Final answer:
Parasympathetic preganglionic cell bodies are located in the brainstem and the sacral spinal cord, and they are a crucial element of the parasympathetic nervous system which governs the body's rest and digest processes.
Step-by-step explanation:
The parasympathetic preganglionic cell bodies are located in two specific regions of the central nervous system: the brainstem and the sacral spinal cord. The preganglionic neurons in the parasympathetic nervous system play a crucial role in the 'rest and digest' responses of the body. These neurons initiate in nuclei of the brainstem or in the lateral horn of the sacral spinal cord, projecting to terminal ganglia that are near or within the target organs they regulate.