Final answer:
Intramural ganglia are terminal ganglia of the parasympathetic system located within the walls of the target effector, enabling close proximity to effector cells for optimized 'rest-and-digest' responses.
Step-by-step explanation:
Parasympathetic ganglia that supply fibers to effector cells at very close proximity are called intramural ganglia. These are a type of terminal ganglia of the parasympathetic system that are found within the walls of the target effector. This strategic location allows for shorter postganglionic fibers, as these ganglia are either near or embedded within the walls of organs, thus allowing precise control over the 'rest-and-digest' functions facilitated by the parasympathetic nervous system.