System

a. Cell bodies of the first neurons of the parasympathetic NS make up the inter-mediolateral gray columns in the sacral spinal cord at the S-2, S-3, and S-4 levels. See paragraph 11-17a above for the position of the intermediolateral gray columns. Cell bodies of the first neurons also make up four pairs of nuclei in the brainstem; these nuclei are associated with cranial nerves III, VII, IX, and X. Here, we are speaking of preganglionic parasympathetic neurons.

b. Cell bodies of the second neurons make up intramural ganglia within the walls of the visceral organs. These second neurons innervate the central visceral organs. They do NOT innervate peripheral visceral organs. Here, we are speaking of the post-ganglionic parasympathetic neurons.

c. The parasympathetic NS has the opposite effect on visceral organs from that of the sympathetic NS. (Example: The heart is accelerated by the sympathetic NS and decelerated by the parasympathetic NS.)

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