L14 Flashcards
The major long term energy storage pool is ___________
triglycerides in adipose tissue.
orexigenic vs anorexigenic systems
orexigenic - increase energy intake and decrease energy expenditure
anorexigenic - decrease energy intake and increase energy expenditure
5 things that happen when you have a positive energy balance
- Adipose mass increases
- Secretion of insulin and leptin increases
- Insulin and leptin activate anorexigenic system and inhibit orexigenic system
- Decreases food intake and increases energy expenditure
- Decreases energy storage
compare the 2 networks of the enteric nervous system
myenteric plexus - exerts control primarily over digestive tract motility
submucous plexus - sensing the
environment within the lumen, regulating GI blood flow and controlling epithelial cell function
12 hormones secreted by GI tract
1) Secretin
2) Gastrin
3) cholecystokinin (CCK)
4) gastric inhibitory peptide (GIP)
5) vasoactive intestinal peptide (VIP)
6) substance P (SP)
7) somatostatin (SOM)
8) gastrin releasing peptide
9) bombesin
10) neurotensin
11) motilin
12) Ghrelin
true or false: GI hormones meet the criteria of “true” hormones
false; they are not secreted from specific endocrine glands, and their actions at target cells have not been elucidated
gastrin function and stimuli for release
prescence of peptides/AAs in gastric lumen –> gastrin –> stimulates gastric acid secretion and proliferation of gastric epithelium
cholecystokinin function and stimuli for release
fatty acids and AAs in small intestine –> cholecystokinin –> secretion of pancreatic enzymes, contraction/emptying of gallbladder
secretin function and stimuli for release
acidic pH in lumen of small intestine –> secretin –> secretion of water and bicarbonate from pancreas and bile ducts
ghrelin function
strong stimulant for appetite/feeding
also a potent GH stimulator
motilin function and stimuli for release
associated with fasting
stimulates housekeeping patterns of motility in stomach/SI
gastric inhibitory peptide function and stimuli for release
prescence of fat/glucose in SI –> GIP –> inhibits gastric secretion and motility and potentiates release of insulin from beta cells
3 phases of digestion
- cephalic
- gastric
- intestinal
describe the cephalic phase of digestion
- salivary secretion by parasympathetic NS due to sight, smell, taste –> enzyme-rich saliva
- stimulates Ach
- 30% of gastric acid secretion
gastric acid is released from _____ cells
parietal
describe gastric phase of digestion
- stomach distension –> stretch receptors –> release of Ach by VAGOVAGAL REFLEXES –> gastric acid secretion
- proteins –> peptides/AAs –> gastrin secretion
50% of acid secretion from this phase
4 important cell types in gastric mucosa
- parietal cells –> release HCl
- enterochromaffin-like cell –> secretes histamine which stimulates HCl secretion
- D cells secrete somatostatin which inhibits HCl secretion
- G cells release gastrin which stimulates HCl secretion
what stimulates D cells? what’s the result?
acid in the stomach (low pH) –> somatostatin release –> inhibition of gastric acid secretion
syndrome associated with excess gastrin
Zollinger Ellison Syndrome
3 negative feedback signals of gastric acid secretion
- somatostatin
- CCK
- secretin
what kind of receptor pathway do acetylcholine and gastrin use to stimulate acid release?
Gq - IP3/Ca2+
what kind of receptor pathway does histamine use to stimulate acid release?
Gs — cAMP
true or false: NPY stimulates food intake
true
Central administration of ghrelin increases hypothalamic expression of _____
NPY
describe what happens to macromolecules in the absorptive state
carbohydrates –> blood glucose for ATP synthesis, excess = glycogen/fat
fats –> chylomicrons, primary energy for liver/fat/muscle cells
amino acids –> many cells, in liver it may be used for protein/ATP/FA synthesis
explain the first component of intestinal phase of digestion
excitatory:
very short, stretch receptors –> gastrin, chemoreceptors detect FA and glucose –> gastrin
explain the inhibitory component of the intestinal digestion phase
enterogastric reflex - inhibit vagovagal/myenteric reflex, inhibit gastric secretion
enterogastrone secretion:
enteroendocrine cells release CCK, GIP, secretin, VIP –> inhibit gastric secretion
what cells in the small intestine produce CCK?
I-cells
