Regulation of GI function Flashcards
Two plexuses of enteric nervous system
Myenteric - increases velocity and intensity of gut contractions
Submucosal - involved with local conditions and controls local secretions, absorption and muscle movement
What is the function of enteric nervous system
Controls motility and secretion of digestive tract
What are the common features between ENS and CNS
Intrinsic neurons - lie completly within the wall of the gut; neuron signals from CNS to GI system
Neurotransmitters and meuromodulators
Glial support cells - Similar to astroglia of the brain
Integrating centre - Allows for relexes that originate in GI tract to be acted on without neural signal leaving ENS; ENS has it’s own integrating centre
What is the submucosal plexus
COntrols local secretion and absorption, and muscle movement
Mucosa and epithelial tissue associatedwith it have sensory nerve endings that feed signals to both layers of enteric plexus
THese tissues also sends info back to spinal sord and brainstem
What is the myenteric plexus
Longituidinal chain of neurons
COntrols velocity anf intnsity of contractions
Inhibition of myeteric system causes relaxation of muscle movement
How do short reflexes occur in ENS
Impulses originate in ENS and are integrated there without outside input
Submucosal plexus contains sensory neurons that receive signals from gut lumen
ENS integrates this information and initiates responses
Submucosal plexuses controls secretion by GI cells; myenteric plexuses in mucularis influence motility
What is feedforward reflexes
Sight, smell, sound and thought of food
What are emotional reflexes
Butterflies in stomach, psychologically induced vomiting
Enteroendocrine cells
G cells S cells ECF Chief cells Parietal cells Beta cells
Digestive hormones
Gastrin - acid secretion
Cholecystokinin - Stimulates secretion of pancreatic enzymes and contraction and emptying of the gall bladder
Secretin - stimulates secretion of water and bicarbonate ions
Somatostatin - inhibits gastrin and histamine secretion
GIP - inhibits gastrin secretion and motility, stimulates insulin release
What is gastrin
Promotes gastric acid release, increases histamine release and gastric motility
Synthesised and secreted from G cells
Bind to receptors found on parietal and ECF cells
What reflexes cause gastrin release
Short reflexes - release stimulated by amino acids and peptides in stomach
Release also triggered in cephalic reflexes - parasympathetic neurons form the vagus nerve stimulate G cells to release gastrin
What is cholecystokinin
Secreted from I cells in SI
Released when fats/proteins present in SI
Stimulates release of pancreatic enzyme and bile
What is secretin
Secreted from S cells in the SI
Inhibits secretion of gastric acid form parietal cells
Stimulates production of bicarbonate solution from ductal cells in the pancreas
What is secretin
Secreted from S cells in the SI
Inhibits secretion of gastric acid form parietal cells
Stimulates production of bicarbonate solution from ductal cells in the pancreas
