Innervation

Question 1

Where are the lower preganglionic sympathetic neurons?

Answer 1

In the intermediolateral cell column between T1 and L2

Question 2

Route of preganglionic sympathetic neuron leaving spinal cord

Answer 2

Ventral root => spinal nerve (ventral ramus) => white ramus => sympathetic chain ganglion

Question 3

How does the postganglionic sympathetic neuron return to the spinal nerve from the sympathetic chain ganglion?

Answer 3

Gray ramus

Question 4

How do GVE sympathetic fibers reach the head and lower parts of the body?

Answer 4

Preganglionic axons ascend to the cervical extension or descend to the sacral extension and synapse at a different vertebral level. The postganglionic neuron then takes the gray ramus to the spinal nerve.

Question 5

Cervical ganglia

Answer 5

Superior, middle, and inferior

Question 6

Splanchnic nerve- spinal levels and destination

Answer 6

T1-T4; Travel to heart via the coronary plexus to the cardiac plexus (deep and superficial), sending some fibers also to the pulmonary plexus

Question 7

Parasympathetic innervation to the heart

Answer 7

Vagus nerves via superior and inferior cardiac nerves

Question 8

Explain referred pain to the arm due to heart attack

Answer 8

Splanchic nerve to heart originates at T1-T4. T2 gives intercostobrachial nerve

Question 9

Greater splanchnic nerve level(s)

Answer 9

T5-T9 (varies by source)

Question 10

Lesser splanchnic nerve level(s)

Answer 10

T10-T11 (varies by source)

Question 11

Least splanchnic nerve level(s)

Answer 11

T12 (varies by source)

Question 12

How do the greater, lesser, and least splanchnic nerves reach the abdomen

Answer 12

Enter from the thorax behind crura of diaphragm

Question 13

Do the thoracic splanchnic nerves synapse in the sympathetic chain ganglia?

Answer 13

Yes

Question 14

Do the abdominal splanchnic nerves synapse in the sympathetic chain ganglia?

Answer 14

No (but they do pass through. Therefore, they are PREganglionic fibers)

Question 15

Where does the greater splanchnic nerve synapse?

Answer 15

Celiac ganglion

Question 16

Where does the lesser splanchnic nerve synapse?

Answer 16

Super mesenteric ganglion

Question 17

Where does the least splanchnic nerve synapse?

Answer 17

Aorticorenal ganglion

Question 18

Cranial nerves with parasympathetic outflow

Answer 18

III, VII, IX, X

Question 19

Sacral parasympathetic levels

Answer 19

S2-S4 (pelvic splanchnic nerves)

Question 20

Innervation of the hindgut

Answer 20

Pelvic splanchnic nerve fibers (S2-S4) leave the inferior hypogastric plexus to travel up sigmoid mesocolon to innervate the colon distal to the splenic flexure

Question 21

The anterior vagal trunk is derived from which vagus nerve?

Answer 21

Left vagus nerve

Question 22

The right vagus nerve becomes which vagal trunk?

Answer 22

Posterior vagal trunk

Question 23

Where to preganglionic parasympathetic neurons synapse?

Answer 23

Intramural ganglia

Question 24

Direct extension of aortic plexus at the bifurcation

Answer 24

Superior hypogastric plexus

Question 25

Nerves forming from the superior hypogastric plexus at the level of the sacral promontory

Answer 25

Right and left hypogastric nerves

Question 26

Components of the inferior hypogastric plexus

Answer 26

Pelvic splanchnic nerves (parasympathetic), hypogastric nerves, and sacral splanchnic nerves (PRE and POSTganglionic sympathetic fibers)

Question 27

Selective vagotomy

Answer 27

Sectioning of gastric branches of anterior and posterior vagal trunks to reduce gastrin secretion in cases of refractory gastric/duodenal ulcers

Question 28

The myenteric plexus is normally formed from what embryonic structure?

Answer 28

Neural crest

Question 29

Cranial neural crest-derived structures

Answer 29

Pharygeal arches/pouches

Question 30

Neural crest derivatives

Answer 30

MOTEL PASS:

Melanocytes
Odontoblasts
Tracheal cartilage
Enterochromaffin cells
Laryngeal cartilage

Parafollicular cells / Pseudounipolar cells
All ganglia / Adrenal Medulla
Schwann cells
Spiral Membrane

Question 31

Where does the lumbar splanchnic nerve synapse?

Answer 31

Inferior mesenteric ganglion synapse

Question 32

Sympathectomy

Answer 32

No effect on gut. Used to promote GI vasodilation (extreme hypertension) and pain relief (GVA fibers travel along sympathetic pathways).

Question 33

What route do GVA fibers take to carry pain information from abdominal organs?

Answer 33

Same route as sympathetics (e.g. splanchnic nerves)

Question 34

System for somatic pain

Answer 34

Anterolateral system

Question 35

Anterolateral system route

Answer 35

Pain information comes into dorsal horn and synapses. Lamina I and V fibers cross over immediately to contralateral side and go up to the thalamus.

Question 36

Lumbar splanchnic nerve spinal level(s)

Answer 36

L1-L2

Question 37

Celiac plexus block

Answer 37

Used for pain relief (referred). Complications include hypotension (loss of sympathetics), diarrhea (increased parasympathetic influence), and various types of hemorrhages

Question 38

Explain the pelvic pain line

Answer 38

Pelvic structures covered by peritoneum are “above the pelvic pain line” (e.g. roof of bladder and uterus), and GVA fibers travel with sympathetic fibers to T11-L2 spinal levels. Below the pelvic pain line, GVA fibers travel with pelvic splanchnic nerves to S2-S4.