Final answer:
Parasympathetic preganglionic nerves differ from sympathetic preganglionic nerves based on longer fibers, ganglia located close to or within targeted organs, and the neurotransmitter released by parasympathetic postganglionic nerves being ACh instead of norepinephrine.
Step-by-step explanation:
The three characteristics that differentiate parasympathetic preganglionic nerves from sympathetic preganglionic nerves are: the length of fibers, the location of ganglia, and the neurotransmitter released.
- Parasympathetic preganglionic fibers are long because their ganglia are located close to, or even within, their target organs, while sympathetic preganglionic fibers are shorter, with ganglia located further away along the spinal cord.
- The location of the ganglia for the parasympathetic system is near or within the target effector (often called intramural ganglia), whereas the sympathetic ganglia form a chain beside the spinal cord.
- Regarding the neurotransmitter, both parasympathetic and sympathetic preganglionic fibers release acetylcholine (ACh). However, the postganglionic fibers differ: parasympathetic postganglionic fibers release ACh, while most sympathetic postganglionic fibers release norepinephrine, with the exception of those projecting to sweat glands and blood vessels associated with skeletal muscles, which also release ACh.
The correct answer to the question is: Length of fibers, location of ganglia, neurotransmitter released.