Lecture 8: Innervation of the Gastrointestinal Tract

Question 1

Major control of the GI system is the ….

Answer 1

ANS (via smooth muscle and glandular tissue regulation)

Question 2

Features of the ANS

Answer 2

Hypothalamic control

Paraganglionic (CNS) to Postganglionic (target organ)

Question 3

What SNS nerves work on the GI system?

What is their main function?

Answer 3

Splanchnic Ns. (T5-L2) from lataeral horn

Abdominal visceral response to stress

Question 4

What PNS nerves work on the GI system?

What is their main function?

Answer 4

CN X
Pelvic Splanchnic Ns. (S2-S4)
homeostasis

Question 5

Greater Splanchnic N. (SNS)
Origin?
Synapses where?

Answer 5

T5 - T9

Celiac ganglion around the celiac trunk

Question 6

Greater Splanchnic N. innervates which organs sympathetically?

Answer 6

all other organs not mentioned (most major GI organs)

Question 7

Lesser Splanchnic N (SNS)
Origin?
Synapses where?

Answer 7

T10 - T11

Superior Mesenteric ganglion around the SMA

Question 8

Lesser Splanchnic N. innervates which organs?

Answer 8

-Jejunum, ilieum
Cecum
Ascending and transverse colon

Question 9

Least Splanchnic N. (SNS)
Origin?
Synapses where?

Answer 9

T12
Aorticorenal ganglion (around renal arteries)

Question 10

Least Splanchnic N. innervates which organs?

Answer 10

Kidneys
Adrenal medulla

*by leeching off the renal arteries

Question 11

1st and 2nd Lumbar Splanchnic Ns. (SNS)
Origin?
Synapses where?

Answer 11

L1-L2
Intermesenteric plexus (anterior artery between SMA and IMA)

Question 12

1st/2nd lumbar splanchnic ns. innervate which organs?

Answer 12

Descending, sigmoid colon
proximal rectum

*leech off the IMA

Question 13

3rd/4th Lumbar Splanchnic Ns. (SNS)
Origin?
Synapses where?

Answer 13

3rd: L3
4th: L4-L5

Inferior hypogastric plexus by distal aorta/anterior sacrum (mostly) and Superior hypogastric plexus by ureter (some)

Question 14

3rd/4th Lumbar Splanchnic Ns. innervate which organs?

Answer 14

Pelvis and perineal organs

*leech off branches of the internal iliac a.

Question 15

Sacral Splanchnic Ns. (SNS)
Origin?
Synapse where?

Answer 15

S1-S5
Inferior hypogastric plexus

*leech off the internal iliac branches to get to pelvic/perineal organs

Question 16

Vagus N. (PNS)

Origin?

Answer 16

-Dorsal motor nucleus of vagus

Question 17

Vagus N. parasympathetically supplies which organs?

Answer 17

Anterior vagal divison: stomach via enteric plexus

Posterior vagal division: 
pancreas
liver
biliary system
small intestine
proximal large intestine

Question 18

Pelvic Splanchnic Ns. (PNS)

Origin?

Answer 18

S2-S4

Question 19

Pelvic Splanchnic Ns. parasympathetically supplies which organs?

Answer 19

Descending and sigmoid colon
Rectum
Anal canal
Urogenital organs and perineum

Question 20

What causes somatic abdominal pain?

What are its characteristics?

Answer 20

• parietal peritoneal irritation as diseased organ rubs against the peritoneum, sending pain info to brain via somatic afferents (T7-12)
• acute (severe) localized pain, sensitive to rebound tenderness (stretching of parietal peritoneum)

Question 21

What causes visceral pain?

What are its characteristics?

Answer 21

• diseased organ transmits pain info to splanchnic nerves to spinal cord
• poor localization (dull to severe), radiates around a dermatome distribution, brain interpretation is all over the place