skin and eyes

Jaundice

________ is caused by lactase deficiency, causing lactose to not be absorbed, therefore holding water in the lumen and provoking osmotic diarrhea

Lactose intolerance

How can abnormal acidity in the duodenum cause steatorrhea?

Lipase enzymes are rapidly denatured by acid, therefore the lipids will not be digested Zollinger-Ellison syndrome, cystic fibrosis

What are the causes and symptoms of diverticulitis?

Low-fiber diets and chronic constipation Diverticulitis may occur when fecal material becomes trapped in the pouches Diverticuli can also form fistula with other internal organs (especially the bladder) or perforate, resulting in serious illness Primary symptom is abdominal pain and tenderness

What is the location of smooth muscle in the GI tract?

Lower two-thirds of esophagus to the IAS

During fasting, strong contractions occur at about 90-minute intervals. This is called ___________. The contractions are stimulated by the hormone _________, who's release is regulated by ___________

MMC Motilin The ENS

_________ are waves of electrical activity sweep through the intestines in a regular cycle during fasting They occur every 45-180 minutes during the interdigestive phase (between meals) and is responsible for the ___________

MMC Rumbling experienced when hungry

_________ occur 1-3 times per day and are characterized by the ceasing of segmentation contractions and the disappearance of haustrations. ________ move the material through the large intestine

Mass movements Peristaltic contractions

What is the consequence of Hirschsprung's disease?

Material builds up behind the constriction, leading to expansion of the colon

How is large intestine motility regulated?

Mediated by the ENS Doesn't require the ANS Modulated in strength and frequency by extrinsic input

Describe the sympathetic innervation of the GI system.

Modulate the activity of enteric neurons Directly innervate blood vessels, muscle, and endocrine/secretory cells

_________, a 22-AA peptide, is not a member of the gastrin-CCK family/the secretin-glucagon family It's secreted from the _________ during fasting states It is believed to increase GI motility and, specifically, to initiate the __________ that occur at 90-minute intervals

Motilin Upper duodenum Interdigestive myoelectric complexes

What are the gross structures of the GI tract?

Mouth Esophagus Stomach Small intestine (duodenum, jejunum, and ileum) Large intestine Anus

What is the role of K+ and Cl- in HCl synthesis?

Move into lumen through ion channels (passive diffusion)

How are carbohydrates digested in the small intestine?

Must be broken down into monosaccharides to be absorbed

________ is the second leading cause of gastric ulcers. This is due to inhibition of _________, thus reducing mucus production

NSAIDs PGE1

A large number of neurochemicals/neurocrines have been identified in neurons of the ENS Some of the substances listed are classified as __________ and some are __________ Most neurons of the ENS contain ___________, and upon stimulation, they may co-secrete 2/more neurocrines

Neurotransmitters; Neuromodulators More than 1 neurochemical

What are the 3 phases of swallowing?

Oral phase (voluntary) Movement of food into pharynx by tongue Activation of sensory receptors Pharyngeal phase (involuntary) Initiated by sensory receptors in pharynx Controlled by swallowing center in medulla Respiration inhibited via connections to respiratory center in medulla Esophageal phase (involuntary) Peristaltic wave moves food to the stomach Opens LES and closes the UES Part of swallowing reflex

_________ diarrhea results from accumulation of non-absorbable solutes in the small or large intestine creates osmotic gradient (lactase deficiency)

Osmotic

What is the function of the interstitial cells of Cajal?

Pacemaker cells; set the maximum contraction rate for each region

How can pancreatic insufficiency cause steatorrhea?

Pancreas produces enzymes necessary for fat digestion Pancreatitis/blockage of the ducts

_________ digests TAGs and is secreted in its active form from the pancreas. It requires ______, which binds both to the lipid and to the lipase, providing an anchor.

Pancreatic lipase Co-lipase

What does parasympathetic and sympathetic innervation do to the small intestine motility?

Parasympathetic (acetylcholine): increases motility Sympathetic (norepinephrine): decreases motility

What is the effect of parasympathetic and sympathetic innervation on pancreas secretion?

Parasympathetic: stimulates secretion via the Vagus nerve (acetylcholine) Sympathetic: inhibits pancreatic secretion

Intrinsic factor is secreted by __________. Absence of intrinsic factor results in __________. What is its function?

Parietal cells/glands Pernicious anemia Binds vitamin B12 and the complex is absorbed in the terminal ileum

HCl is secreted by _________. What are its 3 functions?

Parietal cells/oxyntic glands 1. Kills bacteria 2. Activates the protease pepsinogen 3. Breaks down connective tissues in food

How is C. difficile colitis treated?

Patients are treated with specific antibiotics until the C. difficile is eliminated/the normal flora is restored

What are the pathological consequences of good colonic bacteria being replaced with bad colonic bacteria?

Patients undergoing broad-spectrum antibiotic treatment sometimes develop serious GI infections These deadly bacteria are normally kept in check by natural flora C. difficile is the bacteria most associated with serious colitis

The ________ is responsible for activation of mechanoreceptors by pressure and initiation of peristaltic contraction. It is controlled by the _________.

Peristaltic reflex/law of the intestines ENS

_________ cleaves a fatty acid from phospholipids, primarily lecithin

Phospholipase A2

At rest, the sphincters maintain a ___________ that is higher than the pressure in the adjacent organs; thus, at rest, both anterograde and retrograde flow is prevented For GI tract contents to move through the sphincter, it must _________ and transiently lower its pressure

Positive pressure Relax

Although the ENS controls much of the GI tract, note that __________ innervate blood vessels independent of the ENS and this has an important role in controlling GI blood flow In addition, the ANS impacts the __________ involved in GI function, independent of the ENS

Postganglionic sympathetic neurons Accessory organs

Describe the parasympathetic innervation of the GI system.

Preganglionic fibers synapse with ganglion cells of ENS Modulates the activity of the ENS No direct innervation of other GI cells

What are the sympathetic primary neurotransmitters for the GI system?

Preganglionic: acetylcholine acting on nicotinic acetylcholine receptors Postganglionic: norepinephrine

What are the parasympathetic neurotransmitters for the GI system?

Primarily acetylcholine and various peptides

How are proteins digested by the small intestine?

Proteases are released as inactive precursors (zymogens) and are activated by cleavage; the most important proteases are produced by the pancreas

What is the function of gastric mucus?

Protects epithelial cells of stomach

What are the 3 components of gastric motility?

Relaxation of the orad region of the stomach to receive the food bolus from the esophagus Contractions that reduce the size of the bolus and mix it with gastric secretions to initiate digestion (Initiated by intrinsic activity (ENS) and modified by hormones and nervous input) Gastric emptying that propels chyme into the small intestine (The rate of delivery of chyme to the small intestine is hormonally regulated to ensure adequate time for digestion and absorption of nutrients in the small intestine)

What are the accessory organs of the GI tract?

Salivary glands: secretes fluid into the mouth responsible for digestion, lubrication, neutralization, and host defense Pancreas: secretes fluid and enzymes into the small intestine necessary for normal digestion and absorption Liver: produces bile necessary for fat digestion and absorption Gallbladder: stores bile until a meal is consumed

__________ is an autoimmune disease of connective tissue causing lack of propagation of peristaltic wave

Scleroderma

How do duct cells regulate the composition of the salivary gland secretions?

Secreted by: Bicarbonate: makes pH slightly basic compared to plasma K+ Reabsorbed by: Cl- Na+

_________ diarrhea results from excess stimulation of secretory cells (cholera)

Secretory

___________ involves contractions of the circular muscles in the digestive tract, while _________ involves rhythmic contractions of the longitudinal muscles in the gastrointestinal tract; unlike peristalsis, segmentation actually can __________ through the system

Segmentation Peristalsis Slow progression of chyme

_________ occur in the cecum and proximal colon and are responsible for mixing contents and exposing them to absorptive surfaces

Segmentation contractions

_________ is the epithelial layer that faces the blood

Serosa

__________ are a pattern of intrinsic depolarization that occur in the absence of innervation. They are a unique feature of the electrical activity of _________

Slow waves GI smooth muscle

How does flow rate help regulate the composition of the salivary gland secretions?

Slower allows time for duct cells to modify Slower = more different than plasma Exception: bicarbonate increases with flow rate because duct cells are stimulated

Fill in the blanks for the LES: _________ muscle, tonically contracted Prevents _________

Smooth Reflux of gastric contents

________ are specialized regions of circular muscle that separate 2 adjacent regions of the GI tract

Sphincters

By itself, the rectosphincteric reflex is too weak to produce effective defecation and normally combines with __________ mediated through pelvic nerves of the parasympathetic system as well as __________

Spinal reflexes Voluntary muscle control

_______ is excretion of fat in the stool. What are the 4 possible causes?

Steatorrhea 1. Pancreatic insufficiency 2. Abnormal acidity in the duodenum 3. Inadequate bile salts 4. Sequestrants (bile acid resins) reduce the efficiency of bile recycling

Fill in the blanks for the UES: __________ muscle Prevents entry of air into __________ Relaxation controlled by __________

Striated Stomach Swallowing center in the medulla

_________ consists of connective tissue, glands, and large blood vessels. It is found situated between the mucosal layer and the muscularis propria.

Submucosa

What is the treatment of Hirschsprung's disease?

Surgical removal of the affected portion

_________ is initiated voluntarily in the mouth, but thereafter it's under involuntary/reflex control After bolus passes through the UES, the _________ closes the sphincter A __________, also coordinated by the swallowing reflex, travels down the esophagus If the primary peristaltic wave doesn't clear the esophagus of food, a ___________ is initiated by the continued distention of the esophagus The secondary wave, which is mediated by the __________, begins at the site of distention and travels downward

Swallowing Swallowing reflex Primary peristaltic wave Secondary peristaltic wave ENS

What are the symptoms and treatment of scleroderma?

Symptoms Dysphagia, regurgitation, chest pain Treatment Immunosuppressants

What are the symptoms, causes, and treatments of achalasia?

Symptoms Pain (dull), something stuck, regurgitation; nighttime regurgitation can lead to aspiration Causes Nerve degeneration, especially enteric nerves Treatment Reduce contraction: Ca2+ channel block Mechanical disruption: dilation/surgery

Anti-emetics typically target ________. What are 2 examples?

The CTZ 1. Antimuscarinics 2. Antidopaminergics

How is bile synthesis regulated?

The rate limiting enzyme in the biosynthetic pathway, cholesterol 7alpha-hydroxylase, is inhibited by bile salts

How is the LES relaxed?

Ultimately controlled by enteric nerves Swallowing reflex - Vagus nerve VIP (vasoactive intestinal peptide); Neurotransmitter resp. for relaxation (nitric oxide)

What is the role of the H+/K+ ATPase in HCl synthesis?

Uses ATP hydrolysis to transport H+ against its concentration gradient in exchange for K+

_________ is forceful expulsion of intestinal and gastric contents through mouth

Vomiting

What constitutes the aqueous components of the the pancreatic secretions? What is its function?

Water and bicarbonate Neutralizes the acidic contents from the stomach