We will now turn our attention from the sympathetic division of the ANS to the parasympathetic portion. The parasympathetic division of the ANS is sometimes called the craniosacral outflow because the cell bodies of presynaptic parasympathetic neurons are located in the brainstem (nuclei of cranial nerves III, VII, IX, and X) and in the lateral horn of spinal cord segments S2, S3, and S4. In spinal cord segments T1-L2 the lateral horn is home to the cell bodies of presynaptic sympathetic neurons. The lateral horn is absent from L3-S1, but reappears in segments S2, S3 and S4 to house the cell bodies of presynaptic parasympathetic fibers. In general, when "the lateral horn" is mentioned, it refers to the T1-L2 sympathetic lateral horns, but don't get confused by the presence of a parasympathetic lateral horn in segments S2, S3 and S4.

The parasympathetic system is much more limited in its distribution as compared to the sympathetic nervous system. The parasympathetic system distributes fibers to viscera of the head, thorax, abdomen, and pelvis. The parasympathetic nervous system does NOT reach the body wall, and NO parasympathetic innervation reaches the limbs. It is particularly important to note that the parasympathetic nervous system does not innervate peripheral blood vessels.