Unit XII (63-67) - Gastrointestinal Physiology Flashcards
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
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
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
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
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
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
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
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.
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
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
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
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
- 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
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
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
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
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
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
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
List the steps in HCL production by the parietal cell
- H2O + CO2 + carbonic anhydrase = H2CO3 (carbonic acid)
- Carbonic acid dissociates into:
a. H+ - active transport in the apical membrane into the lumen
b. Bicarb - exchanged with Cl in the basolateral membrane - Cl diffuses through the apical membrane into the lumen
- In the lumen H+ + Cl- = HCl
Which of the following hormones stimulates gastric acid secretion? A. Gastrin B. CCK C. Secretin D. Motilin
A. Gastrin
Ref. Guyton 802
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
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
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
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
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
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
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
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
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
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
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
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
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
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
Which of the following ions has higher concentrations in saliva compared to plasma?
a. Calcium
b. Chloride
c. Potassium
d. Sodium
c. Potassium
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
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
Which nerve controls the external anal sphincter?
a. Pelvic nerves
b. Pudendal nerve
c. Myenteric plexus
d. Obturator nerve
b. Pudendal nerve
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.
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
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
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
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
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
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
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
Which of the following hormones inhibits gastric acid secretion? A. Gastrin B. CCK C. Secretin D. Motilin
C.
Ref. Guyton 802
Which of the following causes the GI smooth muscle hyperpolarization? A. Stretch B. Acetylcholine C. Hormones D. Norepinephrine
D. Norepi
Ref. Guyton 799
The rectosphincteric reflex is integrated in the:
a. Brainstem.
b. ENS.
c. Lumbar spinal cord.
d. Sacral spinal cord
D
Cunningham Ch. 28
Pepsin becomes inactivated and has no proteolytic activity above:
a. pH 3
b. pH 5
c. pH 7
d. pH 9
b. pH 5
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
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
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
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
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
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
- 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
Which hormone is released from the G cells, stimulating mucosal growth?
a. Gastrin
b. CCK
c. Secretin
d. GIP
a. Gastrin
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
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
Which of the following hormones stimulates gastric motility? A. Gastrin B. CCK C. Secretin D. Motilin
D. Motilin
Ref. Guyton 802
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
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
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
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
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
Which of the following hormones stimulates insulin release?
a. Cholecystokinin
b. Gastrin
c. Gastric Inhibitory Peptide
d. Motilin
c. Gastric Inhibitory Peptide
- 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
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
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
Which of the following hormones stimulates gallbladder contraction? A. Gastrin B. CCK C. Secretin D. Motilin
B. CCK
Ref. Guyton 802
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
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
- 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
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
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
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
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
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
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.
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
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
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
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
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
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
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
Small intestinal motility is inhibited by which hormone?
a. Secretin
b. Motilin
c. CCK
d. Serotonin
a. Secretin
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
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
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
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
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
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
What are the 2 types of electrical activity in gastrointestinal smooth muscle?
Slow waves
Spikes
Which intestinal cells act as electrical pacemakers?
Interstitial cells of Cajal
How do ion channels in GI smooth muscle differ from nerve cells?
Channels responsible for action potentials predominantly allow calcium ions to enter with a smaller amount of sodium - calcium-sodium channels
Slower to open and close
What factors can alter the resting potential of GI smooth muscle?
Depolarised by:
Stretch
ACh stimulation
Stimulation by GI hormones
Hyperpolarised by:
NEp and Ep
Stimulation of sympathetic nerves
Describe the structure of the enteric nervous system
Myeneteric plexus - between longitudinal and smooth muscle layers - GI movement
Submucosal plexus - in submucosa - secretions and blood supply
Which nerves supply the parasympathetic input to the GIT?
Cranial - vagus
Caudal - pelvic
Where is gastrin secreted?
G cells of stomach
What stimulates gastrin secretion?
Stomach distension
Products of protein digestion
Gastrin-releasing peptide - released during vagal stimulation
What are the actions of gastrin?
Gastric acid secretion
Gastric mucosal growth
Where is CCK secreted?
I cels of duodenum and jejunum
What stimulates CCK secretion?
Digestive products of fat
What action does CCK have?
GB contraction
Inhibits stomach contraction
Inhibits appetite
Where is secretin released?
S cells - duodenum
What stimulates secretin release?
Acidic gastric juice entering duodenum
What are the effects of secretin?
Promotes bicarbonate secretion
Mild effect on motility
Where is glucose-dependent insulinotropic peptide (GIP) released?
K cells of mucosa of upper small intestine
What stimulates GIP release?
Fatty acids and amino acids
What are the effects of GIP?
Slows gastric emptying into duodenum. Reduces secretion of gastric acid
Stimulates insulin secretion
Where is motion secreted?
M cells. Stomach and upper duodenum
What stimulates motion secretion?
Fasting
What is the action of motilin?
Stimulates interdigestive myoelectric complexes
Which GI hormones have a vasodilator effect?
CCK, VIP, gastrin, secretin
What 3 factors increase local GI blood flow?
Hormones
Kinins - kalliidn and bradykinin
Reduced oxygen concentration
What is the main promotor of gastric emptying?
Gastrin
What neurological factors inhibit stomach emptying?
Enterogastric reflex
- directly to stomach through enteric nervous system
- through extrinsic nerves via pre vertebral sympathetic ganglia
- through vagus nerve to brainstem
What factors activate the enterogastric inhibitory reflex?
Distension of duodenum
Irritation of duodenal mucosa
Acidity of duodenal chyme
Osmolality of the chyme
Presence of protein in chyme
What hormone inhibits gastric emptying?
CCK
Secretin and GIP to lesser extent
What hormones increase intestinal peristalsis?
Gastrin, CCK, insulin, motilin, serotonin
What hormones inhibit small intestinal motility?
Secretin and glucagon
What nerves are responsible for a) conscious and c) unconscious control of defecation?
a) Pudendal
b) Pelvic
Are anaerobic/aerobic bacteria more common in the lower intestine?
Anaerobic
What are the predominant cells in the a) body, b) fundus and c) antrum of the stomach?
a) Mucus neck cells, parietal cells, chief cells
b) Enterochromaffin-like cells, somatostatin-producing cells
c) Gastrin and somatostatin-producing cells
What stimulates gastrin release?
Luminal peptides, digested protein, acetylcholine, gastrin-releasing peptide
What stimulates gastric acid secretion?
Gastrin, histamine, acetylcholine
What stimulates somatostatin release? How does it affect the stomach?
pH <3
Reduces gastrin, histamine and acid secretion
What acid-base abnormalities are seen in combination with vomiting?
Metabolic acidosis - most common
Metabolic alkalosis - when gastric outflow/proximal duodenum obstructed
In what situations is metabolic alkalosis recognised in patients with GI signs?
Outflow obstruction, CPV, pancreatitis, gastrinoma
DDX elevated gastrin and low gastric pH?
Gastrinoma
Hepatic/renal disease
How is gastrinoma diagnosed?
Elevated gastrin + low gastric pH
Gastrin measurement following secretin or Ca infusion
How is achlorhydria diagnosed?
Elevated gastrin and gastric pH >3
Pentagastrin or bombesin stimulation
What does a metabolic alkalosis, hypochloraemia, hypokalaemia and acidic urine suggest?
Upper GI obstruction or hypersecretory state
Where are NSAID-related ulcers most often found?
Antrum
How is gastrinoma medically managed?
Omeprazole + somatostatin analogue (eg octreotide)
What is a potential treatment for large gastric ulcers?
Octreotide
Metoclopramie MOA
Antagonises D2-dopaminergic and 5ht3-serotonergic receptors
Cholinergic effect on smooth muscle
Ondansetron MOA
Peripheral 5HT3 antagonism
Maropitant MOA
NK-1 antagonist
What is the risk of maropitant in dogs <8 weeks old
Bone marrow hypoplasia described
What parasites are associated with gastritis? What species do they infect?
Ollulanus Tricuspis - cats
Physaloptera - cats and dogs
How is ollulanus tricuspis spread? How is it diagnosed/treated?
Cat to cat - ingestion of vomitus/autoinfection
Evaluation of gastric juice, vomit or histo
Fenbendazole
What stain is used to confirm pythosis?
Gomori’s methenamine silver
How does gastric pythosis present?
Thickening of gastric outflow tract
How is gastric pythosis treated?
Aggressive resection
Itraconazole and terbinafine for 2-3 months
In which breed has atrophic gastritis been described?
Lundehund
What enzyme is responsible for the majority of carbohydrate digestion?
Pancreatic amylase
Where does the majority of protein digestion occur?
Upper small intestine - pancreatic enzymes
Which cranial nerves are involved in swallowing?
V, IX, X
