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Sympathetic Nervous System, Part 2

Notes

Sympathetic Nervous System, Part 2

Sections


Summary

Postganglionic Fiber Projections

Thoracic projections

  • Upper and lower postganglionic fibers project to the thorax.
    We specifically show the:
  • Lower respiratory tract:
    • Trachea
    • Lungs
  • Heart

Divergence and convergence

Divergence

  • To illustrate divergence, we draw a pair of preganglionic sympathetic fibers that originate from the same preganglionic neuron and synapse on separate postganglionic neurons.

Convergence

  • To illustrate convergence, we draw a pair of preganglionic sympathetic fibers that originate separately and synapse together on a single postganglionic neuron.

Prevertebral ganglia

Celiac ganglion

  • Preganglionic fibers pass the paravertebral chain and synapse on the celiac ganglion, which innervates the:
    • Upper 1/3 of the GI tract: the esophagus to the duodenum (the foregut derivatives).
    • Adominal organs, represented by the liver.
  • Preganglionic fiber synapse on the aorticorenal ganglion, which innervates the:
    • Kidneys
    • Adrenal glands (aka suprarenal glands).
  • Preganglionic fibers synapse on the superior mesenteric ganglion, which innervates the:
    • Middle 1/3 of the GI tract: the small intestine to the proximal 2/3 of the transverse colon (the midgut derivatives).
  • Preganglionic fiber synapse on the inferior mesenteric ganglion, which innervates the:
    • Lower 1/3 of the GI tract: distal 1/3 transverse colon to anal canal (the hindgut derivatives).
    • Lower urinary system – the bladder with lower portion of the ureters.
    • Reproductive organs (represented by the uterus and fallopian tubes).
  • Representative preganglionic sympathetic fiber bypass the paravertebral ganglia and synapse directly in the adrenal gland.
    • The adrenal gland releases epinephrine (predominantly).

The abdominopelvic splanchnic nerves

From superior to inferior:

  • The greater splanchnic nerve innervates the celiac ganglion.
  • The lesser splanchnic nerve innervates the aorticorenal ganglion.
  • The least splanchnic nerve innervates the superior mesenteric ganglion.
  • The lumbar splanchnic nerve innervates the inferior mesenteric ganglion.

sympathetic innervation of the limbs

  • One important clinical correlation is that the stellate ganglion innervates the upper extremity. Stellate sympathectomy is a treatment for upper extremity involvement in reflex sympathetic dystrophy (aka complex regional pain syndrome).

Full-Length Text

  • This is part 2 of the sympathetic nervous system tutorial.
  • Now, show a representative preganglionic sympathetic fiber project from the spinal cord to the paravertebral chain.
  • Then, show upper and lower postganglionic fibers project to the thorax.
  • Specifically, show the:
    • Lower respiratory tract (the trachea and lungs).
    • Heart.

Let's pause for a moment and introduce a common phenomenon in the sympathetic nervous system: divergence and convergence.

  • To illustrate divergence: draw a pair of preganglionic sympathetic fibers that originate from the same preganglionic neuron and synapse on separate postganglionic neurons.
  • Then, to illustrate convergence: show a pair of preganglionic sympathetic fibers that originate separately and synapse together on a single postganglionic neuron.

Now, let's draw the lowermost portion of the sympathetic nervous system.

  • Show a preganglionic fiber pass the paravertebral chain and synapse on the celiac ganglion, which innervates:
    • Upper 1/3 of the GI tract: the esophagus to the duodenum (the foregut derivatives).
    • Adominal organs, represented by the liver.
  • Show a preganglionic fiber synapse on the aorticorenal ganglion, which innervates:
    • The kidneys
    • The adrenal glands (aka suprarenal glands).
  • Show a preganglionic fiber synapse on the superior mesenteric ganglion, which innervates:
    • Middle 1/3 of the GI tract: the small intestine to the proximal 2/3 of the transverse colon (the midgut derivatives).
  • Show a preganglionic fiber synapse on the inferior mesenteric ganglion, which innervates:
    • Lower 1/3 of the GI tract: distal 1/3 transverse colon to anal canal (the hindgut derivatives).
    • Lower urinary system – the bladder with lower portion of the ureters.
    • Reproductive organs (represented by the uterus and fallopian tubes).
  • Next, show a representative preganglionic sympathetic fiber bypass the paravertebral ganglia and synapse directly in the adrenal gland.
  • Indicate that it releases epinephrine (predominantly).
  • Now, list the abdominopelvic splanchnic nerves, from superior to inferior:
    • The greater splanchnic nerve innervates the celiac ganglion.
    • The lesser splanchnic nerve innervates the aorticorenal ganglion.
    • The least splanchnic nerve innervates the superior mesenteric ganglion.
    • The lumbar splanchnic nerve innervates the inferior mesenteric ganglion.
  • Finally, in regards to sympathetic innervation of the limbs, write that one important clinical correlation is that the stellate ganglion innervates the upper extremity.
    • Stellate sympathectomy is a treatment for upper extremity involvement in reflex sympathetic dystrophy (aka complex regional pain syndrome).