gastrointestinal regulation Flashcards
which branchs of the nervous system does GI regulation involve?
the autonomic system (and the enteric nervous system)
why doesn’t the enteric nervous system need to achieve homeostasis?
because the amount of nutrients involved is not determined by internal conditions, but by how we eat
what is the function of the ENS?
to maximise digestion and absorption
what is the ENS consisted of?
the submucosal plexus and the myenteric plexus.
what is the function of the submucosal plexus?
coordinates secretions
what is the function of the myenteric plexus?
coordinates GI tract motility through short and long reflex arcs
outline the difference between a short reflex arc and a long reflex arc
short:
stimulus->GI receptors->nerve plexus->effector organ in GI tract
long:
stimulus->GI receptor->CNS->nerve plexus->effector organ
where are the endocrine cells in the digestive system and what is their function?
they are found in the stomach and the small intestine, they secrete hormones directly into the blood in response to specific stimuli.
which nervous system is this controlled by?
the enteric NS
name four examples of hormones secreted by these endocrine cells and state their site of secretion and function
gastrin, secreted in stomach in response to proteins, stimulates gastric secretion and motility.
CCK, secreted in duodenum and jejenum in response to fats/proteins, stimulates bile secretion.
secretin, secreted in duodenum and jejenum in response to acid, stimulates production of bicarbonate-rich pancreatic juice.
Glucose-independent Insulinotonic peptide, secreted in duojenum and jejenum in response to glucose/fats, stimulates secretion of insulin by the pancreas.
what are the 3 phases of GI regulation and where is the site of stimulation?
cephalic phase- in head
gastric phase- stomach
intestinal phase- small intestine
what occurs during the cephalic phase?
initiated by sight/smell/taste of food. increases gastric juice secretion and stomach motility.
what occurs during the gastric phase?
initiated by arrival of bolus at the stomach. stomach expands which is detected by stretch receptors and the change in protein concentration is detected by chemoreceptors.
ENS short and long reflex arc activated:
peristalsis and gastric secretion
what occurs during the intestinal phase?
initiated by arrival of chyme at the s intestine.
chemoreceptors activated in the duodenum
gastric juice inhibited
reduces stomach motility
fatty acids and glucose stimulate endocrine cells which produce:
GIP
secretin
CKK
