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Gut to brain and brain to gut (Satiety and Appetite (Vagal afferent…
Gut to brain and brain to gut
CNS and ENS
CNS
Connected to ENS via VAGUS and SPLANCHNIC nervous pathway
ENS
Set of Neurones in stomach and gut
Myenteric and submucosal plexus: sheets
Brain-gut axis
Afferent
Gut to brain
spinal afferent
Efferent
Brain to gut
Sympathetic efferent
Autonomic neurons
Vagal (paraysymphathic) efferents
Via enteric neurons
Enteric: control motility, secretion, blood flow and mucosal growth
Sympathetic efferents
Act on blood vessels and enteric neurons
Interdigestive period:
Ghrelin
Gastric distenison
: (mechanoreceptors)
Intestinal nutrients
: (hormone, paracrine mediators)
Decrease food intake via vagal afferents
Vagal efferents
Decrease gastric emptying
Increase pancreatic secretion
Gastric secretion
Gut immune responses
Phases:
Cephallic
: release of Ach and gastrin releasing peptide
Gastric
: release of gastrin
Intestinal
: release of inhibitory factors
Gut derived pain
:
Splanchnic afferent neurons
Cell bodies in DRG: project into GI tract muscle layers and mucosa
Satiety and Appetite
Satiation:
Prompts the termination of eating: amount consumed one sitting
Satiety
: Fullness that persists after eating : Length of time until next eating
Vagal afferent neurons
Enteroendocrine cells EECs
E.g. CCK
Respond to luminal nutrients
Largest endocrine organ in body
CCK receptor:
Nodose ganglion
Express receptors for many gut hormones
Receptors transported from cell soma to peripheral
Vagal afferent neurons
Gut hormones
GLP-1
Regulator of nutrient utilization, integrator of brain and gut function
Inhibits
Food intake
Gastric emptying
(Via vagal afferent neurons)
(Delays nutrient delivery to small intestine)
Stimulates
Insulin secretion
Ghrelin
Stimulator of nutrient intake, integrator of brain and gut function
Stimulates
Food intake and gastric emptying
Receptors
Expressed on vagal afferent and hypothalamic neurons
Secretion
Highest in blood after meal
Inhibits
Actions of CCK on vagal afferent neurons
CCK
Regulator of small intestine digestion:
integrator of brain and gut function
Stimulates:
Pancreatic
enzyme secretion
Gall bladder contraction
(promoting small intestine digestion)
Inhibits
Food intake
Gastric emptying
(Via vagal afferent neurons)
(Delays nutrient delivery to small intestine)