Ward: Gastric physio of digestion (cont'd) Flashcards
Regulation of gastric secretion occurs via two main ways
- neural pathway
2. hormonal pathway
The neural pathway of gastric stimulation relies on (blank) nerve stimulation
vagal
The hormonal pathway of gastric stimulation relies on these two hormonal effectors
histamine
gastrin
(blank) stimulates secretion of a wide range of substances including pepsinogen, HCl, mucus, and gastrin
ACh
(blank) and (blank) strongly stimulate the release of HCl by parietal cells.
gastrin; histamine
The first phase of gastric secretion. Occurs before food enters the stomach. Stimulated by the senses. Stimulus originates in the cerebral cortex or amygdala/hypothalamus and reaches the stomach via the vagus.
Cephalic phase
What portion of gastric secretion is associated with the cephalic phase
20-30%
The second phase of gastric secretion. Gastric distension and partially digested proteins stimulate mechano-receptors which stimulate paretial cells through short local enteric reflexes and long vagovagal reflexes
Gastric phase
What portion of gastric secretion is associated with the gastric phase?
60%
The presence of proteins in the duodenum can cause the release of small amounts of gastric juices possibly through release of gastrin. Distension of the intestine also causes acid secretion possibly through the release of enterooxyntin, a hormone from endocrine cells. Several inhibitory factors released by the intestine can override the minor excitatory effects of gastrin
Intestinal phase
What portion of gastric secretion is associated with the intestinal phase?
10%
Things that can result in a decrease in secretion from the enteric nervous system and vagal nerves
distension
acid in upper intestine
protein breakdown products
irritation of the mucosa
Intestinal hormones released as a result of acid, fat protein breakdown products, hyper-hypo osmotic fluids
secretin
CCK
somatostatin
When the pH of the stomach decreases below 3, the endocrine cells in the antrum secrete (blank) that inhibits the release of gastrin and gastric secretion
somatostatin
In the antrum, what stimulus inhibits gastrin release and acid secretion? What mediator inhibits gastrin release and acid secretion?
acidsomatostatin
In the duodenum, what stimulus inhibits gastrin release and acid secretion? What mediators inhibit gastrin release and acid secretion?
acid
secretin
nervous reflex
In the duodenum and jejunum, what stimulus inhibits gastrin release and acid secretion? What mediator inhibits gastrin and acid secretion?
fatty acids
GIP
What cell types secrete pepsinogen? Is it active or inactive when secreted? How is it activated?
mucous, chief cell
inactive
comes in contact with HCl to become activated
proteolytic enzyme active at low pH (~2)
pepsin
ACh causes an influx of (blank) into the oxyntic cell, resulting in acid secretion.
Ca+
Gastrin binding to its receptor also causes influx of (blank)
Ca+
Histamine does not require extracellular Ca+ for stimulation of acid secretion. What is the intracellular messenger that couples histamine to H+ secretion?
cAMP
What causes the release of gastrin from pyloric glands? Gastrin is carried in the blood stream and stimulates the release of (blank) and (blank).
vagal and local stimulation; histamine and HCl
glycoprotein secreted by parietal cells: It is essential for the absorption of vitamin B12 in the ileum. Failure to secrete this can lead to this condition.
Intrinsic factor; pernicious anemia
