What type of fibers are associated with the parasympathetic nervous system?

The correct choice, cholinergic fibers, refers to the fibers that release the neurotransmitter acetylcholine in the parasympathetic nervous system. This system is responsible for the 'rest and digest' functions of the body, promoting activities that conserve energy and enhance digestion. Cholinergic fibers can be found in both preganglionic neurons, which originate in the central nervous system and synapse with postganglionic neurons, as well as in postganglionic neurons, which directly innervate target organs.

In contrast, adrenergic fibers are associated with the sympathetic nervous system and release norepinephrine, leading to a 'fight or flight' response. Inotropic refers to the force of muscle contraction, particularly in cardiac muscles, and is not related to the neurotransmitter systems. Corticosteroids are a class of steroid hormones that may affect numerous physiological functions but do not pertain to the nervous system's fiber types. Therefore, the designation of cholinergic fibers is a defining characteristic of the parasympathetic nervous system's operations and functionality.