Neural & Hormonal Control of Gastrointestinal Function 2 Flashcards
What causes relaxation of the pylorus?
activity of enteric neurons
What is the protease present in the stomach?
pepsin
Why is the food ground up in the stomach?
So it is available to digestive enzymes in the duodenum
Why is there slow release of stomach contents into the duodenum?
Because the duodenum can only deal with the acid in small amounts
What is the last nutrient to reach the duodenum?
Fat
What are the three things that activate neural feedback?
acid, distension and nutrients (mostly amino acids)
What thing in the duodenum inhibits gastric emptying?
acid - via the vasovagal reflex
What does acid in the duodenum activate?
D cells to release somatostatin
What is the action of somatostatin released in the duodenum?
excites terminals of vagal afferents to trigger vasovagal reflex that causes Brunner’s glands to release mucus and bicarbonate
What do amino acids and fatty acids activate in the duodenum?
CCK release from I cells
What is the action of CCK?
excites vagal neurons to regulate appeptite and enteric neurons to set up motor activity in the intestine
What else do amino acids activate in the duodenum?
The release of secretin from S cells
What is the action of secretin?
Causes secretion of bicarbonate from the pancreas
What is the action of bicarbonate?
neutralises gastric acid to inactivate pepsin and to stop somatostatin secretion and also to re allow gastric emptying - also allows enzymes in the duodenum to work
How does the pancreatic secretions access the duodenum above the pancreatic duct?
Via retropulsion
What is the action of CCK as a hormone?
release of digestive enzymes from the pancreas, acts on hypothalamus to partly suppress appetite, gall bladder contraction
How does the mucosa get sensory information?
Via mechanical stimulation activating mechanoreceptors and nutrients stimulating EE and EC cells
What is the action of taste receptors in the lumen of the GIT?
cause release of serotonin from EC cells
What are L cells?
cells which express the components of sweet taste receptors and release glucagon like peptide 1 and 2 and pancreatic polypeptide Y to regulate appetite and insulin secretion
What is the action of olfactory receptors on EC cells?
release of serotonin from the EC cells
What are the motor patterns activated in the duodenum?
segmentation, peristaslsis and retropulsion
What modulates proportion of segmentation and peristalsis?
nutrients activating EE and EC cells
What determines efficacy of digestion and absorption?
rate of transit
What are the short chain fatty acids produced by fermentation?
acetate, butyrate, propionate
What triggers urge to defacate?
distension of rectum
What happens in irritable bowel syndrome?
the threshold is reduced and can sense content that is not normally detectable
How is the anal sphincter relaxed?
with conscious neural activity
What is the migrating motor complex?
A wave of contraction in the fasting state to clear bacteria and cellular debris
What is ghrelin?
a growth hormone release inhibitor - released from the stomach in the fasted state - stimulates appetite
What is gastrin releasing peptide?
a hormone in nerve terminals near G cells that acts in parallel with vagally release acetylcholine
