LEC 1 (Regulatory Substances in the GIT) Flashcards
GI hormone classification
- depending on structure
2. depending on function t
GI endocrine (hormones)
released from endocrine cells in the GI mucosa ►portal circulation, ►general circulation ►physiologic actions on target cell
D Cell
somatostatin
G Cell
Gastrin
H Cell
VIP
S Cell
Secretin
I Cell
chole-cysto-kinin(CCK)
K Cell
gastric inhibitory peptide (GIP).
G Cell location
in the lateral walls of gastric glands in the antral portion of the gastric mucosa
Gastrin found in
stomach, pituitary gland, hypothalamus, medulla oblongata, vagus and sciatic nerve.
Gastrin contains
17 amino acids (“little gastrin”)
Gastrin form
- Little gastrin
2. Big gastrin
Little Gastrin is secreted in
response to a meal
Gastrin all biologic activity resides in the
four C-terminal amino acids.
G17 have half-life of
2 to 3 minutes in the circulation,
G34 has a half-life of
15 min
Actions of gastrin
↑ gastric acid and pepsin secretion
↑growth of mucosa of the stomach, and small and large intestines (trophic action
↑gastric motility.
↑insulin secretion
trophic action
gastrin ↑growth of mucosa of the stomach, and small and large intestines
Patients with gastrin secreting tumors
hypertrophy (size of cells) and hyperplasia (number of cells) of the gastric mucosa.
insulin secretion ؟
only after a protein meal, and not carbohydrate meal
Stimuli for secretion of gastrin
- Luminal
- Neural
- Blood borne
Luminal stimuli
- Stimuli for secretion of gastrin
- Distention of the stomach.
- Small peptides and amino acids,
Zollinger-Ellison syndrome (gastrinoma)
gastrin is secreted by non-β-cell tumors of the pancreas
Neural stimuli
Vagal stimulation, mediated by gastrin-releasing peptide (GRP)
.Stimuli for secretion of gastrin
(GRP)
is not acetylcholine (Ach).→Atropine DOSE NOT block vagally mediated gastrin secretion
Blood borne stimuli for secretion of gastrin
Calcium (hypercalcemia),
Epinephrine
Inhibition of gastrin secretion
Luminal
2.Blood borne
Inhibition of gastrin secretion Blood borne
Secretin, somatostatin, GIP (Gastric inhibitory polypeptide also known as the glucosedependent insulin-tropic peptide), VIP (vasoactive intestinal peptide), glucagon
Inhibition of gastrin secretion Luminal
↑acid →direct action on G cells
→release of somatostatin.
→ no gastrin
acid located
in the antrum
pernicious anemia
acid-secreting cells of the stomach are damaged, gastrin secretion
is chronically elevated
CCK half-life of circulating
5 minute
CCK is secreted from
I cells in duodenum and jejunum
The biologic activity of CCK resides in the
C-terminal heptapeptide (7).
CCK location
In the brain, especially the cerebral cortex
CCK function
regulation of food intake
the production of anxiety and analgesia
CCK structure
33 amino acids
CCK form
CCK58, CCK33, CCK22 and
CCK8
2.Big gast
small gastrin.