regulation of GI function Flashcards
what is the enteric nervous system
short reflex arcs located within wall of GI tract and can operate independently of rest of body
has sensory and motor cells
what do simple reflex arcs consist of
single sensory cell and a single motor nerve cell.
what do complex reflex arcs consist of
single reflex arcs connected by interneurons
what do short reflex arcs enable
enable GI tract to have extensive control of its activities
what is the main transmitter of reflex arcs
acetylcholine
what does the parasympathetic system promote
digestion
where are pre-ganglionic fibres located (parasympathetic)
vagus nerve
where are post ganglionic fibres located (parasympathetic)
embedded in the wall of the GI tract and connect to the enteric nervous system
where are pre-ganglionic fibres located in the sympathetic NS
run in splanchnic nerves
what is the transmitter of pre-ganglionic fibres in SNS
acetylcholine
where are post-ganglionic fibres located in SNS
run along arteries to organ of innervation or in hypogastric nerves
what is the transmitter of post-ganglionic in SNS and function
noradrenaline to inhibit secretion, motility and decrease blood supply to the GI tract
what do entero-enteric reflexes do
co-ordinate activity between different parts of the GI tract
where is the production site of the hormone gastrin
caudal stomach
what is the stimulation of hormone Gastrin
peptides and amino acids
acetylcholine
what effect does the hormone Gastrin have
stimulates HCL, stimulates grown of gastric/intestinal mucosa
production site of secretin
duodenum
what is the stimulation of secretin
HCL
effect of secretin
stimulates pancreatic HCO3-
production site of CCK
duodenum
stimulation of CCK
fatty acids, monoglycerides, amino acids, peptides
effect of CCK
stimulates pancreatic enzymes
contracts gall bladder
production site of Gastric Inhibitory Peptide (GIP)
cranial small intestine
stimulation of GIP
fat, glucose, amino acids
effect of GIP
inhibits HCL
stimulates insulin production
what are the 3 phases of regulation
cephalic phase - head
gastric phase - stomach
intestinal phase - intetines
what is the cephalic phase co-oridinated by
ANS
what is the gastric phase co-ordinated by
ANS, ENS and hormones - gastrin
what is the intestinal phase co-ordinated by
ANS, ENS, and hormones - secretin, CCK and GIP
what is the regulation of appetite controlled by in the brain
hypothalamus
what does the appetite centre do
causes food searching and voracious eating
direct effect on animals behaviour
what does the satiety centre do
causes refusal of food
inhibits appetite centre
what are the 3 theories of mechanism of action
glucostat
cck
lipostat
what is motility
co-ordinated contraction of smooth muscle in the GI tract
what are the 4 types of contraction
segmental
peristalsis
anti-peristalsis
mass movement
what is segmental contraction
mixes lumen contents
mechanical breakdown
what is peristalsis
move intestinal contents in a gradual aboral direction
what is anti-peristalsis
moves intestinal contents in an oral direction eg rumination/vomiting
what is mass movement
empties entire sections of GI tract
eg evacuate colon contents into rectum prior to defaecation
what happens when pacemaker cells reach threshold potential
action potential to cause smooth muscle contraction
what determines strength of contraction
frequency of action potentials
what are action potentials due to
opening of calcium channels
