Enteric nervous system Flashcards
What nervous system is the enteric a part of?
The 3rd division autonomic nervous system
What does intramural plexus mean?
It means the same as enteric nervous system
What is the enteric nervous system?
Intrinsic innervation of the GI tract
What area does the enteric nervous system cover?
Oesophagus to rectum
What size is the network of neurones?
80-100 million
Where is the enteric nervous system?
In two plexuses
Submucosal
Myenteric
Describe the submucosal plexus
Also known as Meissner’s plexus
Stomach and intestine only
Describe the myenteric plexus
Also know as Auerbach’s plexus
Full length of the GIT
Do the submucosal and myenteric plexuses interact?
Yes
Extensively interconnected
List the layers of the small intestine from the lumen moving out
Lumen Mucosa Submucosa Circular muscle Longitudinal muscle
Where do you find the myenteric plexus?
Between the circular muscle and longitudinal muscle
Where will you find the submucosal plexus?
Between the submucosa and circular muscle
What types of neurones are present?
Afferent sensory neurones
Interneurones
Efferent secretomotor neurones
What kind of reflex is this?
A short reflex
What type of sensory neurones are present?
Mechanoreceptors
Chemoreceptors
What do interneurones do?
Coordinate input and output
What types of interneurones are present?
Excitatory and inhibatory
What neurotransmitter do excitatory interneurones use?
Acetylcholine
What neurotransmitter do inhibitory interneurones use?
Many various neurotransmitters
What do efferent neurones do?
Excitatory or inhibitory
They innervate motor and sensory effectors
What are the motor effectors?
Smooth muscle
What neurotransmitter do excitatory efferent neurones use?
Acetylcholine
Substance P
5-HT (seratonin)
What neurotransmitter do inhibitory efferent neurones use?
Nitric oxide
Vasoactive intestinal peptide
Adenosine triphosphate
(more)
What are secretory effectors?
Cells that secrete enzymes
What neurotransmitter do efferent neurones from secretory effectors use?
Excitatory
Acetylcholine
VIP
What three things does the enteric nervous system control?
Motility
Secretion
Blood flow to the gut
What is the motor reflex in the enteric nervous system?
Peristalsis
Which plexus is involved in peristalsis
Myenteric plexus
How does information reach the myenteric plexus?
Afferent sensory neurones run from the lumen to the myenteric plexus
How does the myenteric plexus have an effect?
Efferent neurones innervate the muscle layers
What effect on the GI tract will a bolus have?
Mucosal stimulation (chemoreceptor) Distension (mechanoreceptor)
What happens before and after the bolus?
Contraction behind
Relaxation in front
How does the muscle contract?
Via excitatory interneurones
How does the muscle relax?
Via inhibitory interneurones
Which plexus is responsible for the secretory reflex?
The submucosal plexus
How does sensory information reach the submucosal plexus?
Sensory afferent neurone from the lumen
Where do efferents of the secretory reflex go?
From the submucosal plexus to the lumen
List the chain of events of the secretory reflex
Sensory receptors (mechano and chemo)
ENS (submucosal plexus)
Secretory neurones
Secretion (mucus, enzymes or acid)
How does the enteric nervous system affect blood flow?
Blood flow should increase when digesting food
Decrease when no food being digested
Which plexus is involved in controlling blood flow?
Myenteric plexus
How does the myenteric plexus affect blood flow?
By release of vasoactive neurotransmitters
How does the enteric nervous system integrate with the central nervous system?
Via the sympathetic and parasympathetic pathways to the brain
What kind of reflex is the involvement of the central nervous system?
Long reflex
CNS influence _____ along the GIT. Give an example
varies
We cannot control movement of food in the oesophagus
We can control the anal sphincter
Describe Hirschprung’s disease (megacolon)
Absence of enteric nervous system neurones Distal colon Manifest soon after birth No ejection of faeces Leads to distension and colitis
How do you treat Hirschprung’s disease
Remove (via surgery) the a-ganglionic section of the colon
What is Chaga’s disease?
Trypanosome parasite
Releases toxin that causes neurone death
What is IBS?
Dysfunctional interaction between the central nervous system and enteric nervous system
