Gastrointestinal Flashcards
Where do parasympathetic nerves to the GI tract have their first extracranial synapse? What are the neurotransmitters and receptors at this synapse?
In gangion surrounding the gut; Ach on nicotinic Ach receptors
Where do sympathetic fibers to the GI tract first synapse?
In prevertebral ganglion
What is the neurotransmitter at the postganglionic synapse for sympathetic innervation of the gut?
Norepinephrine
Which layer of the GI tract contains the ganglia that hold the first synapses for parasympathetic fibers coming from the brain?
Auerbach’s plexuses in the muscularis externa
Does the enteric nervous system have more or fewer neurons than the spinal cord?
Many more
Which plexuses contain the cell bodies of the enteric nervous system?
Meissner’s plexuses (submucosal)
What effect does nitric oxide have on the GI tract?
Sphincter relaxation
For each of the following, do they act mostly as hormones or neuropeptides in the GI tract?
– Gastrin
– Secretin
– Gastrin-releasing peptide (GRP)
– GIP
– Glucagon, GLP-1, GLP-2
– VIP
– Motilin
– Gastrin: hormone
– Secretin: hormone
– Gastrin-releasing peptide (GRP): neuropeptide
– GIP: hormone
– Glucagon, GLP-1, GLP-2: hormone
– VIP: neuropeptide
– Motilin: hormone
For each of the following, do they act mostly as hormones or neuropeptides in the GI tract?
– Substance P; tachykinins
– Pancreatic polypeptide
– Peptide YY
– Ghrelin
– Substance P; tachykinins: neuropeptides
– Pancreatic polypeptide: hormone
– Peptide YY: hormone
– Ghrelin: hormone
Are G-cells in the proximal or distal part of the stomach?
Distal
What receptor does gastrin bind to?
CCK receptor-B
How is gastrin release inhibited? What cells release this modulator?
By somatostatin released from D cells
What three regulators will stimulate acid production by the parietal cell?
Gastrin, histamine, and Ach
What does the prefix cholecysto- refer to?
Gall bladder
Cholecystokinin stimulates contaction of what organ, and secretion of what enzymes?
Gallbladder contraction; pancreatic enyme secretion
Both secretin and CCK induce secretion of what ion?
Bicarbonate: HCO3-
Both secretin and somatostatin inhibit release of what hormone that acts on the stomach?
Gastrin
What are the major actions of vasoactive intestinal peptide (VIP)?
Epithelial cell secretion and smooth muscle relaxation (in the sphincter of Oddi)
What are the three effects of the tachykinin Gastrin Releasing Peptide (GRP)?
Mediates of the vagal release of gastrin, stimulates pancreatic secretion, and increases GI motility
What antibiotic is an agonist for motilin? What side effect does this cause?
Erythromycin; overactive gut
Where is ghrelin made? What is its principle effect?
In the fundus of the stomach; it increases food intake
What stimulates the release of somatostatin? What inhibits its release?
Gastric acid in the lumen; inhibited by high luminal pH
What are ECL cells in the gut? What do they release to promote gastric acid release?
They are a type of neuroendocrine cell found in the gastric glands of the gastric mucosa beneath the epithelium in the vicinity of parietal cells. They release histamine in response to gastrin.
Saliva contains what major ion? What is its principal function in the distal esophagus?
Bicarbonate; neutralizes gastric acid to protect distal esophagus