Digestive System 3 Flashcards
What are the 3 phases of secretion in the stomach ?
- Cephalic
- Gastric
- Intestinal
What is the cause of the cephalic phase ?
Sensations and thoughts
What is the effect of the cephalic phase ?
Cerebral cortex/ hypothalamus
Parasympathetic- vagus
What do enteroendorcine cells in the small intestine release ?
- Cholecystokinin (CCK)
- Gastric inhibitory peptide (GIP)
- Secretin
They inhibit gastric secretion.
What effect do CCK and secretin have on the pancreas?
CCK stimulates secretion of pancreatic juice rich in bicarbonate ions
Secretin stimulates secretion of pancreatic juice rich in digestive enzymes
What effect do CCK and secretin have on the liver ?
CCK causes contraction of the gallbladder.
Secretin enhances flow of bile rich in bicarbonate ions from the liver
What are satiety signals ?
They make you feel like you don’t want to eat anymore. You are full.
What is CCK ?
It is secreted in response to food.
Reduces appetite and inhibits eating
Name 5 satiety signals
- Glucagon-like peptide-1, from intestine
- Peptide YY, from intestine
- Leptin, from white adipose tissue
- Insulin
- Oestrogen
What is ghrelin ?
A hormone that increases food intake, it is a hunger signal
Where is ghrelin secreted from ?
Endocrine cells of gastric mucosa
What is the melanocortin system?
A set of neurones that respond to melanocyte-stimulating hormones.
It integrates long and short term signals.
Activates by POMC/CART
Inhibited by NPY/AgRP
What surpresses NPY and AgRP neurons?
Insulin and Leptin
What does NPY do ?
Activates its receptor which is a GPCR.
Stimulates eating
What do AgRP do ?
Bind to and inhibit MC4R.
Inhibits anorexiegenic effects of alpha-MSH.
What stimulates POMC/CART neurons ?
Leptin
When is gastrin secreted?
When PH rises.
It is inhibited when PH is less than 2
What does gastrin do?
- Stimulates gastric secretions
- Contraction of cardiac sphincter
- Increased motility
- Relaxes pyloric sphincter
What stimulates parietal cells to release HCl?
- Gastrin
- Acetylcholine
- Histamine
