GI2 Flashcards
what are the GI self-regulatory hormones?
- CCK
- secretin
- GIP
- gastrin
- motilin
what are the GI self-regulatory neurocrine secretions?
- Ach
- NO
- Substance P
- VIP
- Serotonin
what are the GI self-regulatory candidate hormones?
- enteroglucagon
- pancreatic polypeptide
- peptide YY
what are the GI self-regulatory paracrine secretions?
- histamine
- somatostatin
- serotonin
a gut hormone must:
- be excreted by a cell in the gut or exert its effect on the gut
- use endocrine route (blood)
- stimulated by food
- not dependent on neural control
where is gastrin produced
G cells; duodenum and pancreas
what is gastrin’s release stimulus?
peptides, AAs
what is gastrin’s major action?
(+) parietal cell HCl secretion
where is secretin produced?
S cells in the duodenum; jejunum
what is secretin’s release stimulus?
acid, fat, protein
what is secretin’s major action?
(+)HCO3- secretion, (-) HCl secretion
where is CCK produced?
I cells; small intestine and enteric neurons
what is CCK’s release stimulus?
fats, proteins
what is CCK’s major action?
(+) pancreatic enzyme and insulin secretion; (+) bile secretion; satiety factor
where is GIP produced?
K cells; duodenum and jejunum
what is GIP’s release stimulus?
fats and glucose
what is GIP’s major action?
(-) gastric secretions; (+) insulin secretion
where is motilin produced?
M cells; duodenum, jejunum
what is motilin’s release stimulus?
increase in duodenal pH; ACh
what is motilin’s major action?
antral and duodenal MMC, Phase III induction during digestion
what cells produce the greatest proportion of serotonin?
enterochromaffin cells
-present all throughout the GI tract
what does serotonin (5-HT) stimulate?
- ENS
- vagal afferents (gut->brain)
- enterocyte secretion
- blood flow
what stimulates enterochromaffin cells?
- hyperosmolality
- acidity
T’F: stimulation of serotonin receptors can cause nausea?
true
what are trophic effects of regulatory peptides?
- supply and demand
- increase feed, increase demand
- increase production and secretion of trophic factors
what does gastric cause the growth of?
gastric mucosa
what two things cause the growth of intestinal mucosa?
- enteroglucagon
- cholecystokinin
what regulatory peptides are increased for cold adaptation? (increased food intake)
- CCK (elongation of intestinal villi)
- enteroglucagon (enhanced absorption)
the greater the propulsive movement, the (higher/lower) the transit time and the (greater/lower) the transit rate.
- lower
- greater
the lower the propulsive movement, the (higher/lower) the transit time and the (greater/lower) the transit rate.
- greater
- lower
what is a syncytium?
a multinucleated mass of protoplasm such as a striated muscle fiber
what faciliates protoplasmic continuity between smooth muscle cells, thereby inparting smooth muscles with the properties of a syncytium?
gap junctions
what are gap junctions?
intercellular channels that permit exchange of substances(eg. Ca2+, cAMP, ATP) between cells)
how many connexons and connexins does each gap junction have?
2 connexons 12 connexins (6/connexon)
what is the basic electrical rhythm of GI smooth muscle?
slow waves
are slow waves always present?
yes
smooth muscle cells are ___ electrically and forma functional ___.
- coupled
- syncitium
what is electrical coupling between cells facilitated by?
gap junctions
are slow waves neurogenic or myogenic?
myogenic
-no neural input is required
what cells serve as the pacemaker cells of the GI tract?
ICC (interstitial cells of Cajal)
how do ICC cells work?
they partially depolarize and set basic electrical rhythm
do smooth muscle slow wave frequency, amplitude and kinetics differ between species?
yes
do smooth muscle slow wave frequency, amplitude and kinetics differ between segments of the GI tract?
yes
