The Thoracolumbar Outflow Sympathetic Nervous System

a. Refer to paragraph 11 -10b(2) which describes the H-shaped region of gray matter in the cross section of the spinal cord. Imagine extending the cross link of the H slightly to the left and right of the vertical arms; the extended ends would correspond to the intermediolateral gray columns. Cell bodies of the first neurons of the sympathetic NS make up those columns between the T-1 and L-2 levels of the spinal cord, a total of 14 levels. Here, we are speaking of preganglionic sympathetic neurons.

b. Cell bodies of the second neurons make up various sympathetic ganglia of the body. These ganglia include the trunk or chain ganglia and the pre-aortic or "central" ganglia. Here, we are speaking of post- ganglionic sympathetic neurons.

c. The sympathetic NS innervates:

(1) Peripheral visceral organs (example: sweat glands).

(2) Central visceral organs (examples: lungs and stomach).

d. The neurons innervating the peripheral visceral organs are distributed to them by being included in the nerves of the PNS.

e. The sympathetic NS activates those visceral organs needed to mobilize energy for action (example: heart) and deactivates those not needed (example: gut).

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