1-GI tract Flashcards
what are the 4 major functions of the GI system?
digstion
absorption
excretion
host defense
how is blood supplied to the system? what is unusual about the blood circulatory pathway?
portal circulation, all the blood from the digestive tract empties directly into the liver
what is the role of the autonomic system in regulation of GI physiology?
not 100% necessary
motility and secretion (sight/smell/emotions)
what is enteric nervous system
intrinsic regulation
contained completely within the walls of the GIT
what is intrinsic innervation
enteric regulation
contained completely within the walls of the GIT
what is extrinsic innervation
autonomic nervous system
not 100% necessary
influences motility and secretion of gut (sight/smell/emotions)
what is the role of hormones in regulation of the GI processes
they participate in a feedback control system that regulate some aspect of the GI system
what is neurocrine
what do you call the substance
chemical messenger released from nerve travels across synapse and acts upon a post-synaptic synapse
neurotransmitter!!!!!
what is endocrine
what do you call the substance
chemical messenger from cell released to blood into (distant) target
hormone!!!!!!!!!
what is paracrine
chemical messenger diffuses through intestinal fluid to nearby cells
what is autocrine
chemical messenger acts on the same cell that produced it
what kinds of muscle activity occur in the GI tract
peristalsis and segmentation
what is basic electrical rhythm
pacemaker cells that undergo spontaneous depolarization/repolarization
what does the serosa do and what is it made of
connective tissue
encases intestine, forms connection point to abdominal wall
what does the myenteric plexus do
influences smooth muscle (inbetween the circular and longitudinal muscle)
submucosal plexus what do
influences secretion (between muscle, lymph and blood)
what is peristalsis/ which muscle contracts and relaxes
circular contracts & longitudinal relax on oral side
longitudinal contracts & circular relax on anal side
how does segmentation work
contraction and relaxation of intestinal sements with little net movement of contents towards large intestine
where is most segmentation occuring
small intestine
where are slow waves propagated
circular and longitudinal muscle
how are slow waves depolarized more significantly
neural or hormonal input to bring it closer to threshold
what kind of cells release gastrin
g cells
where are g cells
stomach antrum
what do g cells release
gastrin
what stimulates gastrin release
peptides in stomach, parasym. nerves
what does gastrin cause
more HCl and motility
what cells secrete secretin
s cells
what do s cells secrete
secretin
what causes secretin release
acid in small intestine
what does secretin release cause
less HCl, less motility
increased HCO3- and H2O from pancreas abd bile
what cells release GIP
k cells
where are k cells
small intestine
where are s cells
small intestint
what causes GIP release
glucose or fat in small intestine
what does GIP release cause
raise insulin
what cells release CCK
I cells
where are I cells
small intestine
what causes CCK release
digested fat/ protein in small intestine
what happens when CCK is relased
lower HCl and motility
more pancreatic enzymes and bile released
what are long reflexes
come from brain, go to gut
what are short reflexes
receptors through nerve plexus to effector cells within the GI tract
what is exocrine
chemical messenger secreted into ducts then onto epithelial surface ( no blood )
does the enteric system depend on the CNS
no, independent of CNS
what is in the enteric system
myenteric plexus & submucosal plexus
does the intrinsic system depend on the CNS
no, independent of CNS
what is in the intrinsic system
myenteric plexus & submucosal plexus
