What is distinctive about the preganglionic fibers of the sympathetic nervous system?

The preganglionic fibers of the sympathetic nervous system are distinctive because they are short. These fibers emerge from the thoracolumbar region of the spinal cord, specifically from the T1 to L2 segments. Due to the positioning of the sympathetic chain ganglia, which are located relatively close to the spinal cord, the preganglionic fibers do not need to travel long distances before synapsing with postganglionic neurons.

This structural characteristic plays a significant role in the function of the sympathetic nervous system, allowing for quick responses during the "fight or flight" reaction. The short length of these fibers contrasts with the longer postganglionic fibers, which extend from the ganglia out to target organs. Additionally, while it is true that they release acetylcholine at the neuroeffector junction, this is a function that they share with parasympathetic preganglionic fibers, not a unique characteristic of the sympathetic system's preganglionic fibers.