Neuroendocrine Control Flashcards
what is the ENS also known as?
second brain
ENS samples the gut content through…
receptors
how do ENS neurons connect to other neurons both inside and outside the ENS?
interneurons and afferent neurons
what do efferent ENS neurons innervate?
target cells
smooth muscle, secretory, absorptive cells
ENS influences ___ organs and the ___
neighboring organs
brain
is the ENS able to still coordinate digestion if it’s severed from the brain?
YES
in monogastrics
what is of fundamental significance to control of motility and secretion?
detecting nutrients in GI tract
what type of cell senses macronutrients?
L cells
has microvilli that make direct contact with nutrient
afferent neurons of the ENS are ___ neurons
cholinergic
afferent neurons N receptors in the….
mucosa - chemoreceptors and mechanoreceptors
muscle layer - mechanoreceptors
explain what’s going on in this image
example of afferent neuron function
a lot of the sensory info from the gut also reaches…
brain
which hormones/substances are part of the excitatory process of ENS?
ACh
substance P
which hormones/substances are part of the inhibitory process of ENS?
VIP
NO
ATP
what do the excitatory efferent neurons do to the ENS?
contract longitudinal and sphincter smooth muscles
stim secretion
degranulate enteroendocrine cells
what do the inhibitory efferent neurons do to the ENS?
inhibit smooth muscle cells
stim secretion
cause vasodilation
what is the myenteric plexus?
N longitudinal and circular smooth muscle layers
control gut movement
what is the submucosal plexus?
N glandular epithelium, intestinal endocrine cells, submucosa blood vessels
controls intestinal secretion
myenteric plexus is also known as…
Auerbach’s plexus
submucosal plexus is also known as…
Meissner’s plexus
the myenteric plexus is mainly concerned with ____, whereas the submucosal plexus is concerned with ___
myenteric - gut movement
submucosal - control secretions
what do interneurons do?
help integrate extrinsic and intrinsic input
communicates between myenteric and submucosal plexus
enteric interneurons establish ___ patterns by inhibiting effector neurons in altering ___
segmentation, segments
interneurons control complex reflex pattern such as…
peristalsis and rhythmic segmentation
what is ileus?
hypomotility or amotility of GI tract in absence of obstruction
what 3 categories of mechanisms are causes of the pathophysiology of post-op ileus?
neurogenic, inflammatory, pharmacologic
what are the pharmacological causes of post-op ileus?
opioid peptides administered exogenously DECREASE transit in GI tract through u2 receptors in myenteric plexus, causing hypomotility
what do opioid peptides do in GI normally?
modulate motility througb receptors on myenteric and submucosal ganglia
inhibits enteric neuron function
what is the enteric NS modulated by?
autonomic NS
the main function of parasympathetic N on enteric system is…
promote digestion
motility patterns, net fluid secretion, vasodilation, enteroendocrine cell degranulation
the main function of sympathetic N on enteric system is…
inhibit digestion and recover fluid volume
stop motility, increase net fluid absorption, vasoconstriction
what is the dominant extrinsic neural tone on GI tract?
parasympathetic
which animals are able to have the ENS operate WITHOUT CNS input?
monogastric animals
what type of innervation is done by vagus nerve?
parasympathetic
what GI does vagus nerve N?
abdominal viscera and pharyngeal mucosa
___ increases gut blood flow, motility, and glandular secretions
ACh
what type of N does splanchnic nerve supply?
sympathetic
splanchnic afferents carry info about…
distension of gut wall, noxious chemicals, inflammation
splanchnic efferents tend to be ___ in nature
inhibitory
____ decreases motility and glandular secretions
norepinephrine
are GI endocrine cells concentrated into glands?
NO
list the main GI hormones
gastrin
CCK
secretin
GIP
motilin
somatostatin
gastrin is released by what type of cells, and where?
G cells
in pyloric antrum and duodenum
gastrin release stimuli
food anticipation, stomach distension, protein/peptides in stomach
gastrin inhibition is done via…
HCl, somatostatin, secretin, GIP
gastrin 4 main functions
- stim K/H ATPase in parietal cells
- stim release of histamines from enterochromaffin-like cells to stim cAMP mediated insertion of K/H ATPase pumps into apical membrane of parietal cells
- gastric motility
- pancreas acinar cells
how are K/H ATPase pumps added to the apical membrane of parietal cells?
gastrin causes release of histamine -> stim cAMP -> pump insertion
somatostatin is released by what type of cell, and from where?
D cells - stomach
delta cells - endocrine pancreas
hypothalamus
somatostatin release stimuli
very low pH in antrum
CCK
somatostatin function
direct and indirect inhibition of gastric acid secretion
explain the direct inhibition of gastric acid secretion done by somatostatin
inhibits adenylyl cyclase of parietal cells, which antagonizes stim effects on histamine
explain the indirect inhibition of gastric acid secretion done by somatostatin
inhibit G cells, ECL cells, parietal cells
how is somatostatin release blocked during the cephalic and gastric phase?
vagal stim
how is somatostatin stimulated for release during the intestinal phase and between meals?
low pH in stomach and CCK
which cells does somatostatin inhibit?
G cells
ECL cells
secretin is released by which cell, where?
S cells in duodenum
secretin release stimuli
fat and acid entry into duodenum
secretin 2 functions
- pH regulation - promotes pancreatic and biliary bicarb secretion as well as bicarb release in duodenum epithelium cells
- reduce gastric acid secretion - block G cells
CCK is released by what cell, where?
I cells
duodenal and jejunal mucosa
neurons in ileum and colon
CCK release stimuli
fa/aa/peptide presence in chyme entering duodenum
CCK inhibition
somatostatin
CCK functions
- enzyme secretion from pancreas
- gallbladder contract to release bile
- activate D cells for somatostatin release
GIP is released from which cell, where?
K cells
duodenal and jejunal mucosa
GIP release stimuli
gls and fa in chyme entering duodenum
glc injected into blood ___ followed by increased GIP activity
IS NOT
injection of glc into SI results in ___ efficient disposal of glc
more
GIP functions
inhibit parietal secretion
increase insulin release from endocrine pancreas
motilin is released by which cell, where?
M cells
duodenal and jejunal mucosa
motilin release stimuli
increasing pH in duodenum
spontaneous release into circulation during interdigestive phase
motilin functions
increase gastric emptying
increase somatostatin release from pancreas
erythromycin is a motilin receptor ___
agonsit
erythromycin function
enhances gastric emptying and intradigestive migratory motor complex
erythromycin side effects
D, abdomen pain, V
the endocrine system helps coordinate functions of the ___ and ___
stomach and SI
how do endocrine control systems affect salivary glands during cephalic phase?
parasympathetic stim of acinar and duct cells
how do endocrine control systems affect gastric secretions during cephalic phase?
parasympathetic stim
ENS (Ach) stim G cells and parietal cells
G cells release gastrin into blood
gastrin finds receptors on parietal and chief cells
how do endocrine control systems affect pancreatic secretions during cephalic phase?
ENS/ACh stim acinar and duct cells
how do endocrine control systems affect salivary glands during gastric phase?
parasympathetic stim
how do endocrine control systems affect gastric secretions/motility during gastric phase?
stomach is distended, so stretch receptors are stim
G cells (gastrin) stim and parietal cells are stim (more H+ into apical membrane)
elevate gastrin levels, since HCl secreted
*low pH will be perceived by G cells to cause inhibition when pH<2
histamine is also produced, stim HCl production and gastrin
how do endocrine control systems affect pancreatic secretions during gastric phase?
ENS stim acinar and duct cells
gastrin acts on CCK receptors
after meal ingestion, the process of ___ starts
gastric emptying
arrival of nutrients into the duodenum triggers ___ feedback on emptying and ___ secretion of digestive enzymes
negative feedback
stim secretions
how do endocrine control systems affect salivary glands during intestinal phase?
cease activity
how do endocrine control systems affect gastric secretion/motility during intestinal phase?
duodenal distension and fat/protein in duodenum trigger CCK secretion, causing stomach to relax
CCK also stim D cells to release somatostatin
how do endocrine control systems affect pancreatic secretions during intestinal phase?
ENS/ACh stim acinar AND duct cells
CCK/secretin stim acinar and duct cells
during the intestinal phase, gastric secretions ___ due to neural and humoral control
decrease
how does neural control inhibit gastric secretions during intestinal phase?
removes stimuli from stomach (pH and stretch)
how does humoral control inhibit gastric secretions during intestinal phase?
somatostatin synthesized/released from D cells
D cells activated by gastrin and CCK
SOMATOSTATIN INHIBITS PARIETAL AND ECL CELL ACTIVITY
how does endocrine control system affect secretions into GI tract during the interdigestive phase (stomach and SI empty)?
NO distension stimulus
reduced gastrin release
somatostatin inhibits gastric and pancreatic secretions, CCK release
motilin stim contraction of gut smooth muscle and interdigestive motility complex, mass movements
what is gastrinoma?
rare neuroendocrine tumor
malignant transformation of somatostatin-secretind delta cells of endocrine pancreas into gastrin-producing cells
what effect does gastrinoma have?
gastrin stim secretion of gastric acid
hypergastrinemia
hypergastrinemia due to gastrinoma can lead to…
esophageal/gastroduodenal ulcers
enzymatic digestion in SI hampered due to increased acid delivery
antral hypertrophy delays gastric emptying
indigestion can cause weight loss/anorexia
D due to maldigestion
treatment options for gastinoma
block H/K pump to improve stomach and duodenum conditions (heal ulcers)
somatostatin use to suppress gastrin secretions
surgery to remove tumor
