Regulation of gut function Flashcards
What is the intrinsic nervous system for the gut called?
Enteric nervous system.
What does activation of the sympathetic nervous system do to the gastrointestinal tract?
Inhibits gastrointestinal tract activity.
Sympathetic nerves emerging from what ganglion innervate the stomach?
Coeliac ganglion.
Sympathetic nerves emerging from what ganglion innervate the small intestine?
Superior mesenteric ganglion.
Sympathetic nerves emerging from what ganglion innervate the colon?
Inferior mesenteric and pelvic ganglion.
What neurotransmitter acts on the gut from the sympathetic nervous system?
Noradrenaline.
What neurotransmitter acts on the gut from the parasympathetic nervous system?
Acetylcholine.
What parasympathetic nerves innervates the stomach, small intestine and proximal colon?
Vagus nerve.
What are the two types of muscle that makes up the muscularis? What plexus is between these muscle layers?
Circular muscle and longitudinal muscle. Myenteric plexus.
What is the nerve plexus in the submucosa called?
Submucosal plexus/Meissner’s plexus
What is the myenteric plexus responsible for?
Controls gut motility.
What is the submucosal plexus responsible for?
Senses the gut lumen environment. Controls secretion, blow flow, epithelial and endocrine cell function.
What stimulates sensory neurones in myenteric plexus?
Distention of gut.
What stimulates sensory neurones in submucosal plexus?
Chemicals in food.
What is peristalsis?
Sequential contraction and relaxation of circular and longitudinal muscle to propel food along GI tract.
What muscles cause propel food in peristalsis?
Contraction of circular muscles before bolus.
What muscles are responsible for receiving the bolus in peristalsis?
Contraction of longitudinal muscles widen the lumen to receive bolus.
Examples of what parasympathetic nervous system does to the GI tract?
Increase peristalsis, increase absorption, increase secretions.
What does the enteric nervous system to the extrinsic autonomic nervous system?
Modulates sympathetic and parasympathetic nervous system via sensory neurones to the brain.
What is hirschsprung’s disease? What does it result in?
Congenital absence of ganglion of myenteric and submucosal. Enlarged colon.
What are neurocrine hormones? What secretes them?
Hormones that affect nerves. Postganglionic non-cholinergic neurones of the enteric nervous sytem.
Where are hormone containing granules in enteroendocrine cells?
Basolateral membrane.
How does enteroendocrine cell release of endocrine hormones happen
Food molecules, distention or vagus nerve stimulate enteroendocrine cells to release endocrine hormones via the basolateral membrane into the capillaries.
What are some hormones release from the stomach?
Gastrin and ghrelin.
What are some hormones released from the duodenum?
Secretin and CCK.
What kind of hormones are released from the duodenum and stomach?
Secretory hormones.
What kind of hormones are released from the distal small intestine and large bowel?
Inhibitory hormones.
What part of the stomach is gastrin secreted from?
Antrum.
What stimulates release of gastrin?
Amino acids and peptides present in the lumen of the stomach. Gastric distention and vagus nerve.
What does gastrin do?
Stimulates gastric acid secretion by parietal cells. Trophic (growth) effects on mucosa layer.
When is gastrin secretion inhibited?
When pH of stomach falls below 3.
What would you seen in a gastrinoma?
Ulcer (too much acid) and hypertrophy of stomach wall.
What cells secrete secretin?
S cells.
What is the main stimulus for secretin secretion?
Presence of acid in the duodenum.
What does secretin do?
Pancreatic and biliary bicarbonate secretion. Inhibits gastrin. Inhibition of gastric emptying. Trophic effect on the exocrine pancreas.
What stimulates release of CCK?
Fat and peptides in upper small intestine.
What does CCK do?
Stimulates pancreatic enzyme release. Stimulates gallbladder contraction and relaxation of sphincter of oddi. Delays gastric emptying and decreases food intake.
What hormones have trophic effects on the pancreas?
Secretin and CCK.
What is another name for gastric inhibitory peptide?
Glucose-dependent insulinotropic peptide.
What stimulates release of GIP?
All 3 macronutrients.
What cells secretes GIP and where are these cells located?
K cells in duodenum and jejunum.
What does GIP do?
Stimulates insulin secretion.
What does motilin do?
Increase gastrointestinal motility.
What is the universal inhibitor (inhibits most gut hormones) hormone in the gut?
Somatostatin.
What cells secrete somatostatin?
Delta cells.
What does somatostatin do in relation to the gut?
Inhibits gastric secretion, motility, secretions and release of gut hormones.
What cells release GLP-1 and where is it released?
L cells and small intestine.
What stimulates release of GLP-1?
Hexose and fat.
What does GLP-1 do?
Increases sensitivity of pancreatic beta cells to glucose. Induce satiety.
What does pancreatic polypeptide do?
Induce satiety.
What stimulates pancreatic polypeptide release?
Fat
What does peptide YY do?
Reduce intestinal motility, gallbladder contraction and pancreatic exocrine secretion.
What cells release peptide YY? When is it released?
L cells after digestion.
What are some neurocrine gut hormones?
Vasoactive intestinal peptide, gastrin release peptide and enkephalins.
What does vasoactive intestinal peptide do?
Relaxation of gut smooth muscle.
What does gastrin releasing peptide do?
Induces gastrin release.
What do enkephalins do?
Increase smooth muscle tone.
What is zollinger ellison syndrome?
Where you develop gastrinomas.
How to treat zollinger ellison syndrome?
Parietal cell proton pump inhibitor and somatostatin analogues.
What hormones are released in the intestinal phase?
Secretin, gastric inhibitory polypeptide, CCK.
What does the enterogastric reflex act on to inhibit gastric motility?
Myenteric plexus.
What occurs in the intestinal phase?
Chemoreceptors detect acid chyme. Enterogastric reflex. Inhibition of parasympathetic nervous system. Release of secretin, gastric inhibitory polypeptide, CCK.
