lecture 24 - GI motility Flashcards
What are the factors that receptors in the wall of the GI tract respond to?
Stretch (via food in the lumen), change in composition - pH, osmolarity, amino acids, sugars, fats
What are the effectors of GI regulation?
Smooth muscle (contraction), glands (secretion)
What are the 2 types of GI regulation?
Hormonal and nervous (ENS and CNS)
What is the role of the parasympathetic nervous system in GI function?
Stimulates motility and secretion
What is the role of the sympathetic nervous system in GI function?
inhibits motility and secretion
How are the CNS and ENS connected?
The CNS modulates activity of enteric nervous system
What nervous system coordinates GI fucntion over long distances?
Central Nervous System
What component of the ENS regulates secretion?
Submucosal plexus
What component of the ENS regulates motility?
Myenteric plexus
What are the functional differences between the submucosal plexus and myenteric plexus?
Submucosal plexus regulates secretion, while the myenteric plexus regulates motility
What are the 2 key local motility reflexes of the GI system?
Peristalsis and segmentation
What are the 2 key functions of the CNS in GI function?
Integration of responses to external stimuli (senses, emotions, etc.) and response to internal stimuli, such as GI lumen contents via a long reflex path
What neurotransmitter is involved in sympathetic CNS control of the GI tract?
Noradrenaline
What neurotransmitter is involved in parasympathetic CNS control of the GI tract?
acetylcholine
What are the key types receptors that feedback to the ENS?
Stretch/mechano-, osmo- and chemo- receptors
What is the difference between reflex pathways in the ENS and CNS?
Short, local pathways in ENS, long pathways to CNS
What is the largest endocrine organ in the body?
The GI tract
What are the 2 types of hormonal regulation in the GI system?
Endocrine and paracrine
What is endocrine regulation?
Regulation by hormones that are secreted into the bloodstream for distant effect
What is paracrine regulation?
Secretion of hormones to effector cells that are adjacent to the secretory cells
What are the 4 critical hormones of GI regulation?
Gastrin, Gastric Inhibitory Peptide (GIP), Secretin, Cholecystokinin (CCK)
What does the GIP hormone stand for?
Gastric Inhibitory Peptide
What does the CCK hormone stand for?
Cholecystokinin
What are the 2 types of contractions in GI motility?
Tonic and phasic contractions
What are tonic GI contractions?
Sustained contractions for minutes to hours
What feature of the GI system often employ tonic contractions?
Sphincters - they are sustained shut/open for a long time
What are GI phasic contractions?
Waves of contraction and relaxation over seconds
What type of contraction is in peristalsis?
Phasic contractions
What is a motility pattern in the GI tract?
Any pattern of contraction or relaxation of GI tract smooth muscle
What is an example of relaxation being a GI motility pattern?
Storage in the stomach
What are movement/propulsion in terms of motility patterns?
Motility patterns that specifically move or propel GI contents along the tract.
What does it mean when the Gi tract is ‘spontaneously active’?
It contracts without external input
What is the frequency of contraction a property of?
The region of the tract
What is the frequency of contractions in the stomach?
3 per minute
What is the frequency of contractions in the duodenum?
12 per minute
What is the frequency of contractions in the ileum?
9 per minute