Innervation Flashcards
Where are the lower preganglionic sympathetic neurons?
In the intermediolateral cell column between T1 and L2
Route of preganglionic sympathetic neuron leaving spinal cord
Ventral root => spinal nerve (ventral ramus) => white ramus => sympathetic chain ganglion
How does the postganglionic sympathetic neuron return to the spinal nerve from the sympathetic chain ganglion?
Gray ramus
How do GVE sympathetic fibers reach the head and lower parts of the body?
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.
Cervical ganglia
Superior, middle, and inferior
Splanchnic nerve- spinal levels and destination
T1-T4; Travel to heart via the coronary plexus to the cardiac plexus (deep and superficial), sending some fibers also to the pulmonary plexus
Parasympathetic innervation to the heart
Vagus nerves via superior and inferior cardiac nerves
Explain referred pain to the arm due to heart attack
Splanchic nerve to heart originates at T1-T4. T2 gives intercostobrachial nerve
Greater splanchnic nerve level(s)
T5-T9 (varies by source)
Lesser splanchnic nerve level(s)
T10-T11 (varies by source)
Least splanchnic nerve level(s)
T12 (varies by source)
How do the greater, lesser, and least splanchnic nerves reach the abdomen
Enter from the thorax behind crura of diaphragm
Do the thoracic splanchnic nerves synapse in the sympathetic chain ganglia?
Yes
Do the abdominal splanchnic nerves synapse in the sympathetic chain ganglia?
No (but they do pass through. Therefore, they are PREganglionic fibers)
Where does the greater splanchnic nerve synapse?
Celiac ganglion
Where does the lesser splanchnic nerve synapse?
Super mesenteric ganglion
Where does the least splanchnic nerve synapse?
Aorticorenal ganglion
Cranial nerves with parasympathetic outflow
III, VII, IX, X
Sacral parasympathetic levels
S2-S4 (pelvic splanchnic nerves)
Innervation of the hindgut
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
The anterior vagal trunk is derived from which vagus nerve?
Left vagus nerve
The right vagus nerve becomes which vagal trunk?
Posterior vagal trunk
Where to preganglionic parasympathetic neurons synapse?
Intramural ganglia
Direct extension of aortic plexus at the bifurcation
Superior hypogastric plexus
Nerves forming from the superior hypogastric plexus at the level of the sacral promontory
Right and left hypogastric nerves
Components of the inferior hypogastric plexus
Pelvic splanchnic nerves (parasympathetic), hypogastric nerves, and sacral splanchnic nerves (PRE and POSTganglionic sympathetic fibers)
Selective vagotomy
Sectioning of gastric branches of anterior and posterior vagal trunks to reduce gastrin secretion in cases of refractory gastric/duodenal ulcers
The myenteric plexus is normally formed from what embryonic structure?
Neural crest
Cranial neural crest-derived structures
Pharygeal arches/pouches
Neural crest derivatives
MOTEL PASS:
Melanocytes Odontoblasts Tracheal cartilage Enterochromaffin cells Laryngeal cartilage
Parafollicular cells / Pseudounipolar cells
All ganglia / Adrenal Medulla
Schwann cells
Spiral Membrane
Where does the lumbar splanchnic nerve synapse?
Inferior mesenteric ganglion synapse
Sympathectomy
No effect on gut. Used to promote GI vasodilation (extreme hypertension) and pain relief (GVA fibers travel along sympathetic pathways).
What route do GVA fibers take to carry pain information from abdominal organs?
Same route as sympathetics (e.g. splanchnic nerves)
System for somatic pain
Anterolateral system
Anterolateral system route
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.
Lumbar splanchnic nerve spinal level(s)
L1-L2
Celiac plexus block
Used for pain relief (referred). Complications include hypotension (loss of sympathetics), diarrhea (increased parasympathetic influence), and various types of hemorrhages
Explain the pelvic pain line
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.
