Innervation of Abdominal Viscera

Question 1

What is goal of visceral innervation?

Answer 1

1. 3. Convey sensory regulate bloodflow to viscera

2. Control gut movement and secretions (pain and monitoring physiological status)

Question 2

In parasympathetic nervous system, where it the preganglionic cell body located?

Answer 2

Brainstem (vagus nerve); Sacral Spinal Cord segments S2-S4 (via pelvic splanchnic nerve)

Question 3

In parasympathetic nervous system, where is the post ganglionic cell body located?

Answer 3

At terminal ganglia IN organ wall.

Question 4

In sympathetic nervous system, where it the postganglionic cell body located?

Answer 4

Lateral horn of spinal cord segments T5-L2 ONLY

Question 5

In sympathetic nervous system, where is the postganglionic cell body located?

Answer 5

Prevertebral ganglia (located in front of aorta). Note that we are using this INSTEAD of the paravertebral ganglia, but they are the same thing.

Question 6

Which spinal nerve gets the head? The upper limbs? The thorax?

Answer 6

1. T1 = head
2. T2-T4 = thorax
3. C5-T1 = upper limb

Question 7

What is the goal of the enteric nervous system located in the gut wall? What is job of myenteric (auerbauch’s plexus)? If Submucosal (meissener’s) plexus?

Answer 7

1. INTRINSICALLY regulates gi.
2. Cells located between outter longitudinal and inner circular muscle layers. Regulates peristalsis. Aka smooth muscle contraction.
3. Cells located in submucosal layer (deeper to circular muscle fibers). Regulates secretomotor function.

Question 8

Where do the vessels that stimulate, extrinsically, the gi system live? Where do parasympathetics synapse? What about the sympathetics?

Answer 8

1. Inside mesentery layer (not in peritoneal cavity.) Parasympathetics run through this and synapse on myenteric plexus to extrinsically tigger peristolsis. Note that postsynaptics are already in the wall of the gi. Short nerve.
   Note: Sympathetics running through the mesentery wall are ALREADY postsynaptic.

Question 9

Explain enteric extrinsic regulation of myenteric (auerbach’s) plexus

Answer 9

Myenteric:

1. Sympathetic: muscle tone and vascular tone
2. Parasympathetic: Modulate gut wall motility, increase peristalsis

Question 10

Explain enteric extrinsic regulation of Submucosal (Meissner’s) plexus

Answer 10

Submucosal:

1. Sympathetic: Modulate fluid transport
2. Parasympathetic: Secretomotor

Question 11

Describe peristalsis

Answer 11

Outter layer of smooth muscle contracts in front of bolus. Inner layer contracts behind it. When the inner circular layer contract, the outer longitudinal layer is relaxed. Nonmotile motion is occurring to facilitate mixing.

Question 12

Describe Hirschsprung’s Disease (Aganglionic Megacolon). How do you surgically fix this?

Answer 12

Ganglion cells (whicg all migrate from neural crest) never get to wall of intestine….usuallly specifically for sigmoidal-rectal ssegment. RET gene mutation. Result: aganglionic (myenteric plexus) bowel segment becomes constricted and the proximal segments are dilated (hence megacolon). The aganlionization increases extrinsic parasympath and sympath innervation. Symaptheitc ns DOMINATES, increases the smooth muscle tone in segment without ganglion cells. Still note that parasympaths are the ones that synapse in the wall of the colon. So, parasympath has no ganglion to synapse on. Sympaths synapse in vertebral ganglion are still there, and they lead to constriction. Peristolsis is still gonna occur in proximal, ganglion segment, but it can’t get through the constricted part in sigmoid-rectal colon segment (too constricted.). Repair by pulling colon through anus and cutting off the aganglioninc segment. Need to preserve innervation to anus, otherwise you will not be able to control stool removal.

Question 13

What is the purpose of splanchnic nerves? Where do you find postsynaptics sympathetic ganglions?

Answer 13

Connects paravertebral ganglia to prevertebral/preaortic ganglion…note that it is medially directed and that splanchnic nerve is preganglionic. This is where you find postsynaptic sympathetic ganglia. Note that presynaptic is still in lateral horn. Post synaptsics literally follow the arteries after this.

Question 14

Foregut Sympathetics
Prevertebral ganglion:
Splanchnic nerves:
Preganglionic Cell body loctaion:

Answer 14

Foregut Sympathetics
Prevertebral ganglion: celiac
Splanchnic nerves: Greater thoracic splanchnics
Preganglionic Cell body loctaion: T5-T9

Question 15

Midgut Sympathetics
Prevertebral ganglion:
Splanchnic nerves:
Preganglionic Cell body loctaion:

Answer 15

Midgut Sympathetics
Prevertebral ganglion: Superior mesenteric
Splanchnic nerves: lesser thoracic splanchnics
Preganglionic Cell body loctaion: T10-T11

Question 16

Midgut Sympathetics
Prevertebral ganglion:
Splanchnic nerves:
Preganglionic Cell body loctaion:

Answer 16

Midgut Sympathetics
Prevertebral ganglion: Aorticorenal/superior mesenteric
Splanchnic nerves: Least thoracic splanchnics
Preganglionic Cell body loctaion: T12

Question 17

Hindgut Sympathetics
Prevertebral ganglion:
Splanchnic nerves:
Preganglionic Cell body loctaion:

Answer 17

Hindgut Sympathetics
Prevertebral ganglion: Inferior mesenteric
Splanchnic nerves: Lumbar splanchnics
Preganglionic Cell body loctaion: L1-L2

Question 18

Where do the greater, lesser, and least splanchnic nerves run through?

Answer 18

The diaphragm.

Question 19

Describe pathway of innervating a foregut organ (use stomach)

Answer 19

1. Pregranglionic fibers in greater splanchnic nerves…came from T5 to T9. From there, the nerves run and synapse on postganglionic neurons in celiac ganglia.
   The post ganglionic fibers from the celiac ganglia are distributed on branches of celiac trunk to organ wall/pleux.

Question 20

Note about referred pain:

Answer 20

Referred pain comes from the nerve levels associated with the fore, mid, and hindgut.

Question 21

Which kinds of afferents are simply reflexes?

Answer 21

Simpathetic and parasympathetics.

Question 22

What is the order of abdominal pain type from least to most pain, in correspondence to increased stimulant.

Answer 22

Visceral (not a lot of nerve fibers are stimulated)–> referred (lateralized gut) –> parietal (skin, and a lot of nerve fibers are stimulated)

Question 23

Visceral pain:

Answer 23

caused by a random noxious stimulus to abdominal organ (too much acid, obstruction, etc), which irritates free nerve endings.. Pain is dull and poorly localized. Pereived pain = MIDLINE (reason: afferents coming from both left and right.)

Question 24

Referred pain:

Answer 24

result of increased inflammation, stimulation, etc. The organ starts sending off stronger stimulations. More signal to one side of the vertebral column than the other, making the pain more lateralized.

Question 25

Parietal plane:

Answer 25

Legit stimulate the parietal peritoneum. the most intense and precisely localized. Aggravated by movements and coughing. Hurts patient more when the rebounds hits back.