BRS - GASTROINTESTINAL PHYSIOLOGY EXAM
QUESTIONS AND ANSWERS VERIFIED
What is the function of epithelial cells of the GI tract?
secretion and absorption
What is the function of the muscularis mucosa?
change the surface area fro secretion and absorption
What is the function of circular muscle?
decrease lumen diameter
What is the function of longitudinal muscle?
shortening of GI tract
What two major plexuses constitute the enteric nervous system?
Submucosal (Meissner's) plexus and myenteric (Auerbach's) plexus
Is the parasympathetic nervous system usually excitatory or inhibitory with
respects to the GI tract?
excitatory
Where do preganglionic parasympathetic fibers synapse?
myenteric and submucosal plexuses
Which nerves carry the parasympathetic stimulation?
vagus and pelvic nn.
What does the vagus n. innervate with respects to the GI tract?
esophagus, stomach, pancreas, small intestine, and upper large intestine
,What is the name of both afferent and efferent reflexes carried in the vagus
nerve?
vasovagal reflexes
What does the pelvic nerve innervate with respects to the GI tract?
lower large intestine, rectum, and anus
Is the sympathetic nervous system usually inhibitory or excitatory with respects
to the GI tract?
inhibitory
Where do sympathetic fibers for the GI tract originate?
T8-L2
Where do postganglionic sympathetic fibers synapse?
myenteric and submucosal plexuses
What provides the intrinsic innervation of the GI tract in general?
enteric nervous system
What type of reflexes are used in the enteric nervous system?
local reflexes
Can the enteric nervous system control most functions of the GI tract without
extrinsic innervation?
Yes
The myenteric (Auerbach's) plexus is involved in what type of control primarily?
motility
The submucosal (Meissner's) plexus is involved in what type of control primarily?
secretion and blood flow
, What four substances meet the requirements to be "official" GI hormones?
gastrin, cholecystokinin, secretin, and glucose-dependent insulinotropic peptide
What part of gastrin gives it its biological activity?
the last four amino acids of the C-terminal
What are the actions of gastrin?
increase proton secretion from parietal cells; stimulate growth of gastric mucosa
What cells in the antrum secrete gastrin?
G cells
What are the stimuli for secretion of gastrin?
1. small peptides and amino acids
2. stomach distention
3. vagal stimulation mediated by gastrin-releasing peptide (GRP)
Why does atropine not block vagally mediated gastrin secretion?
Atropine is a competitive inhibitor of muscarinic receptors, but since GRP is released in
addition to ACh, secretion continues.
What inhibits gastrin secretion?
negative feedback by protons; somatostatin
Is cholecystokinin (CCK) homologous to gastrin?
yes; five C-terminal amino acids are the same in gastrin and CCK
Where does the biological activity of CCK reside?
C-terminal heptapeptide
True or False? Due to homology between CCK and gastrin, the C-terminal
heptapeptide has both gastrin and CCK activity?
QUESTIONS AND ANSWERS VERIFIED
What is the function of epithelial cells of the GI tract?
secretion and absorption
What is the function of the muscularis mucosa?
change the surface area fro secretion and absorption
What is the function of circular muscle?
decrease lumen diameter
What is the function of longitudinal muscle?
shortening of GI tract
What two major plexuses constitute the enteric nervous system?
Submucosal (Meissner's) plexus and myenteric (Auerbach's) plexus
Is the parasympathetic nervous system usually excitatory or inhibitory with
respects to the GI tract?
excitatory
Where do preganglionic parasympathetic fibers synapse?
myenteric and submucosal plexuses
Which nerves carry the parasympathetic stimulation?
vagus and pelvic nn.
What does the vagus n. innervate with respects to the GI tract?
esophagus, stomach, pancreas, small intestine, and upper large intestine
,What is the name of both afferent and efferent reflexes carried in the vagus
nerve?
vasovagal reflexes
What does the pelvic nerve innervate with respects to the GI tract?
lower large intestine, rectum, and anus
Is the sympathetic nervous system usually inhibitory or excitatory with respects
to the GI tract?
inhibitory
Where do sympathetic fibers for the GI tract originate?
T8-L2
Where do postganglionic sympathetic fibers synapse?
myenteric and submucosal plexuses
What provides the intrinsic innervation of the GI tract in general?
enteric nervous system
What type of reflexes are used in the enteric nervous system?
local reflexes
Can the enteric nervous system control most functions of the GI tract without
extrinsic innervation?
Yes
The myenteric (Auerbach's) plexus is involved in what type of control primarily?
motility
The submucosal (Meissner's) plexus is involved in what type of control primarily?
secretion and blood flow
, What four substances meet the requirements to be "official" GI hormones?
gastrin, cholecystokinin, secretin, and glucose-dependent insulinotropic peptide
What part of gastrin gives it its biological activity?
the last four amino acids of the C-terminal
What are the actions of gastrin?
increase proton secretion from parietal cells; stimulate growth of gastric mucosa
What cells in the antrum secrete gastrin?
G cells
What are the stimuli for secretion of gastrin?
1. small peptides and amino acids
2. stomach distention
3. vagal stimulation mediated by gastrin-releasing peptide (GRP)
Why does atropine not block vagally mediated gastrin secretion?
Atropine is a competitive inhibitor of muscarinic receptors, but since GRP is released in
addition to ACh, secretion continues.
What inhibits gastrin secretion?
negative feedback by protons; somatostatin
Is cholecystokinin (CCK) homologous to gastrin?
yes; five C-terminal amino acids are the same in gastrin and CCK
Where does the biological activity of CCK reside?
C-terminal heptapeptide
True or False? Due to homology between CCK and gastrin, the C-terminal
heptapeptide has both gastrin and CCK activity?
