Autonomics of the gut

Question 1

What fibers can be found in an autonomic plexus?

Answer 1

Pre and post synaptic sympathetic fibers, pre-synaptic parasympathetic fibers, and afferent fibers.

Question 2

Where are the post-synaptic parasympathetic fibers?

Answer 2

In the walls of the target organ.

Question 3

What is the general effect of parasympathetic action?

Answer 3

Stimulate glandular secretion and peristalsis, as well as cause relaxation of sphincters.

Question 4

What is the general effect of sympathetic action?

Answer 4

Constrict sphincters, increases vasomotor tone, and decrease glandular secretion.

Question 5

What do afferents (GVA) that travel with parasympathetics convey?

Answer 5

Hunger, nausea, stretch/distension, and contribute to visceral reflexes.

Question 6

What do afferents (GVA) that travel with sympathetics convey?

Answer 6

Acute pain from the viscera.

Question 7

Where are the abdominal autonomic plexuses located?

Answer 7

They course on the surface of the aorta and its branches.

Question 8

What do abdominal autonomic plexuses contain?

Answer 8

preganglionic fibers from splanchnic nerves and post-ganglionic sympathetic fibers which originate in pre-vertebral ganglia. Also pre-ganglionic parasympathetic fibers.

Question 9

What ANS plexus innervates the foregut?

Answer 9

The celiac plexus. Distributes via the celiac trunk artery.

Question 10

What ANS plexus innervates the midgut?

Answer 10

The superior mesenteric plexus. Distributes via branches of the SMA.

Question 11

What ANS plexus innervates the hindgut?

Answer 11

The inferior mesenteric plexus. Distributes via branches of the IMA.

Question 12

What nerve provides parasympathetic fibers to the foregut and midgut?

Answer 12

The Vagus nerve.

Question 13

Where are pre-ganglionic cells bodies of the Vagus located?

Answer 13

In the brainstem (dorsal motor nucleus).

Question 14

Where does the Vagus nerve enter the abdomen?

Answer 14

At the esophageal hiatus (T10).

Question 15

What provides parasympathetic fibers to the hindgut?

Answer 15

Pelvic splanchnic nerves.

Question 16

Where are the pre-ganglionic cell bodies of the pelvic splanchnic nerves located?

Answer 16

In the IML horns of S2-S4 spinal cord.

Question 17

How do pre-ganglionic fibers of pelvic splanchnic nerves travel from the spinal cord?

Answer 17

They travel with ventral rami of S2-S4 spinal nerves and then exit the nerve as pelvic splanchnic nerves in the pelvis.

Question 18

Where are the pre-ganglion cell bodies of sympathetics to the abdominal viscera located?

Answer 18

In the T5-L2 spinal cord.

Question 19

How do the pre-ganglionic sympathetic fibers exit the spinal cord?

Answer 19

They enter the sympathetic chain and then exit as splanchnic nerves which enter the aortic plexuses.

Question 20

Do pre-ganglion sympathtetics synapse in the sympathetic chain?

Answer 20

No. They only travel through without synapsing (what makes them splanchnic nerves). Boards will try and trick you on this.

Question 21

What happens after pre-ganglionic sympathetics enter aortic plexuses?

Answer 21

They synapse with post-ganglionic neurons in various pre-vertebral ganglia. These post-ganglionic fibers then distribute via aortic plexuses.

Question 22

What splanchnic nerve provides sympathetic innervation to the foregut?

Answer 22

The greater splanchnic nerve.

Question 23

What splanchnic nerves provide sympathetic innervation to the midgut?

Answer 23

The greater, lesser, and least splanchnic nerves. (also to the kidney in the case of the lesser and least)

Question 24

What splanchnic nerve provides sympathetic innervation to the hindgut?

Answer 24

The lumbar splanchnic nerves.

Question 25

Where are the cell bodies for the greater splanchnic nerve located?

Answer 25

T5-T9

Question 26

Where is the site of synapse for the greater splanchnic nerve?

Answer 26

The celiac ganglion (although some fibers are in the superior mesenteric ganglion).

Question 27

Where are the cell bodies for the lesser splanchnic nerve located?

Answer 27

T10-T11

Question 28

What is the site of synapse for the lesser splanchnic nerve?

Answer 28

The superior mesenteric and aorticorenal ganglia.

Question 29

Where are the cell bodies for the least splanchnic nerve located?

Answer 29

T12.

Question 30

What is the site of synapse for the lesser splanchnic nerve?

Answer 30

The superior mesenteric and aorticorenal ganglia.

Question 31

Where are the cell bodies for the lumbar splanchnic nerve located?

Answer 31

L1-L2.

Question 32

What is the site of synapse for the lumbar splanchnic nerve?

Answer 32

The inferior mesenteric ganglion.

Question 33

What plexus does the abdominal hindgut receive lumbar splanchnic innervation from?

Answer 33

The inferior mesenteric plexus.

Question 34

What plexus does the pelvic hindgut receive lumbar splanchnic innervation from?

Answer 34

The inferior hypogastric plexus (same that distributes pelvic splanchnic nerves).

Question 35

What is the overall location of pre-ganglionic cell bodies for sympathetics to the midgut located?

Answer 35

T8-T12

Question 36

What foregut structures can have referred pain to the shoulder?

Answer 36

The lover and gallbladder receive some innervation from the phrenic nerve. As such there can be referred pain to the shoulder.