Gut motility Flashcards
What is the role of the upper oesophageal sphincter?
Controls entry of food bolus into GI tract (initiated by the process of swallowing)
What is the role of the External anal sphincter?
allow defecation
what are the 2 main areas of innervation of GI tract?
o Myenteric plexus – most important
o Submucosal plexus
Role of the Interstitial cells of Cajal?
These are cells located within the muscle layers of the alimentary tract.
They mediate communication between the autonomic nervous system and smooth muscle
When is the enteric nervous system active?
all the time
what are the extrinsic factors that influence the enteric nervous system?
what effect do they each have on non-sphincteric muscle ?
o Parasympathetic (Vagal) – excitatory to non-sphincteric muscle o Sympathetic – inhibitory to non-sphincteric muscle, excitatory to sphincteric muscle
What are the neurohormonal influences on the enteric nervous system?
o 5 hydroxy tryptamine (serotonin)
o Motilin
o Opioid receptors
what does interprandial mean?
between meals
Describe the difference between the muscular layers found in the 1/3 of the oesophagus versus the lower 2/3
upper 1/3: striated voluntary muscle
Lower 2/3: smooth muscle, circular and longitudinal layers (involuntary)
When does the migrating motor complex occur and what is its role?
occurs in interprandial period (between meals)
It is a cyclic contraction sequence which cleanses stomach and intestine of any remaining food in between meals
How often does the migrating motor complex occur? what is it regulated by ?
Every 90 minutes
Regulated by Motlin
Describe the 4 stages of the migrating motor complex
1) prolonged period of quiescence
2) increased frequency of contractility
3) a few minutes of peak electrical and mechanical activity
4) declining activity merging to next phase 1
What is motilin and what is it produced by?
A Polypeptide hormone
Produced by M cells in the small intestine
How often is motilin secreted and what effect does it have?
Secreted every 90 minutes
It stimulates contraction of gastric fundus and enhances gastric emptying
Name a motilin agonist and what is a common side effect of it?
Erythromycin: common side effect = diarrhoea as there is too much cleansing of the gut
