Final answer:
Sympathetic postganglionic neurons that innervate abdominopelvic organs are called ganglia, specifically collateral or prevertebral ganglia.
Step-by-step explanation:
Groups of sympathetic postganglionic neurons innervating abdominopelvic organs are called ganglia. In the sympathetic division of the autonomic nervous system, the postganglionic fibers are the axons from ganglionic neurons that project to target effectors, which directly influence the organ. These fibers, compared with preganglionic fibers, are long and unmyelinated due to the greater distance from the ganglion to the target effector.
The collateral ganglia, also known as prevertebral ganglia, are situated anterior to the vertebral column and control organs within the abdominal cavity. The three main collateral ganglia are the celiac ganglion, the superior mesenteric ganglion, and the inferior mesenteric ganglion. They receive inputs from splanchnic nerves and central sympathetic neurons, and are part of the enteric nervous system.