enteric system Flashcards
(18 cards)
what does the enteric system even do?
The ENS gives input from the sympathetic and parasympathetic but it also has a local reflex that allows much of digestion to proceed even without input
where is the enteric nervous system found?
embedded in the lining of the gut
what activity does the enteric system regulate?
regulates the activity of the intestines (peristalsis), local blood flow, and glands
why is the enteric nervous system called the 2nd brain?
enteric nervous system has more neurons than the spinal cord
enteric neurons are in a network built into where
the walls of the GI tract
what is its main goal of the ENS
move food (bolus) from oesophagus to rectume
- peristaltic reflect (this is local and goes without impulse)
steps of the ENS working
- sensory neuron: detects stretch due to the bolus
- interneurons: report to neighbours
- neuron behind the bolus: contract smooth muscle (ACh)
- neuron ahead of bolus: relax smooth muscle (various NTs)
when is seratonin released
(larger change in tone in response to stimulus)
by gut in response to food (stretching)
what does the release of serotonin cause
- causes increased ACh release (contraction behind)
- increased transmitter release ahead of bolus (relaxation)
→ more movement
how the ENS responds to input from the Sympathetic Nervous system = what could be the input?
dopamine: (also can be a change in tone in a larger context)
when is dopamine released
indirectly released in response to sympathetic activity
what effects does the release of dopamine have?
- reduces ACh release (less contraction behind)
- reduces transmitter release ahead (less relaxation)
- a brake on the whole peristaltic circuit: less digestion, also reduces secretions and absorption of nutrients
effect of opioids on the ENS
-> why chronic opioid treatment = constipation
- endogenous opioids activate opioid receptors, and stop ACh signalling in ENS, slowing peristalsis
- reduce ACh release (less contraction behind)
how does the sympathetic NS know to regulate the ENS
our viscera (including sensory neurons in the ENS, transmit sensory information back to the sympathetic ganglia and the CNS)
What are General Visceral Afferent (GVA) fibres classified as?
They are not classified as sympathetic, parasympathetic, or enteric.
What key sensory inputs do GVA fibres detect?
Stretch in the GI tract and blood pressure.
How do GVA fibres innervate the viscera?
They provide diffuse innervation and can run alongside sympathetic nerves, entering the spinal cord one or two vertebrae above/below the expected level.
