Enteric Nervous System (ENS)
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What is the ENS
A subdivision of the ANS that directly controls the GI system
Where is the ENS found?
Embedded in the lining of the GI system
How can the ENS work?
INDEPENDENTLY of the brain + spinal cord
What are the 2 plexuses in the ENS
Submucosal plexus Myenteric plexus
How does the ENS normally communicate w/ the CNS?
Through the parasympathetic + sympathetic NS
When the ENS is communicating with the CNS how is it doing it through the parasympathetic NS
Via the vagus nerve
When the ENS is communicating with the CNS how is it doing it through the Sympathetic NS
Via the prevertebral ganglia
What type of neurones does the ENS have?
Efferent Afferent Interneurones
What do all the neurones make capable in the ENS?
Make it capable of carrying reflexes + act as an integrating centre in the absence of CNS input.
Where is the myenteric plexus located?
Between inner + outer layers of the muscularis externa
Where is the submucosal plexus located
In the submucosa
What is the myenteric plexus concerned with?
Motility throughout the whole gut.
How is the myenteric plexus organised?
As a longitudinal chain of neurones.
What happens when the myenteric plexus is stimulated?
⬆️ TONE of gut + velocity + intensity of contractions.
What does inhibition of the myenteric plexus allow?
Relaxation of the sphincters
What is the submucosal plexus concerned with?
Local conditions: • Controls local secretions, absorption + muscle movement
What do the mucosa + epithelial tissues associated with the submucosal plexus have?
Sensory nerve endings = Feed signals to both layers of the enteric plexus. Also send info back to the sympathetic pre-vertebral ganglia, spinal cord + brain stem.
Why is the ENS described as a 2nd brain?
Due to being able to operate autonomously
How many NTs does the ENS make use of?
30+ incl. Acetylcholine Dopamine Serotonin
How much of the bodys serotonin is found in the gut?
90% +
How much of the bodys dopamine is found in the gut?
50%+
Regulation of the ENS
Parasympathetic NS is able to stimulate the enteric nerves to ⬆️ enteric function. Stimulation of the enteric nerves by the sympathetic NS will INHIBIT enteric function.
What do the parasympathetic enteric neurones function in?
Defecation + provide a rich nerve supply to the sigmoid colon, rectum + anus.