Final answer:
Splanchnic nerves include preganglionic fibers that synapse with collateral ganglia, which are part of the sympathetic nervous system, controlling organs within the abdominal cavity.
Step-by-step explanation:
The splanchnic nerves include preganglionic fibers that go to collateral ganglia. These nerves do not synapse in the chain ganglia; instead, they project onto one of the collateral ganglia such as the celiac ganglion, the superior mesenteric ganglion, or the inferior mesenteric ganglion. The collateral ganglia are part of the sympathetic nervous system and are essential for controlling organs within the abdominal cavity. Specifically, the greater splanchnic nerve contains fibers that synapse with the celiac ganglion, while the lesser splanchnic nerve fibers project onto the inferior mesenteric ganglion.
The splanchnic nerves are associated with the sympathetic division of the autonomic nervous system. This system contrasts with the parasympathetic division, where preganglionic fibers from cranial and sacral regions project to terminal ganglia that are often close to or within the target organ, making the postganglionic fibers short.