Introduction to the ENS Flashcards
What are the two major plexus in the Gi tract?
Submucosal plexus found between submucosa and the circular muscle
Myenteric plexus found between the circular and the longitudinal muscle
Both are extensively interconnected
Where is the submucosal plexus found?
Stomach and intestines only
Where is the myenteric plexus found?
The whole length of the Gi tract
What is the function of the ENS?
Regulates digestion
blood flow to Gi tract
secretions in Gi tract
+ many more
What are the components of the neurones in the enteric NS
Why is this significant?
Sensory receptors
mechanoreceptors (detect stretch)
chaemoreceptors
Interneurones
Excitatory and inhibitory that coordinate input and output
Efferent (secretomotor) neurones
Inhibitory and Excitatory !!
Many different neurotransmitters used
Effectors:
smooth muscle or glands
All the components for a short enteric reflex are present
What is the motor reflex?
Where and how does it occur?
Motor reflex is essentially peristalsis
occurs in the myenteric plexus
Bolus simulates mechanoreceptors and cheamoreceptors
sensory input to myenteric plexus
Directly stimulate excitatory efferents or through excitatory interneurones also excite excitatory efferents
this results in contraction behind the bolus (head end)
Also directly excite inhibitory efferents or indirectly through excitatory interneurones(activating inhibitory efferents) or inhibitory interneurones inhibiting excitatory motor efferents
results in relaxation in front of bolus (Anus end)
What is the secretory reflex and where does it occur?
In the submucosal plexus
Bolus sensory afferents direct inputs into the submucosal plexus
Signals through interneurones then into excitatory or inhibitory efferents that lead to increased or decreased enzyme secretion
What plexus does monitoring blood flow to the Gi tract involve?
Both the myenteric and submucosal plexus
What is Chagas disease?
Specific ENS disease
trypanosome parasite produces a toxin that causes neurone death
What is Hischsprung’s disease?
Specific ENS disease
Congenital absence of ENS neurones usually confined to distal colon manifesting soon after birth
Distal colon unable to carry out peristalsis and thus faeces builds up
Abolition of rectoanal reflex leading to abnormal defication
Treatment is surgery colostomy to remove colon with no neurones in it
What is significant about the ENS
Is linked to the CNS via long reflexes allowing CNS to override the ENs in certain situations
How is the ENS related to parkisons disease?
General neurological condition not ENS specific but there is a strong link between the gut health and onset of Parkinsons
