GI Physiology Flashcards
(322 cards)
1
Q
adrenergic neurons are typically __________ to gut?
inhibit or stimulatory? Molecule?
A
Inhibitory: adrenaline/epinephrine
2
Q
What is Aldosterone and where is it secreted?
A
Is a steroid hormone (mineralocorticoid) secreted by outer zone glomerulosa of adrenal cortex.
Secreted after low-salt diet, angiotensin, adrenocorticotropic hormone, or high potassium levels.
3
Q
Aldosterone: function
A
act on distal convoluted tubules and collecting ducts of the kidney causing secretion of K+ and reabsorption of Na+ and H2O.
4
Q
What is the GI function of Aldosterone?
A
It stimulates sodium and water reabsorption from the gut and salivary glands in exchange with K+ ions.
Species dependent: water and Na+ reabsorption in proximal colon and decrease absorption in distal colon.
5
Q
Autocrine definition
A
secretions of a given cell modify or regulate functions of the same cell
6
Q
By what process is water absorbed in the small intestine?
A
Entirely by diffusion
7
Q
Where are the 2 CCK receptors located?
A
CCK-1 (CCKA) is primarily found in the GI tract. Its primary fnction is to stimulate bicarb secretion, gall bladder emptying and inhibiting gut motility.
CCK-2 (CCKB) is primarily found on CNS. Its primary function is to regulate nociception, anxiety, memory and hunger.
8
Q
Cholecystokinin: Action
A
Stimulates pancreatic enzyme secretion and gallbladder contractions; inhibits food intake and gastric emptying
9
Q
Cholecystokinin: Production site
A
Duodenum, jejunum, ileum; endocrine I (“i”) cells and enteric neurons of duodenum and jejunum
10
Q
Cholecystokinin: Release stimulus
A
Fats and protein
11
Q
Cholinergic neurons are typically _________ to gut? inhibit or stim? Molecule?
A
stimulatory, Acetycholine
12
Q
Describe the basic electrical rhythm of the stomach.
A
Mixing waves = Slow waves (spontaneous) that result in mixing of the food (chyme), more intense at antrum
13
Q
Discuss the blood flow in the salivary glands.
A
The salivary glands make kalikrein - which when secreted splits a-2 globulin into bradykinin = VASODILATION
14
Q
Discuss the excretion of bilirubin.
A
- RBCs are degraded by reticuloendothelial system (heme + globin) 2. Via heme oxygenase = Biliverdin 3. Unconjugated bilirbin (bound to albumin) 4. In liver conguates with glucuronic acid = Bilirubin glucuronide (80%) and bilirbuin sulfate (10%) = Conjugated bilirubin 5. Conjugated bilirubin is excreted in bile into intestesines 6. In intestines - intestinal bacteria convert it into urobilinogen 7. About 90% of urobilinogen is converted to stercobilinogen then converted to stercobilin and is excreted in feces 8. About 10% of urobilinogen is absorbed into blood and is either recycled to bile (about 95%) or excreted by kidney (about 5%). When urobilinogen is exposure to air in the urine it is converted to urobilin
15
Q
Do the slow waves in the GIT cause muscle contraction?
A
NO! Except in stomach. Provide electrical background to allow AP when excited by intermittent spike potentials (which excites muscle contractions)
16
Q
Does the large intestinal have villi and Crypts of Lieberkuhn?
A
No villi Yes - Crypts of Lieberkuhn
17
Q
During fasting what type of gastric contraction periodically occurs?
A
Migrating myoelectric complexes = mediated by motiliin
18
Q
Explain enterohepatic circulation of bile salts?
A
Bile salts are reabsorbed in SI (diffusion and active transport) → Portal blood → Liver venous sinusoids → Hepatocytes → Bile About 94% of bile salts are recirculated (up to 17x)
19
Q
Five Functions of the gut
A
motility secretion digestion absorption storage
20
Q
Gastric inhibitory polypeptide: action
A
inhibits gastric secretions and emptying and stimulates insulin secretion. Slows movement of ingesta particularly from stomach to intestine.
21
Q
Gastric inhibitory polypeptide: Production site
A
duodenum and jejunum
22
Q
Gastric inhibitory polypeptide: release stimulus
A
fat and glucose (glu. in duodenum)
23
Q
Gastrin & histamine =?
A
Gastrin increases acid secretion indirectly by stimulation of histamine release from ECL which can activate H2 receptors on acid secreting gastric parietal cells.
24
Q
Gastrin binds to ____________
A
CCK-2 receptor, g-protein coupled receptor. Causes stimulation of gastric acid secretion and hyperplasia of enterochromaffin-like cells.
25
Gastrin forms
G-17 (90%) and G-34 (10%, duodenum)
26
Gastrin: Action
Stimulates acid secretion and growth of stomach epithelium (cancer marker)
27
Gastrin: prod. site
stomach (pylorus and antrum) and duodenum G cells
28
Gastrin: Release stimulus
Protein, increased high gastric acidity, gastric distention
29
How are bile salts made?
From cholesterol (diet or made in liver) → 1. cholic acid OR 2. Chenodeoxycholic acid → These combine with either 1. Glycine or 2. Taurine → Conjugated bile salts
30
How are pancreatic enzymes secreted?
Pancreatic enzymes are secreted as zymogens (INACTIVE form) - Such as trypsinogen Once into the small intestine they are activated = Trypsin
31
How are the action potentials different in the GIT?
Calcium-sodium channels = Much slower to open/close = Longer duration of AP
32
How does parasympathetic stimulation affect the ENS?
Increases activity of ENS Mainly vagus nn (some through pelvic nn)
33
How does sympathetic stimulation affect the ENS?
Inhibits GIT activity = From T5-L2 → sympathetic chains → celiac ganglion → mesenteric ganglia (postganglion neuron bodies) → Postganglic fibers to ENTIRE GIT → Secrete norepinephrine (small amounts of epinephrine) Inhibits intestinal smooth muscle, blocks/inhibits neurons in ENS
34
How dot he enterocytes of the Crypts of Lieberkuhn result in formation of a watery vehicle?
1. Active secretion of Cl- 2. Active secretion of HCO3- Drags along Na+ and water
35
How is gastric secretion inhibited?
Food in SI 1. Reverse enterogastric reflex (myeneteric NS, sympathetic NS, vagus n) 2. Food in SI stimulates secretion of SECRETIN and 3 other inhibitors (gastric inhibitory peptide, somatostatin, vasoactive intestinal peptide)
36
How is pepsinogen activated?
Pepsinogen (inactive) is secreted by the peptic/chief cells in the gastric/oxyntic gland. This is converted to pepsin (ACTIVE = highly proteolytic at low pH) when HCl is present
37
How is urea formed in the urine?
Amino Acid + Keto acid (alpha keto-glutoric acid) gets transminated into keto acid + amino acid (glutamic acid) Via oxiative deamination glutamic acid is converted to keto acid + NH3 (ammonia) The ammonia combined with CO2 and creates urea!
38
In general what regulates stomach emptying?
Signals from stomach and duodenum (potent)
39
In the nerve fibers how are AP generated?
By rapid entry of Na into nerve through Na channels
40
Motilin: Action
induction/regulation of phase III of the MMC (migrating motor complex) during fasting (digestive state). Works on both muscles and nerves. Stimulates gastric emptying between meals and secretion of pepsinogen (protein digesting enzyme)
41
Motilin: Production site
M cells of duodenum and jejunum (jejunum lesser extent than duod.)
42
Motilin: Release stimulus
Acetylcholine
43
Name 1 thing that is stimulated and 2 things that are inhibited by gastric inhibitory peptide (GIP)?
Stimulates: 1. Insulin release Inhibits: 1. Gastric motility (mild) 2. Gastric Acid Secretion
44
Name 2 enzymes that aid in starch digestion that are not found in intestinal epithelium.
1. Salivary alpha amylase (Ptyalin) 2. Pancreatic amylase
45
Name 2 mixing movements in the GIT?
1. Peristalsis again sphincter = churning of content 2. Local intermittent constrictive contractions within gut wall (chopping and shearing contents)
46
Name 3 places that protein digestion occurs?
1. Stomach 2. Duodenum/Upper jejunum (pancreatic secretions) 3. Enterocytes (duodenum and jejunum)
47
Name 3 stimuli that result in secretion of cholecystokinin?
1. Protein 2. Fat 3. Acid
48
Name 3 stimuli that result in secretion of gastrin?
1. Protein 2. Distension 3. Nerve (gastrin releasing peptide from vagal stimulation) Acid = Inhibits release
49
Name 3 things that stimulate the secretion of motilin.
1. Fat 2. Acid 3. Nerve
50
Name 4 other functions of the liver in metabolism.
1. Stores Vitamins - A, D, B12 2. Blood coagulation - makes factors (needs Vit K) 3. Storage of iron == Ferritin 4. Metabolizes drugs, hormones, Ca2+, others
51
Name 4 things that are stimulated and 1 thing that is inhibited by secretin.
Stimulates: 1. Pepsin secretion 2. Pancreatic bicarbonate secretion!!! (neutralizes acidic contents) 3. Biliary bicarbonate secretion 4. Growth of exocrine pancrease Inhibits: 1. Gastric Acid secretion
52
Name 6 roles of cholecytsokinin.
Stimulates: 1. Pancreatic enzyme secretion 2. Pancreatic bicarbonate secretion 3. BG contraction 4. Growth of exocrine pancreas Inhibits: 5. Gastric emptying (moderate - time for digestion) 6. Appetite (sensory afferent in duodenum via vagus to appetite centers)
53
Name the 2 primary bile acids.
Cholic acid and chenodeoxycholic acid
54
Name the 4 fat soluble vitamins.
Vitamins A, D, E, K
55
Neurocrine definition
secretion by enteric neurons of neuromodulators or regulatory peptides that affect nearby muscle cells, glands, or blood vessels.
56
Paracrine definition
peptides secreted from cells with subsequent diffusion through the interstitial space to contact and affect other cells
57
Secretin: Action
stimulates HCO3- secretion and inhibits acid secretion (nature's anti-acid). Stimulates exocrine pancreatic and biliary secretions of water, bicarb. gastric mucus and pepsinogen; endocrine pancreatic secretions of insulin, glucagon, and somatostatin; and pancreatic growth Inhibits gastric acid secretion, motility of intestine and gastric mucosal growth.
58
Secretin: production site
duodenum and upper jejunum; S cells
59
Secretin: Release stimulus
Gastric acid, fat, protein, bile acids, and herbal extracts Controlled by action of hormones: CCK, hormonal-neuronal control (CCK-vagal)
60
What 3 locations do carbohydrate digestion occur?
1. Mouth 2. Small intestine (pancreatic secretions) 3. Villi (Brush border)
61
What 3 pancreatic enzymes are responsible for fat digestion?
Pancreatic lipase (fat into FA and monglycerides) Cholesterol esterase (hydrolysis of cholesterol) Phospholipase (FA splits from phospholipids)
62
What 3 pancreatic enzymes are responsible for protein digestion?
1. Trypsin!!!! 2. Chymotrypsin 3. Carboxypolypeptide (can release AA)
63
What 4 components are absorbed via micelles with bile salts?
1. Fatty Acids 2. Monglycerides 3. Cholesterol 4. Other Lipids
64
What accounts for the huge regenerative capacity of the liver?
HGF (Heptocyte growth factor) produced by mesenchymal cells
65
What are 2 main things that are lost in diarrhea?
HCO3- and K+ = Hypercholermic metabolic acidosis
66
What are 2 stimuli for secretion of secretin?
1. Acid 2. Fat
67
What are 3 stimuli for gastric inhibitory peptide (GIP) secretion?
1. Protein 2. Fat 3. Carbohydrates (less)
68
What are essential for emulsification of tryglycerides?
Bile salts and lecithin
69
What are hunger contractions?
When the stomach as been empty for hours - Rhythmic powerful contractions
70
What are slow waves in the GIT?
Rhythmic contractions - determine by frequency of slow waves (NOT AP but slow undulating changes in resting membrane potential) Varies along GIT
71
What are spike potentials in GIT?
True AP - Each time peaks of slow waves temporarily more + spike potentials = Peaks
72
What are the 2 actions of gastrin?
Stimulates: 1. Gastric acid secretion 2. Growth of gastric mucosa
73
What are the 2 duodenal factor that control stomach emptying?
Inhibit Emptying 1. Enterogastric Relfex (food in duodenum inhibit pyloric pump) 2. Hormones = CCK (from jejunal cells that sense fat) = Blocks stomach motility (caused by gastrin)
74
What are the 2 gastric factors that control stomach emptying?
Promote emptying = increased pyloric pump 1. Gastric food volume (stretch) 2. Gastrin release
75
What are the 2 main blood supplies for the liver?
Portal vein and hepatic artery
76
What are the 2 main glands in the SI that result in secretions?
1. Brunner's glands = Mucus and bicarbonate 2. Crypts of Lieberkuhn = Digestive Juices (mucus and watery vehicle)
77
What are the 2 main stimuli for secretion of pepsinogen from peptic/chief cells?
1. Acetylcholine (vagus n. and gastric enetric plexus) 2. Acid in the stomach
78
What are the 2 main ways that proteins are absorbed in the SI?
Via Na+ co-transporter or less by facilitated diffusion
79
What are the 2 major movements in the SI?
1. Mixing contractions = segmentation contractions (from SI distension with chyme) 2. Propulsive Movements = Perstaltic waves Stretch (chyme in duodenum), gastroenteric reflex, hormones (gastrin, CCK, insulin, motilin, serotonin)
80
What are the 2 major movements of the colon?
1. Mixing movements - large circular contractions 2. Propulsion movements = MASS MOVEMENTS (dt gastrocolic and duodenocolic reflexes = distension)
81
What are the 2 reflexes that control defecation and which one is "stronger"?
1. Intrinsic Reflex (local ENS - myenteric plexus) 2. Parasympathetic Defecation Relfex (via pelvic nn) = VERY POWERFUL peristalsis and inhibits internal anal sphincter?
82
What are the 2 types of movement in the GIT?
Propulsive movements (food to move to accommodate digestion/absorptive) 2. Mixing movements (of contents)
83
What are the 2 types of peristalsis during the esophageal phase?
1. Primary peristalsis - continuous wave from pharynx
2. Secondary Peristalsis = from distension of esophagus (controlled by myenteric NS)
84
What are the 2 types of secretions from salivary glands?
1. Serous = Ptyalin (a-amylase) = Digest starch 2. Mucus = Mucin = Lubrication
85
What are the 3 final monosaccharides?
1. Glucose 2. Galatose 3. Fructose
86
What are the 3 main actions that can result in depolarization of smooth muscle cells in GIT?
1. Stretching of muscle 2. Stimulation by acetylcholine release from parasympathetic nn 3. Stimulation by several specific GI hormones
87
What are the 3 main cell types that make of the gastric/oxyntic gland and what do they secrete?
1. Mucous Neck Cell = Mucus 2. Oxyntic/Partiel Cells = HCl, intrinsic factor 3. Peptic/Chief Cells = Pepsinogen
88
What are the 3 main functions of the liver in fat metabolism.
1. High rate of oxidation of fatty acids (fats → glycerol + FFA → Beta oxidation →Acetyl CoA→TCA Cycle or acretoacetic acid 2. Synthesis cholesterol (for bile salts), phospholipids (cell membranes), lipoproteins 3. Convert carbs and proteins into fat
89
What are the 3 main motor functions of the stomach?
1. Storage of food until into SI 2. Mixing of food with gastroc secretions into chyme 3. Slow empyting of chyme from sotmach into SI
90
What are the 3 main stimulators of H+ secretion on parietal cells and what are their receptors?
1. ACh (From Vagus n, M3 receptor) 2. Gastrin (From G cells in antrum, CCKb receptor) 3. Histamine (From ECL cells, H2 receptor)
91
What are the 3 main stimuli for HCl secretion and which cells do these substances stimulate?
1. Acetylcholine = All cells are stimulated 2. Gastrin = Only parietal cells are stimulated 3. Histamine = Only parietal cells are stimulated
92
What are the 3 main stimuli for pancreatic secretion?
1. Acetylcholine 2. Cholecystokinin (CCK) 3. Secretin
93
What are the 3 phases of gastric secretion and how much do they account for acid secretion?
1. Cephalic Phase = 30% acid production 2. Gastric Phase = 60% acid production 3. Intestinal Phase = 10% acid production
94
What are the 3 phases of pancreatic secretion?
Same as gastric secretion 1. Cephalic = 20% pancreatic enzymes 2. Gastric = 5-10% pancreatic enzymes 3. Intestinal: LOTS of pancreatic fluid and bicarbonate (secretin); 70-80% pancreatic enzymes (CCK)
95
What are the 3 phases of swallowing?
1. Voluntary Stage (bolus into pharynx) 2. Pharyngeal Stage (involuntary) 3. Esophageal Stage (involuntary)
96
What are the 3 things in the portal triad?
1. Portal Vein 2. Bile Duct 3. Hepatic Artery
97
What are the 4 main functions of the liver in carbohydrate metabolism?
1. Store glycogen (glucose buffer) 2. Convert galactose/fructose into glucose 3. Gluconeogenesis
98
What are the 4 main functions of the liver in protein metabolism?
1. Deamination of AA 2. Formation of urea 3. Formation of plasma proteins (except Ig) 4. Interconversion of AA
99
What are the 4 steps of Vitamin B12 absorption?
1. Dietary B12 released from pepsin (stomach) 2. Free B12 binds to R protein (from saliva) 3. Duodenum: Pancreatic proteases degrade R protein and Vit B12 transferred to intrinsic factor (prevented from degrading) 4. Vit B12-Intrinsic Factor Complex - Ileum it is transported
100
What are the 6 magic properties of mucus?
1. Adheres tightly to food and spreads thin 2. Sufficient body to coat GIT so that food rarely touches mucosa 3. Causes formation of fecal balls 4. Resistant to digestion by digestive enzymes 5. Particles slide along it easily 6. Amphoteric properties (can buffer acid or alkali)
101
What are the areas that lymph is created/filtrated in the liver lobules?
Within the Space of Disse
102
What are the basic steps in secretion from a glandular cell in the GIT?
1. Diffusion of substance from capillaries into glandular cell 2. Secretory substance made in ER 3. Formed by ribosomes and Golgi 4. Stored Glogi vesicles 5. Increased permeability = Increased intracellular Ca2+ = Vesicles fuse to apical membrane = Exocytosis
103
What are the Brunner's gland stimulated by in the SI?
Result in mucus and bicarbonate secretion Stimulated by: food, vagal stimulation, secretin Result in protection of mucosa in duodenum
104
What are the effects of norepinephrine and epinephrine on GIT nerves (stimulation of smpathetic nn)?
More negative = Hyperpolarized (less excitable)
105
What are the enzymes in the duodenum/upper jejenum that aid in protein digestion?
Pancreatic enzymes: Trypsin. Chymotrypsin, carboxypolypeptidase, proelastase
106
What are the final products of carbodyhrate digestion?
Monosaccarides that are absorbed immediately into portal blood
107
What are the layers of the GI wall?
1. Serosa 2. Longitudinal smooth muscle layer 3. Circular smooth muscle layer 4. Submucosa 5. Mucosa (bundles of smooth muscle fibers)
108
What are the main villus enzymes?
1. Peptidase (peptides → AA) 2. Sucrase, maltase, isomaltase, lactase (dissaccharides → monosaccharides) 3. Intestinal lipase (fats → glycerol and FA)
109
What are the net results of gastric parietal cells?
Net secretion of HCl and net absorption of HCO3- (alkalaine tide that is seen after meals)
110
What are the steps in HCl secretion in a oxyntic/parietal cells?
1. Water dissociates into H+ and OH- in the cytoplasm 2. H+/K+ ATPase allows H+ to be secreted into the canaliculi 3. Potassium in brought into the cell on the basolateral membrane by a Na+/K+ ATPase pump, this makes low intracellular Na+, which brings Na+ into the cell from the canaliculus 4. Pumping out of H+ allows formation of HCO3- since OH- is accumulating in the cell cytoplasm, this is mediated by carbonic anhydrase, this is then secreted in exchange for Cl-, which is sent out into the canaliculus to meet with H+ and make HCl 5. Water passes into the canaliculus by osmosis
111
What are the steps in making bicarbonate in the pancreas?
1. CO2 diffuses into the cell from the blood, combines with water to form carbonic acid (H2CO3), dissociates into H+ and HCO3- 2. H+ is traded in the blood for Na+, which is transported out of the cell with HCO3- 3. This also pulls water by osmosis
112
What are the stimuli for propulsive movements = peristalsis in GIT?
Stimulus = Distenstion (stretching) caused by material Some chemical and physical irritation, strong parasympathetic nervous signals
113
What are the two imperative steps in emptying the GB and what controls this?
Need contraction of GB and relaxation of Sphincter of Oddi (at exit of common bile duct into duodenum) This is stimulated by CCK that is released in response to a fatty meal in the duodenum
114
What are the two layers of muscles in the GIT?
1. Circular muscles 2. Longitudinal muscles
115
What are the two main cells types of the Crypts of Lieberkuhn?
1. Goblet Cells = Mucus 2. Enterocytes = Absorb and secrete water and electrolytes (PURE ECF, alkaline fluid)
116
What are the two main functions of pancreatic secretions?
1. Digestive enzymes 2. Na bicarbonate
117
What are the two main roles of bile salts?
1. Emulsifying or detergent function (decrease surface tension, allows GIT to break down fats) 2. Absorption of micelles into blood (MAJOR effect! = fatty acids, monoglycerides, cholesterol, other lipids)
118
What are the two main roles of bile?
1. Fat digestion and absorption (based on bile acids/salts that aid in emulsifying and absorbing fats) 2. Excretion of waste (including bilirubin and cholesterol)
119
What are the two major glands in the stomach and what do each of them secrete?
1. Oxyntic Gland (Gastric Gland) = HCl, Pepsinogen, intrinsic factor, mucus 2. Pyloric Gland = Mucus, Gastrin
120
What are the two major plexus and what do they control?
1. Myenteric Plexus (Auerbach's): Outer plexus twn longitudinal and circular muscle layers - mainly control GI movements 2. Submucosal Plexus (Meissner's): Inner plexus - controls mainly GI secretions and local blood flow
121
What are the two stages of bile secretion?
1. Bile is secreted by hepatocytes into bile canaliculi 2. Bile flows through ducts to the hepatic duct → common bile duct → duodenum OR cystic duct to Gallbladder Along the way in the ductules/ducts watery Na+ and HCO3- solution secreted by secretory epithelial cells (stimulated by secretin)
122
What are tonic contractions in the GIT?
Continuous (not associated with slow waves) - can last mins to hours These are in addition or instead of rhythmical contractions
123
What causes Ca to enter the muscle fiber to result in a contraction?
Slow waves do NOT cause Ca to enter (ONLY Na), thus no muscle contraction alone During a spike potential (generated by slow waves) = Large amount of Ca enters = muscle contraction
124
What cells are consider the electrical pacemakers for smooth muscle cells?
Interstitial cells of Cajal - Undergo cyclic change in membrane potential Unique ion channels that periodically open = inward pacemarkers currents
125
What cells secrete gastric inhibitory peptide (GIP)?
K cells of duodenum and jejunum
126
What components are in salivary to attack bacteria?
1. Thiocyanate ions 2. Lysozyme 3. Ig
127
What controls stomach emptying?
"Pyloric pump" - intense peristaltic wave in the antrum, pyloric sphincter also controls this
128
What controls the cephalic phase of gastric secretion?
Sight, smell, taste of food → HCl + pepsin release Controlled by: Cerebral cortex (appetite center amygdala and hypothalamus) → Vagus n. → Stomach via Acetylchoine G cells →Gastrin Releasing peptide = GASTRIN release
129
What controls the cephalic phase of pancreatic secretion?
Acetylcholine (vagal n.) = 20% pancreatic enzymes (BUT NO fluid)
130
What controls the gastric phase of gastric secretion?
Food in stomach (stretch) = HCl release Controlled by: Long vagovagal reflex = acetylcholine Local enteric reflex Peptides and AA → G cells → GASTRIN
131
What controls the gastric phase of pancreatic secretion?
Acetylcholine (vagal n.) = 5-10% pancreatic enzymes (BUT NO fluid)
132
What controls the intestinal phase of gastric secretion?
Food in duodenum Controlled by: Enterooxyntic (not gastrin per CVT??)
133
What controls the intestinal phase of pancreatic secretion?
1. Chyme in SI (acid) → Secretin (from S cells in duodenum) → Lots of pancreatic fluid and bicarbonate 2. Food in SI (peptides/fat) → CCK (from I cells in duodenum and upper jejunum) → 70-80% pancreatic enzymes
134
What determines the rate and action potentials and contractions in various segments of GIT?
The frequency of slow waves which is controlled by pacemaker = Interstital cells of Cajal
135
What do neural and hormonal input influence in GIT?
Neural input and hormonal input DO NOT influence the frequency of slow waves, they do influence the frequency of action potentials
136
What do the ECL cells secrete that results in the parietal cells secreting HCl and what controls this process?
Rate and amount of HCL produced is directly related to histamine from ECL cells, which is controlled by GASTRIN
137
What does ECL cells stand for?
Enterochromaffin-Like cell (ECL cell)
138
What does lactase do?
Splits Lactose into galactose and glucose
139
What does maltose and other 3-9 glucose polymers split into?
Glucose by maltase and alpha-dextinase
140
What does motilin do in GIT?
Stimulates gastric and intestinal motility (cyclic release = waves → interdigestive myoelectrical complexes
141
What does sucrose do?
Splits sucrose into fructose and glucose
142
What enzyme is made in pancreatic acini that helps to prevent autodigestions and were is it present?
Trypsin Inhibitor Prevents activation of zymogens in pancreas or ducts or intracellular
143
What enzymes and where are disacchardies hydrolyzed into monosaccharides?
Intestinal Epithelial Enzymes - Within villi in the brush border 1. Maltase 2. Alpha-Dextrinase 3. Lactase 4. Sucrase
144
What happens in the stomach glands between meals?
They make mucus, almost NO acid!
145
What happens to bile when it is stored in the GB?
The bile is concentrated (Water, Na+, Cl- are absorbed through the wall of the GB) - via active transport of Na+ and passive movement of others = Concentration of bile salts, cholesterol. Lecithin, bilirubin
146
What is a reflex that comes from the GIT to spinal cord/brain and then back to GIT?
Defecation reflexes = from colon/rectum to spinal cords and back to produce powerful colon, rectal, and abdominal contractions = Defecation
147
What is a unique feature of the electrical activity of GIT smooth muscle?
Slow waves = Not AP but oscillating depolarization and repolarization
148
What is another name for gastric inhibitory peptide (GIP)?
Glucose-dependent insulinotrophic peptide
149
What is another name for pits?
Crypts of Lieberkuhn = Secretory cells in GIT
150
What is another name for the Na+/glucose cotransporter in the SI?
SGLT 1
151
What is important about the 3 stimuli that result in pancreatic secretions?
The stimuli potentate each other, meaning that pancreatic secretion is greatest with the combined stimuli as compared to single stimuli
152
What is mucus made of?
Water, electrolytes, glycoproteins
153
What is ptyalin?
a-Amylase to digest starches, found in salivary secretions are part of serous secretion
154
What is renointestinal reflex and vesicointestinal reflex?
Inhibits intestinal activity due to kidney or bladder irritation
155
What is splanchnic circulation?
• Blood flow in gut, spleen, pancreas → liver (via portal vein) → hepatic sinusoids (reticuloendothelial cells to remove bacteria, carbs and proteins absorbed) → hepatic veins → vena cava
156
What is the "law" of the gut?
Peristaltic reflex = gut reflexes to result in receptive relaxation (easier propulsion) - Perstaltic waves to the anus
157
What is the accessory pancreatic duct and which species have it?
Opens into duodenum at minor duodenal papilla Dogs = ALWAYS! Cats = Occasionally
158
What is the action potential in GIT dependent on?
Action potentials in GIT cannot occur unless the slow wave brings the membrane potential to threshold
159
What is the colonoileal reflex?
Reflexes from colon to inhibit emptying of ileal contents into colon (reflex from gut to prevertebral sympathetic ganglia back to GIT)
160
What is the driving force behind secretion of HCl from the oxyntic/parietal cells?
H+/K+ ATPase pump on the apical membrane that results in secretion of H+ intot he canaliculus
161
What is the enterogastric reflex?
Signals from colon/small intestines to inhibit stomach motility and secretions (reflex from gut to prevertebral sympathetic ganglia back to GIT)
162
What is the enzyme in the enterocytes that aids in final polypeptide and amino acid digestion?
Peptidases (aminopolypeptidase, dipeptidase)
163
What is the enzyme in the stomach that aid in protein digestion?
Pepsin
164
What is the final composition of saliva and where do these changes take place?
Within the salivary ducts = HIGH K+ and HCO3- (little Na and Cl) 1. K+ active secretion 2. HCO3- secretion 3. Na active absorption 4. Cl- passive absorption (follows Na)
165
What is the final product of fat digestion?
Fatty acids and 2-monoglycerides
166
What is the final product of protein digestion?
Amino Acids
167
What is the function of the myenteric plexus in peristalsis?
If no myenterix plexus (congenital) peristalsis will NOT occur Block it with atropine (affecting cholinergic nn in myenteric plexus)
168
What is the gastrocolic reflex?
Signals from stomach to cause evacuation of colon (reflex from gut to prevertebral sympathetic ganglia back to GIT)
169
What is the gastroielal reflex?
After a meal = increased peristalsis in ileum = emptying
170
What is the main difference btwn the myenteric and submucosal plexuese?
Myenteric Plexus = Linear chain of interconnected neurons that run the length of GIT - Control muscle activity along length of gut Submucosal Plexus = Functions within the inner wall of each segment of intestine, sensory signal from epithelium integrate at submucosal plexus to help control intestinal secretions, local absorption, location contraction of submucosal muscle
171
What is the main electrolyte that is secreted by enterocytes?
Cl- (based on increased cAMP). Na+ and water follow = secretion
172
What is the main mechanism of ion absorption in SI?
Active transport of Na+ Na+ is actively transported from basolateral membrane into interstitial space Low intracellular conc of Na → electrochemical gradient → therefore more Na moves from chyme into enterocyte
173
What is the major component of the Crypts of Lieberkuhn in the large intestine?
MUCUS (some bicarbonate) - Lubrication and hold feces together
174
What is the major site of Na+ absorption in the SI?
Jejunum
175
What is the MOA of PPI, omeprazole?
Inhibit the H+/K+ ATPase on the apical membrane of the gastric parietal cell
176
What is the most important enzyme of fat digestion?
Pancreatic lipase (little by enteric lipase)
177
What is the most important function of pepsin?
Digestion of collagen (to allow digestion of other cellular proteins)
178
What is the name of gastrin secreting tumors?
Zollinger-Ellison Syndrome within the pancreas
179
What is the name of the reticuloendothelial cells in the liver?
Kupffer cells
180
What is the nervous system that is within the wall of the gut?
Enteric Nervous System
181
What is the neurotransmitters that results in excitation in GIT?
Acetylcholine
182
What is the neurotransmitters that results in inhibition in GIT?
Norepinephrine
183
What is the pancreatic duct and which species have it?
Opens within bile duct at major duodenal papilla Dogs = Usually (smaller, but can be absent) Cats = ALWAYS!
184
What is the peritoneointstinal reflex?
irritation of peritonenum = intestinal paralysis
185
What is the primary nerous control of saliva?
Parasympathetic = 2 salivary nuclei in brainstem Stimulated by high centers (appetite) or something on tongue
186
What is the primary secretion from salivary glands?
Either ptyalin or muscus with same electrolyte composition as ECF
187
What is the primary secretion in the esophagus?
MUCUS for Lubrication (simple and compound mucous glands)
188
What occurs in the colonocytes for Na and K?
Na+ absorption (+++aldosterone) K+ secretion
189
What pancreatic enzyme is responsible for carbohydrate digestion?
Pancreatic amylase (starch into disaccharides and trisaccharides)
190
What results in relaxation of stomach during the storage function of the stomach?
Distension with food → “vasovagal reflex” to brain stem → relaxes stomach wall (to accommodate more food)
191
What stimulates the conversion of pepsinogen into pepsin?
HCl
192
What stimulates the release of acetylcholine that results in pancreatic secretions?
Vagus n. and ENS stimulation
193
What stimulates the release of cholecytskinin (CCK) that results in pancreatic secretions?
Released from duodenum and upper jejunum from I cells in response to protein or AA in the lumen
194
What stimulates the release of secretin that results in pancreatic secretions?
Released from duodenum and jejunum in response to acidic content of chyme in the lumen
195
What type of channels control the depolarization and repolarization of the slow waves in GIT?
Ca 2+ open resulting in Ca2+ entering cell = Depolarization K+ open resulting in K+ OUT of cell = Repolarization
196
What would you expect with bilirubin in Cholestasis?
Conjugated bilirubin high
197
What would you expect with bilirubin in hemolysis?
Unconjugated bilirubin high
198
What would you expect with bilirubin in total EHBDO?
NO bilirbin in feces (since no stercobilin stool is light), no urobilin in urine
199
When the G cells in the pyloric glands sense that there is a protein rich meal what occurs?
G cells are stimulated by protein to release GASTRIN into the blood to reach the ECL cells, which when stimulated by gastrin will release HISTAMINE which results in HCL release from the parietal cells
200
Where is cholecystokinin secreted?
I cells of duodenum, jejunum, and ileum
201
Where is gastrin produced?
G cells from antrum, duodenum, jejunum
202
Where is secretin secreted from?
S cells from duodenum, jejunum, ileum
203
Which anal sphincter is under voluntary control?
External anal sphincter
204
Which cell type does the parietal cells in the gastric glands work closely with?
ECL cells
205
Which cell type secretes HCl?
Oxyntic/parietal cells (part of gastric/oxyntic gland)
206
Which cell type secretes intrinsic factor (dog)?
Oxyntic/parietal cells (part of gastric/oxyntic gland)
207
Which cell type secretes pepsinogen?
Peptic/Chief cells (part of gastric/oxyntic gland)
208
Which cells in the pancreas make bicarbonate?
Epithelial cells that line the ductules and ducts Role of bicarbonate is to neutralize acid from stomach chyme
209
Which cells make gastrin?
G cells in the pyloric glands in the distal end of the stomach
210
Which cells secrete motilin?
M cells of stomach, duodenum, jejunum
211
Which enzyme in the brush border in the SI converts trypsinogen into trypsin?
Enterokinase
212
Which hormones control release of pancreatic digestive enzymes?
Vagal stimulation (acetylcholine) Cholecystokinin (CCK)
213
Which hormones control release of pancreatic fluid and bicarbonate?
Secretin
214
Which hormones decreased motility in SI?
Secretin and glucagon
215
Which hormones increased motility in SI?
gastrin, CCK, insulin, motilin, serotonin
216
Which hormones results in secretion of watery Na+ and HCO3- solution from secretory epithelial cells during the second stage of bile secretion?
Secretin!! Which is stimulated by presence of acid within the duodenum
217
Which nerves control the parasympathetic defecation reflex?
Pelvic nn
218
Which nutrient is NOT carried in portal blood and why?
o Fats absorbed from GIT (not carried in portal blood) into intestinal lymphatics to thoracic duct to systemic circulation
219
Which pancreatic enzyme can activate all the other pancreatic enzymes?
Trypsin
220
Which plexus in GIT controls GI movements?
Myenteric Plexus (Auerbach's)
221
Which plexus in GIT controls GI secretions and local blood flow?
Submucosal Plexus (Meissner's)
222
Which secretagogue is the most important in gastric acid secretion?
Histamine!
223
Which transporter is located on the basolateral surface to transport glucose, galactose, and fructose into the blood?
GLUT 2
224
Which transporter on the apical surface allows for facilitated diffusion of fructose?
GLUT 5
225
Why are the directional movements of peristalic waves to the anus?
Can occur in either direction, but orad dies out = likely related to polarization of myenteric plexus
226
Why is neural stimulation of the salivary glands unique?
They are controlled by both parasympathetic and sympathetic NS
227
Why is saliva hypotonic?
Active net solute absorption and salivary ducts are impermeable to water
228
Ptyalin in the saliva hydrolyzes starch into which disaccharide? A. Fructose B. Glucose C. Lactose D. Maltose E. Sucrose
D. Maltose Ref: Guyton, Ch.66 pg. 834
229
Which of the following pancreatic enzymes leads to digestion of proteins into individual amino acids? A. Trypsin B. Carboxypolypeptidase C. Chymotrypsin D. Aminopolypeptidase
B. Ref: Guyton p 835
230
Which of the following is not a potential stimulus for gastric acid secretion? a. Norepinephrine secretion resulting from stimulation of sympathetic nerves. b. Vagal nerve activity resulting from the sight of food. c. The presence of undigested protein in the pyloric antrum. d. Acetylcholine release stimulated by gastric stretch receptors acting on nerves of the ENS. e. Histamine release from cells in the gastric mucosa.
A Cunningham Ch. 29
231
Which gastrointestinal hormone is released in response to digestive products in the intestines and causes gallbladder contraction and release of bile, inhibits stomach contraction, and inhibits appetite? a. Gastric inhibitory peptide b. Cholecystokinin c. Gastrin d. Secretin
b. Cholecystokinin
232
Which of the following is true regarding hydrochloric acid secretion in the parietal cells? a. H+ is secreted from the apical membrane of the parietal cell via facilitated diffusion b. H+-K+ ATPase works at the basolateral membrane to load the parietal cell with hydrogen ions c. Bicarbonate is formed by carbonic anhydrase and transported out of the parietal cell by the bicarbonate chloride cotransporter d. H+ is pumped into the lumen by active transport from a H+-K+ ATPase at the apical membrane of the parietal cell
d. H+ is pumped into the lumen by active transport from a H+-K+ ATPase at the apical membrane of the parietal cell
233
Saliva contains high concentrations of which two ions? a. bicarbonate and sodium b. sodium and chloride c. chloride and bicarbonate d. bicarbonate and potassium
d. bicarbonate and potassium
234
The extrinsic innervation of the gut consists of: a. The enteric nervous system. b. The myenteric and submucosal plexuses. c. Sympathetic (splanchnic) and parasympathetic (vagus) nerves. d. Sympathetic (vagus) and parasympathetic (splanchnic) nerves. e. The pelvic nerve
C Cunningham Ch. 27
235
What are the anatomical differences between the esophagus of dogs, cats and horses?
Dogs, cattle and sheep, its entire length is striated muscle Cats, horses and humans, the proximal esophagus has striated muscle and the distal esophagus smooth muscle.
236
Which of the following hormones stimulates insulin release? A. Gastrin B. CCK C. Gastric Inhibitory Peptide D. Motilin
C. Now known as glucose dependent insulinotrophic peptide Ref. Guyton 802
237
Which of the following are effects of the gastric hormone secretin? a. Stimulation of mucosal endothelial growth b. Promotion of insulin secretion c. Promotion of bicarbonate secretion d. Stimulate gastric acid secretion
c. Promotion of bicarbonate secretion
238
Intrinsic factor must be present in gastric secretions to allow for adequate absorption of vitamin ____ in the ileum. Without intrinsic factor, pernicious anemia can occur. A. B6 B. B12 C. C D. D E. E
B. B12 Ref: Guyton, Ch. 67 pg. 844
239
Inhibition of the enzyme carbonic anhydrase is likely to have what effect on gastric pH? a. Decrease gastric pH b. Increase gastric pH c. Have no effect on gastric pH
B Cunningham Ch. 29
240
3. The term slow waves as applied to the gut refers to: a. Slowly moving fronts of electrical activity that are propagated down the enteric nervous system. b. Slowly moving fronts of electrical activity that result from coordinated changes in cell membrane potential occurring throughout the smooth muscle of the intestinal wall. c. Slowly moving fronts of ingesta that proceed down the intestine in response to peristaltic movement. d. Slowly moving fronts of action potentials that are constantly passing over the gut smooth muscle. e. Slowly moving fronts of peristaltic contractions that pass uniformly over the entire small intestine during the digestive period.
B Cunningham Ch. 28
241
The ____________ reflex occurs as a result of distension of the stomach and duodenum after a meal and is transmitted by way of the autonomic nervous system. a. Defecation b. Enterogastric c. Gastrocolic d. Gastroileal
c. Gastrocolic
242
What factor does not contribute to depolarization of intestinal smooth muscle? a. Stretching of the muscle b. Sympathetic stimulation by norepinephrine release c. Stimulation by several gastrointestinal hormones d. Parasympathetic stimulation by acetylcholine
b. Sympathetic stimulation by norepinephrine release
243
Which of the following causes decreased blood flow to the gastrointestinal tract? A. CCK B. Bradykinin C. Adenosine D. Sympathetic stimulation
D. sympathetic stimulation Ref. 805
244
Which of the following hormones inhibits small intestinal peristalsis? A. Gastrin B. CCK C. Insulin D. Secretin E. Motilin F. Serotonin
D. Secretin Glucagon can also inhibit motility in small intestine Guyton 13th ed Ch. 64
245
Irritation of the peritoneum results in which of the following neurologic reflexes? a. peritoneointestinal reflex – the strong inhibition of excitatory enteric nerves resulting in intestinal paralysis b. peritoneoenteritis reflex - the strong inhibition of excitatory enteric nerves resulting in intestinal paralysis c. peritoneointestinal reflex – the strong excitation of the enteric nervous system inducing hypermotility d. renointestinal reflex - the moderate inhibition of excitatory enteric nerves resulting in intestinal paralysis
a. peritoneointestinal reflex – the strong inhibition of excitatory enteric nerves resulting in intestinal paralysis
246
The enteric nervous system is composed mainly of two plexuses. Which one controls mainly gastrointestinal secretion and local blood flow ? a. Myenteric plexus b. Mucosal plexus c. Submucosal plexus d. Parasympathetic plexus
Answer : c Guyton (12th ed.) p. 755
247
List the steps in HCL production by the parietal cell
1. H2O + CO2 + carbonic anhydrase = H2CO3 (carbonic acid) 2. Carbonic acid dissociates into: a. H+ - active transport in the apical membrane into the lumen b. Bicarb - exchanged with Cl in the basolateral membrane 3. Cl diffuses through the apical membrane into the lumen 4. In the lumen H+ + Cl- = HCl
248
Which of the following hormones stimulates gastric acid secretion? A. Gastrin B. CCK C. Secretin D. Motilin
A. Gastrin Ref. Guyton 802
249
An animal is presented to you with aspiration pneumonia (the result of food material entering the lower respiratory tract). Which of the following lesions would be a likely cause? a. Loss of myenteric plexus function in the pharynx and upper esophagus b. Loss of slow-wave activity in the pharynx and upper esophagus c. A lesion in the brainstem d. A lesion in the trachea e. None of the above
C Cunningham Ch. 28
250
What is the source of the most important signal that regulates gastric emptying? A. Stomach B. Duodenum C. Ileum D. Colon
B. Duodenum Guyton 13th ed p. 811
251
Which of the following is required for normal absorption of cobalamin in the ilium? a) enterokinase b) glucose-dependent insulinotropic peptide c) intrinsic factor d) pepsinogen
Answer C Guyton pg. 844
252
Damage to which of these neurologic structures can result in paralysis of the swallowing mechanism? A. CN V, IX, X, & swallowing center of the brainstem B. CN V, IX, & X C. CN V, VII, & XII D. CN V, IX, X, XII, & swallowing center of the brainstem
Answer D V - trigeminal - sensory to face and motor to m of mastication IX - glossopharyngeal - muscles of swallowing X - vagus - efferent XII - hypoglossal - motor to tongue efferent nerve fibers from swallowing center in the brainstem travel in the facial, vagus, hypoglossal and glossopharyngeal nerves and motor branch of trigeminal Cunningham p 276
253
Which of the following is the most important enzyme for starch digestion? a) Ptyalin b) Pancreatic Amylase c) a-dextrinase d) maltase
B. pancreatic amylase Ptyalin - (also an amylase but just in saliva) Alpha dextrinase - disaccharides Maltase - maltose Guyton pg. 834
254
The myenteric plexus is inhibited by which of the following hormones? A. Gastrin B. CCK C. Secretin D. VIP - vasoactive inhibitory peptide
D. VIP (thought to be but not for sure) Ref. Guyton 800
255
Which cell in the pyloric glands is responsible for secreting histamine in response to stimulation by gastrin? a. Parietal cells b. Chief cells c. Enterochromaffin-like cells d. Goblet cells
c. Enterochromaffin-like cells
256
Which of the following aspects of colon physiology is common to many species, irrespective of interspecies anatomical differences in colon structure? a. Rapid flow of ingesta b. Adaptive relaxation c. Retropulsion, or antiperistalsis d. Haustra formation
C Cunningham Ch. 28
257
Which of the following is characteristic of the inter digestive phase of small intestinal motility? a. Migrating motility complexes consisting of waves of peristaltic contractions that pass over the entire length of the small intestine b. Rhythmic segmentation c. Short waves of peristalsis that die out after a few centimeters d. Complete relaxation of small intestinal smooth muscle
A Cunningham Ch. 28
258
This reflex results when food stretches the stomach allowing for the stomach reducing the tone of the muscular wall a. Vasovagal reflex b. Gastrocolic reflex c. Gastroenteric reflex d. Gastroesophageal reflex
a. Vasovagal reflex
259
Most proteins are absorbed through intestinal epithelial cells in the form of dipeptides, tripeptides, and a few free amino acids. By what mechanism are most absorbed? A. Co-transport B. Facilitated diffusion C. Simple diffusion D. Primary active transport
Answer A. Co-transport Guyton Pg 841
260
Action potentials in the GI smooth muscle are potentiated by the influx of which ion? A. Cl- B. Na C. Ca D. K
C. Ref. 799
261
Parietal cells within the gastric glands release \_\_\_\_\_\_\_\_\_\_, which is needed for absorption of vitamin B12 in the ileum. a. Intrinsic factor b. Hydrochloric acid c. Cortisol d. Histamine
a. Intrinsic factor
262
Which of the following best describes the motility of the proximal region of the monogastric stomach? a. Rhythmic segmentation b. Peristalsis c. Retropulsion d. Adaptive relaxation
D Cunningham Ch. 28
263
Which of the following ions has higher concentrations in saliva compared to plasma? a. Calcium b. Chloride c. Potassium d. Sodium
c. Potassium
264
What factor within the duodenum cannot initiate enterogastric inhibitory reflexes? a. Distension of the duodenum b. Irritation in the duodenal mucosa c. Alkalitity of the duodenal chyme d. Osmolality of the chyme
c. Alkalitity of the duodenal chyme
265
Which one of the following hormones is secreted by K cells? a. Cholecystokinin b. Secretin c. Motilin d. Gastric inhibitory peptide
d. Gastric inhibitory peptide
266
Which nerve controls the external anal sphincter? a. Pelvic nerves b. Pudendal nerve c. Myenteric plexus d. Obturator nerve
b. Pudendal nerve
267
Which of the following accurately describes forward movement of a food bolus through the gastrointestinal tract? A. The swallowing center is located in the medulla and pons of the CNS. B. The movement of a food bolus through the esophagus is passive and only performed by smooth muscle. C. The stomach processes food and has no storage capacity. D. Having hunger pangs (I.e. being "hangry") does not exist, and the stomach does not contract strongly with prolonged emptying.
A. The swallowing center is located in the medulla and pons of the CNS.
268
Which of the following gasses are formed from bacteria in the large intestine? A. Methane, nitrogen, carbon dioxide B. Oxygen, carbon monoxide, methane C. Hydrogen, methane, and carbon dioxide D. Carbon monoxide, methane, hydrogen
Answer C. Hydrogen, methane, and carbon dioxide Guyton Pg 849
269
Which one of the following electrolytes has the highest concentration in bile secreted from the gallbladder? a. Na b. K c. Ca d. Cl
a. Na
270
The main driving force for hydrochloric acid secretion by the parietal cells is… a. H-K ATPase b. Cl-HCO3 antiporter c. Na-K ATPase d. Cl diffusion
a. H-K ATPase
271
Which of the following is most responsible for creating an action potential in gastrointestinal smooth muscle and accounts for the long duration of action potential seen? a. Chloride channels b. Calcium-sodium channels c. Fast sodium channels d. Potassium channels
b. Calcium-sodium channels
272
Which of the following is not a natural ligand for receptors in the pancreas? a. Cholecystokinin b. Acetylcholine c. Gastrin d. Secretin
C Cunningham Ch. 29
273
Chloride is absorbed in which primary locations in the gastrointestinal tract? A. proximal small intestine & ileum B. duodenum C. ileum D. colon
Answer A pg. 839
274
Which of the following cells are considered the pacemakers of the GIT? A. G cells B. Cells of Cajal C. I cells D. K cells
B. Ref. 798
275
Which of the following hormones inhibits gastric acid secretion? A. Gastrin B. CCK C. Secretin D. Motilin
C. Ref. Guyton 802
276
Which of the following causes the GI smooth muscle hyperpolarization? A. Stretch B. Acetylcholine C. Hormones D. Norepinephrine
D. Norepi Ref. Guyton 799
277
The rectosphincteric reflex is integrated in the: a. Brainstem. b. ENS. c. Lumbar spinal cord. d. Sacral spinal cord
D Cunningham Ch. 28
278
Pepsin becomes inactivated and has no proteolytic activity above: a. pH 3 b. pH 5 c. pH 7 d. pH 9
b. pH 5
279
Bile salts have two primary actions, what are they? a. (1) act as a detergent or emulsifying agent to decrease surface tension and (2) facilitate absorption from the intestinal tract b. (1) act as a detergent to increase surface tension and (2) facilitate absorption from the intestinal tract c. (1) induce absorption of food from the gastrointestinal tract and (2) induce digestion of chylomicrons within the lymphatic system d. (1) regulate electrolyte absorption and secretion within the intestinal tract and (2) digest fatty acids
a. (1) act as a detergent or emulsifying agent to decrease surface tension and (2) facilitate absorption from the intestinal tract
280
Glucose is transported into the cell via: A. Facilitated diffusion B. Primary active transport C. Secondary active co - transport D. Secondary active counter transport
C. Secondary active co transport occurs more commonly in GI and renal cells, in all other cells glucose enters the cell via facilitated diffusion. Ref: Guyton p 840
281
Which factor(s) stimulate pepsinogen secretion by the peptic cells ? a. Acetycholine only b. Acetylcholine and gastrin c. Acetylcholine and secretin d. Cholecystokinin only
Answer : a Guyton (12th ed.) p. 779
282
The normal resting membrane potential of gastrointestinal smooth muscle cells is: a. -80 to -90 mV b. -105 to -110 mV c. -50 to -60 mV d. -30 to -40 mV
c. -50 to -60 mV
283
Which of the following can occur as complications to chronic gastritis? I. Achlorhydria II. Ulcerative colitis III. Peptic ulcer IV. Pernicious anemia a) III, IV b) I, IV c) I, III, IV d) I-IV
Answer: c Source: Guyton ed 13, Ch 67, page 844
284
The control of glandular secretion is mostly due to local stimulation in which of the following locations? a. Jejunum b. Salivary c. Rectum d. Pancreas
a. Jejunum
285
1. A unique feature of gastrointestinal (GI) smooth muscle cells is that: a. Their resting transcellular electrical potential has the positive pole on the outside surface of the cell membrane. b. Action potentials, or spikes of membrane depolarization, are not associated with muscle contractions. c. Muscle contractions are stimulated by partial depolarization of the membrane. d. There are spontaneous, rhythmical undulations in the electrical potential across the cell membrane. e. Contraction of the muscles is never influenced by nervous activity.
D Cunningham Ch. 28
286
Which hormone is released from the G cells, stimulating mucosal growth? a. Gastrin b. CCK c. Secretin d. GIP
a. Gastrin
287
Conditions in the duodenum, such as low pH or high fat concentration, can reflexively inhibit gastric emptying. Which reflex arc is involved in this inhibition? a. Parasympathetic nervous system b. GI enteric nervous system c. GI endocrine system d. All the above
D Cunningham Ch. 28
288
The neurotransmitters in the gut are: a. NO and Ach as excitatory, and substance P and VIP as inhibitory. b. NO and Ach as inhibitory, and VIP and substance P as inhibitory. c. NO and VIP as excitatory, and Ach and substance P as inhibitory. d. NO and VIP as inhibitory, and Ach and substance P as excitatory. e. NO and substance P as inhibitory, and Ach and VIP as excitatory.
D Cunningham Ch. 27
289
Which of the following hormones stimulates gastric motility? A. Gastrin B. CCK C. Secretin D. Motilin
D. Motilin Ref. Guyton 802
290
Secretion of gastric inhibitory peptide from the K cells of the duodenum and jejunum is stimulated by protein, fat, and carbohydrates. What does secretion of gastric inhibitory peptide stimulate? a. Insulin release b. Gastric acid secretion c. Pepsin secretion d. Biliary bicarbonate secretion
a. Insulin release
291
Which of the following is secreted by activated salivary cells and is important in enzymatic formation of bradykinin? a. cAMP b. Kallikrein c. Secretin d. Pepsin
b. Kallikrein
292
In what specific location in the gastrointestinal tract is the intestinal phase of gastric secretion initiated? a. Stomach b. Duodenum c. Ileum d. Jejunum
b. Duodenum
293
Cholecystokinin and gastrin: a. Share all of the same receptors. b. Share CCK1 receptors. c. Share CCK2 receptors. d. Share gastrin I receptors. e. Share gastrin II receptors
C Cunningham Ch. 27
294
Which of the following correctly describes the secretion or action of secretin? a. Secretion is mainly stimulated by the presence of carbohydrates in the duodenum b. Secreted from the stomach c. Decreases stomach acid production d. Secretin’s main effect is increasing intestinal motility
c. Decreases stomach acid production
295
Which of the following hormones stimulates insulin release? a. Cholecystokinin b. Gastrin c. Gastric Inhibitory Peptide d. Motilin
c. Gastric Inhibitory Peptide
296
2. The interstitial cells of Cajal are: a. Modified neurons capable of generating contraction. b. Modified neurons capable of generating only action potentials. c. Modified neurons capable of generating only slow waves. d. Modified smooth muscle cells capable of generating only slow waves. e. Modified smooth muscle cells capable of generating only action potentials.
D Cunningham Ch. 28
297
Colonic “pacemakers”: a. Are anatomically distinct structures composed of specialized smooth muscle cells. b. Shift in their sites under the influence of the ENS. c. Are involved in segmentation, but not peristalsis. d. Control defecation.
B Cunningham Ch. 28
298
The cholera toxin specifically targets which area of the gastrointestinal tract? a. duodenum b. duodenum, jejunum, and ileum c. distal ileum and colon d. colon only
C. Distal Ileum and Colon (location of crypts of liberkun) The enterocytes in these crypts are responsible for water secretion toxin --\> increase cAMP --\> Cl channels open --\> Cl loss activates Na pump--\> Na into lumen --\> H2O follows Na --\> excess water loss --\> diarrhea Guyton p. 846
299
Which of the following hormones stimulates gallbladder contraction? A. Gastrin B. CCK C. Secretin D. Motilin
B. CCK Ref. Guyton 802
300
Which of the following reflexes occurs as a result of chyme entering the duodenum? a. gastroileal reflex b. gastroenteric reflex c. mienteric reflex d. viscointestinal reflex
b. gastroenteric reflex
301
Which enzyme is most active at a pH of 2.0 to 3.0 and plays an important role in digesting collagen? a. Alpha dextrinase b. Amylase c. Pepsin d. Elastase
Answer: C. Reference: Guyton Ch. 66 Pg. 835
302
3. Which of the following reactions in the liver could be expected to occur during both the digestive phase and a prolonged fast? a. Glycogen synthesis b. Fatty acid synthesis c. Ketone body synthesis d. Ketone body oxidation e. Triglyceride synthesis from fatty acids
E Cunningham Ch 32
303
Lower esophageal achalasia is secondary to damage of: A. Myenteric plexus B. Lower esophageal sphincter C. Cranial nerve X D. Meissner’s plexus
A. The myenteric plexus aka auerbach's plexus is located in between the longitudinal and circular muscle layers and control movement through the entire GIT. The submucosal aka meissner's plexus controls local secretion and blood flow Ref: Guyton p 843
304
Which cell type acts as the electrical pacemaker for the smooth muscle of the gastrointestinal tract? a. Epithelial cells of Cajal b. Enteric nervous plexus c. Enteric purkinje fibers d. Interstitial cells of Cajal
d. Interstitial cells of Cajal
305
The functions of the GI tract are mainly controlled by: a. The central nervous system. b. The enteric nervous system. c. The endocrine system. d. The enterochromaffin system. e. The hormonal and central nervous systems.
B Cunningham Ch.27
306
In the small intestine, sodium is mainly reabsorbed in the APICAL border of epithelial cells by which protein? a) Na+/K+ ATPase pump b) Na+ and substrate co-transporters c) Na+ leak channel d) Na+/Cl- antiporter
B. Na and substrate co-transporters ie. aa, glucose vs the basolateral membranes in which Na/K pump regulates Na transport. Source: Guyton ed 13, Ch 66, page 838
307
How long does it take for aldosterone to take effect and increase sodium absorption in the intestine? A. 1-3 hours B. 3-6 hours C. 6-9 hours D. 9-12 hours
Answer A. 1-3 hours Cl and H2O follow Na Guyton Pg 839
308
At the level of the salivary gland, what happens with the following ions? A. Sodium is passively absorbed, chloride is actively absorbed, potassium is actively secreted, and bicarbonate is secreted. B. Sodium is actively secreted, chloride is passively secreted, potassium is actively absorbed, and bicarbonate is secreted. C. Sodium is actively absorbed, chloride is passively absorbed, potassium is actively secreted, and bicarbonate is secreted. D. Sodium is actively secreted, chloride is passively secreted, potassium is passively secreted, and bicarbonate is absorbed.
C. Sodium is actively absorbed, chloride is passively absorbed, potassium is actively secreted, and bicarbonate is secreted.
309
The term cephalic phase is used in reference to a number of activities occurring in the GI tract. In general, the term means: a. The early phases of digestion, when food is nearest the head. b. Any actions stimulated directly by the presence of food in the stomach. c. Any actions stimulated directly by the presence of food in the mouth. d. Digestive events stimulated by the presence of food in the GI tract, but requiring reflexes integrated in the CNS e. Digestive events that occur before the ingestion of food and in response to central nervous system stimulation that is brought on by the anticipation of eating.
E Cunningham Ch. 28
310
Which of the following does not play a role in regulating pancreatic secretions? A. Secretin B. CCK C. Ach D. Pepsinogen
D. Pepsinogen (stimulates acid secretion in the stomach) Secretin - stimulates bicarb secretion by pancreas in response to acid in SI CCK - stimulate bicarb and pancreatic enzyme in response to food in SI Ach - excitatory neurotransmitter Guyton 13th ed. p 826
311
At which site in the gastrointestinal tract do peptic ulcers most commonly occur? a. Lesser curvature b. Greater curvature c. Gastric cardia d. Pylorus
Answer: D. Reference: Guyton Ch. 67 Pg. 844; Fig 67-1
312
Which of the following is an important action of cholecystokinin? a. Inhibit gastric acid secretion b. Mucosal growth c. Intestinal motility d. Stimulate pancreatic enzyme secretion
d. Stimulate pancreatic enzyme secretion
313
In monogastric animals, saliva produced during periods of rapid secretion has a higher electrolyte concentration than saliva produced during periods of slow salivary secretion. From your understanding of salivary gland physiology, which appears to be the most likely explanation? a. During periods of slow salivary secretion, the acinar cells are inactive, and low-electrolyte saliva is secreted by the duct cells. b. Parasympathetic stimulation of the acinar cells results in the elaboration of a more electrolyte-rich saliva. c. Gastrin stimulation increases the electrolyte concentration of saliva. d. During rapid secretion, fluid produced by the acinar cells is exposed to the actions of the duct cells for a shorter time than during slow rates of secretion. e. Different cell types within the acinus are responsible for salivary production, depending on the type of stimulus.
D Cunningham Ch. 29
314
Which of the following factors inhibit gastric emptying by initiating enterogastric inhibitory reflexes ? a. Increased pH of the chyme b. Irritation of the duodenal mucosa c. Stretching of the stomach wall d. Decreased filling of the duodenum
Answer : b Guyton (12th ed.) p. 767
315
The arrangement of smooth muscle fibers in the muscular layer of the intestinal wall is best described as: a. inner longitudinal and outer circular smooth muscle layers b. inner circular and outer longitudinal smooth muscle layers c. single layer of circular smooth muscle d. two layers of circular smooth muscle, separated by a nerve plexus
b. inner circular and outer longitudinal smooth muscle layers
316
Small intestinal motility is inhibited by which hormone? a. Secretin b. Motilin c. CCK d. Serotonin
a. Secretin
317
The pathophysiologic basis of which of the following conditions is associated with damage to the myenteric plexus? A. Pancreatitis B. Achlasia C. Achlorydia D. Gastritis
B. Achalasia is a condition in which the lower esophageal sphincter fails to relax during swallowing. Pathophysiological studies have shown damage in the neural network of the myenteric plexus of the lower two thirds of the esophagus, which causes spasticity of the musculature of the lower esophagus. As a result, the lower portion of the esophagus fails to undergo receptive relaxation as the bolus of food approaches this area after swallowing. pp. 845-846
318
In achalasia, damage to which structure in the lower esophagus results in failure of the gastroesophageal sphincter to relax during swallowing ? A. Myenteric plexus B. Submucosal plexus C. Esophageal mucosa D. Esophageal musculature
Answer A Guyton (12th ed.) p. 799
319
During sodium absorption by glucose co-transport: a. Chloride is absorbed by the paracellular route. b. Chloride absorption is not affected. c. Chloride is absorbed in exchange for bicarbonate. d. Chloride absorption is coupled with potassium absorption. e. Chloride is absorbed in exchange for hydrogen ion
A Cunningham Ch 30
320
Entry of food into the small intestine leads to secretion of which of the following substances important for stimulating pancreatic secretion? a. Cholecystokinin b. Vasoactive intestinal peptide c. Acetylcholine d. Secretin
a. Cholecystokinin
321
Rate of digestion is dependent upon which one of the following? a. Total surface area available to digestive enzymes b. Increased sympathetic nervous system stimulation c. Total volume of bile secreted into the proximal duodenum d. Diameter of the pyloric sphincter
a. Total surface area available to digestive enzymes
322
From luminal to serosal layers, which of the following is the appropriate order in which the layers of the gastointestinal tract occur? A. Epithelium --\> mucosa --\> mucosal muscle --\> sub mucosa --\> longitudinal muscle -\> circular muscle -\> serosa B. Mucosa --\> epithelium --\> mucosal muscle --\> sub mucosa --\> circular muscle -\> longitudinal muscle -\> serosa C. Epithelium --\> mucosa --\> submucosa --\> mucosal muscle --\> circular muscle -\> longitudinal muscle -\> serosa D. Epithelium --\> mucosa --\> mucosal muscle --\> sub mucosa --\> circular muscle -\> longitudinal muscle -\> serosa
D. Epithelium --\> mucosa --\> mucosal muscle --\> sub mucosa --\> circular muscle -\> longitudinal muscle -\> serosa
