Section IV: Physiology of the Gastrointestinal Tract

Question 1

Chapter 27 Regulation of Gastrointestinal Function

Which statement is the most accurate anatomical description of the enteric nervous system (ENS) of the gut?

a. Intrinsic neuronal fibers and their cell bodies are diffusely spread throughout the length and thickness of the stomach
and intestine.
b. Intrinsic neuronal fibers traverse the length of the stomach and intestine in discrete nerve bundles.
c. Intrinsic neuronal cell bodies are aggregated in a discrete “gut brain” that is positioned near the pylorus.
d. Intrinsic neuronal cell bodies lie in discrete planes within the thickness of the gut wall and are diffusely distributed
throughout its length.
e. Intrinsic neuronal fibers exist only in the longitudinal muscle layer of the stomach and intestine

Answer 1

D

Question 2

Which statement is true with regard to the parasympathetic fibers that innervate the cells of the ENS?

a. The fibers exit the central nervous system from lumbar segments of the spinal cord.
b. The fibers have vasoactive intestinal peptide as a neurotransmitter.
c. The fibers are inhibitory.
d. The fibers are preganglionic.
e. There are no parasympathetic fibers that innervate cells of the ENS

Answer 2

D

Question 3

Which statement is true with regard to the GI endocrine cells?

a. Secretory activity is influenced by the luminal contents of the gut.
b. Hormones are secreted directly into the gut lumen and affect the activity of glands “downstream” from the point of secretion.
c. The secretory products of the GI endocrine cells are steroid hormones.
d. Each GI endocrine cell can produce many different types of hormones, depending on the stimulus applied to it.

Answer 3

A

Question 4

Which of the following statements concerning the neurohumoral regulatory molecules of the gut is true?

a. They are all peptides.
b. They all are excitatory and increase the rate of gut motility and secretion.
c. GI neurohumoral regulatory molecules and their analogs and antagonists will probably become important agents
of therapy in GI disease.
d. All the above

Answer 4

C

Question 5

Which of the following conditions in the gut would NOT provide direct sensory input to the ENS?

a. Changes in luminal pressure resulting in changes in tension of gut wall musculature.
b. Changes in luminal pH.
c. Changes in luminal osmotic pressure.
d. Changes in the rate of ingesta flow

Answer 5

D

Question 6

Which of the following neurocrine transmitter molecules is most consistently excitatory relative to gut functions?

a. Somatostatin
b. Acetylcholine
c. Vasoactive intestinal peptide (VIP)
d. ATP

Answer 6

B

Question 7

All neurocrine transmitter molecules are peptides.

a. True
b. False

Answer 7

B

Question 8

The conscious sensation of pain due to excessive distention of a segment of the gut arises from afferent impulses traveling to the brain through:

a. The myenteric plexus
b. The submucosal plexus
c. The vagus nerve
d. The splanchnic nerves

Answer 8

D

Question 9

Which anatomical description best applies to the organization of the GI endocrine cells?

a. Cells arranged into small islets in the intestinal
submucosa.
b. Cells distributed diffusely throughout the mucosa of the GI tract.
c. Cells arranged into discrete glands situated between the circular and longitudinal muscle layers.
d. Cells distributed diffusely throughout the submucosa of the GI tract

Answer 9

B

Question 10

The influence of the GI mucosal immune system on gut functions is mediated by:

a. The CNS.
b. The direct action of cytokines on gut smooth muscle and glands.
c. The interaction of cytokines with the ENS and GI
endocrine/paracrine cells.
d. The direct action of T cells on gut smooth muscle and glands

Answer 10

C

Question 11

Chapter 28 Motility Patterns of the Gastrointestinal Tract

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

Answer 11

D

Question 12

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.

Answer 12

D

Question 13

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.

Answer 13

B

Question 14

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

Answer 14

C

Question 15

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 central nervous system.
e. Digestive events that occur before the ingestion of food and in response to central nervous system stimulation brought on by the anticipation of eating.

Answer 15

E

Question 16

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

Answer 16

D

Question 17

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

Answer 17

D

Question 18

Which of the following is characteristic of the interdigestive 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

Answer 18

A

Question 19

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

Answer 19

C

Question 20

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.

Answer 20

B

Question 21

The rectosphincteric reflex is integrated in the:

a. Brainstem
b. ENS
c. Lumbar spinal cord
d. Sacral spinal cord

Answer 21

D

Question 22

Chapter 29 Secretions of the Gastrointestinal Tract

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 the duct cells secrete low-electrolyte saliva.
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.

Answer 22

D

Question 23

Some nutritionists are experimenting with a drug that increases salivary secretion in cattle. What effect do you think this would have on rumen pH?

a. Increase rumen pH
b. Decrease rumen pH
c. Have no effect on rumen pH

Answer 23

A

Question 24

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

Answer 24

B

Question 25

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.

Answer 25

A

Question 26

Which of the following is *not* a natural ligand for receptors in the pancreas? a. Cholecystokinin b. Acetylcholine c. Gastrin d. Secretin

Answer 26

C

Question 27

# Chapter 30 Digestion and Absorption: The Nonfermentative Processes Finding triglycerides and starch in the feces of a thin dog with a normal feed intake would suggest: a. Malabsorption b. Maldigestion

Answer 27

B

Question 28

Which statement about the tight junctions is false? a. Tight junctions encircle the enterocyte near its apical end. b. Tight junctions form the dividing line between the apical membrane and the basolateral membrane. c. Tight junctions are impermeable to water. d. Tight junctions separate the lateral space from the intestinal lumen. e. Tight junctions are the only points that attach enterocytes together.

Answer 28

C

Question 29

Which of the following molecules is consumed during the process of hydrolytic digestion? a. Glucose b. Alanine c. Dipeptides d. Fatty acids e. Water

Answer 29

E

Question 30

A drug that blocks the activity of the Na+,K+ -ATPase pump could be expected to have what effect on sodium-glucose cotransport? a. Increased sodium-glucose cotransport b. Decreased sodium-glucose cotransport c. No effect on sodium-glucose cotransport

Answer 30

B

Question 31

During sodium absorption by glucose cotransport: 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.

Answer 31

A

Question 32

Before entering the intestinal capillaries, all nutrients pass through the: a. Apical membrane b. Tight junction c. Lateral space d. Basolateral membrane e. Enterocyte cytoplasm

Answer 32

C

Question 33

# Chapter 31 Digestion: The Fermentative Process In which of the following respects is fermentative digestion *different* from glandular digestion? a. Enzymes are not involved in fermentative digestion. b. Chemical bonds are not split by hydrolysis in fermentative digestion. c. Only carbohydrates are digested by fermentative digestion. d. Substrates are more extensively altered in fermentative digestion than in glandular digestion. e. Proteins are digested to amino acids by fermentative digestion and to dipeptides by glandular digestion

Answer 33

D

Question 34

In a comparison of hindgut fermentation and forestomach fermentation, which of the following statements is true? a. The microbial populations are considerably different, but the products of digestion are the same. b. The microbial populations are the same, but the products of digestion are considerably different. c. Both the microbial populations and the digestion products are similar. d. Structural carbohydrates of plants are not digested by hindgut fermentation. e. A nitrogen source is not required by the microbes of the hindgut

Answer 34

C

Question 35

The three VFAs—acetate, propionate, and butyrate—are: a. Net-reaction products of the fermentative action of the entire rumen biomass. b. The individual products of cellulose, starch, and hemicellulose digestion, respectively. c. The individual products of bacterial, protozoal, and fungal digestion, respectively. d. Volatile products that leave the rumen with the gas phase during eructation. e. Intermediate metabolites that are passed between microbial species.

Answer 35

A

Question 36

Matching protein and energy availability in the rumen is an important nutritional goal in feeding ruminants. Which of the following completions of this statement concerning protein and energy availability in the rumen is false? Diets well matched in available protein and energy result in a. The most efficient use of energy for microbial growth. b. Maximal delivery of protein to the host. c. Minimal breakdown of protein in the rumen. d. Loss of a minimal amount of dietary amino acids because of formation of excess ammonia. e. Optimal rumen ammonia concentrations

Answer 36

C

Question 37

Which of the following statements is true of both methane and propionate? a. They are waste products of anaerobic fermentation but contain potential energy that is recoverable by the host. b. They are highly oxidized molecules. c. They are eructed from the rumen. d. Their formation results in the generation of NAD from NADH. e. They are toxic to monogastric animals.

Answer 37

D

Question 38

# Chapter 32 Postabsorptive Nutrient Utilization ll the following are metabolites that can be oxidized for fuel in the animal body. Which one is not important in the transport of energy between organs and organ systems? a. Triglyceride b. Ketone bodies c. Oxaloacetic acid d. Nonesterified fatty acids e. Amino acids

Answer 38

C

Question 39

Which of the following reactions is not characteristic of the absorptive phase of digestion? a. Hepatic synthesis of glycogen b. Hepatic uptake of glucose c. Destruction of dietary amino acid d. Utilization of muscle-derived amino acid for gluconeogenesis e. Hepatic synthesis of triglyceride from glucose

Answer 39

D

Question 40

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

Answer 40

E

Question 41

Which of the following statements is true of both ketone bodies and nonesterified fatty acids? a. They are water soluble. b. They provide energy for muscle metabolism. c. They circulate in blood bound to albumin. d. They can provide energy to the brain. e. They are formed exclusively in the liver.

Answer 41

B

Question 42

Which of the following amino acids is not extensively catabolized by the liver? a. Valine b. Alanine c. Glutamine d. Asparagine e. Glycine

Answer 42

A