Nerve Supply Flashcards
What is a splanchnic nerve?
Autonomic nerve, not necessarily containing parasympathetic or sympathetic fibers exclusively, could be mixed
Which plexuses supply the abdominal viscera?
The plexuses around the 3 unpaired visceral arteries, they are periarterial plexuses (nerve fibers reach viscera via blood vessels)
1) Coeliac plexus
2) Sup. mesenteric plexus
3) Inferior mesenteric plexus
Where do parasympathetic fibres originate from?
Brainstem (cranial nerves)
Sacral region of spinal cord - S2, S3, S4 (not S1 or S5)
Where do sympathetic fibres originate from?
Thoracic region of spinal cord - T1-T12
Lumbar region of the spinal cord - L1, L2, L3 (not L4/L5)
From which levels of the spinal cord do the fibres which make up the greater splanchnic nerves originate from?
T6, T7, T8, T9
From which levels of the spinal cord do the fibres which make up the lesser splanchnic nerves originate from?
T10 and T11
From which level of the spinal cord do the fibres which make up the least splanchnic nerves originate from?
T12
From which level of the spinal cord do the fibres which make up the lumbar splanchnic nerve originate from?
L1, L2, L3
What kind of fibres are carried in the greater, lesser, least and lumbar splanchnic nerves?
Sympathetic
What is the parsympathetic and sympathetic supply to the coeliac plexus which supplies the foregut?
Parasympahtetic = Vagus Sympathetic = greater splanchnic
What is the parasympathetic and sympathetic supply to the sup. mesenteric plexus which supplies the midgut?
Parasympathetic = Vagus Sympathetic = lesser and least splanchnic nerves
What is the parasympathetic and sympathetic supply to the inf. mesenteric plexus which supplies the hindgut?
Parasympathetic = pelvic splanchnic (from S2,S3,S4) Sympathetic = Lumbar splanchnic (from L1,L2,L3)
What kind of fibres run in the pelvic splanchnic nerve?
Parasympathetic
What are the 3 things which can happen to a sympathetic fibre as it leaves the spinal cord?
Sympathetic fibres originate from the lateral horn, they follow the course of the somatic efferent fibres until they jump off to travel to the sympathetic chain via the white ramus communicans they can then do 1 of 3 things:
1) Travel straight through without synapsing in the paravertebral ganglia - travel to viscera via splanchnic nerves still as pre ganglionic fibres (this is what happens to the fibres supplying the abdominal viscera!)
2) Synapse at the paravertebral ganglia and post synaptic fibres travel via the grey ramus communicans to join with the somatic nerves to supply the body wall
3) Synapse at the paravertebral ganglia and the post synaptic fibres leave the spinal cord and travel via splanchnic nerves to supply the viscera
Where do the sympathetic fibres supplying the abdominal viscera synapse?
At the prevertebral/preaortic ganglia
1) Coeliac ganglia (Either side of coeliac trunk)
2) Sup. mesenteric ganglia (either side of sup. mesenteric artery)
3) Inf. mesenteric ganglia (either side of inf mesenteric artey)
The post synaptic fibres then form the plexuses around the blood vessles
Where do parasympathetic fibres synapse?
In the gut, in the wall of the target organ, have long pre synaptic and very short post synaptic fibres
Do the coeliac and superior mesenteric plexuses communicate?
Yes
How do the superior mesenteric and inferior mesenteric plexuses communicateʔ
Via the intermesenteric plexus
What is the function of visceral afferent fibres from the gut and which route do they travel byʔ
ɢive CɴS info eg. tell the CɴS the gut is stretched and cause it to release enzymes as it has food in it
Visceral afferent nerves carrying this information travel via the parasympathetic nerves
What is a plexusʔ
Autonomic hub of mixed parasympathetic and sympathetic fibres
What is the superior hypogastric plexus, what is it formed from and where is itʔ
Sits around the bifurcation of the abdominal aorta, direct continuation of the intermesenteric plexus