Final answer:
The nerves described are part of the sympathetic nervous system, which innervate organs via branching from spinal nerves that form nerve plexuses.
Step-by-step explanation:
The structures described in the question are part of the sympathetic nervous system. Spinal nerves branch out from the spinal cord and consist of both sensory and motor axons. These spinal nerves can enter into a nerve plexus, a network of interconnected nerve fibers that rearrange before branching off again. The question specifically describes a scenario where the nerves innervate a “trunk” that parallels the spinal cord before branching off the trunk, which is a characteristic mainly associated with the sympathetic nervous system.
This system is responsible for the “fight or flight” response and innervates various organs throughout the body. To provide an example, the brachial plexus which originates from spinal nerves in the cervical region, reorganizes axons from these spinal nerves to innervate the arms. This illustrates how spinal nerves from segments can combine and redistribute through plexuses to innervate specific body parts.