Final answer:
The correct term for the nerve providing sensations from the gastrointestinal tract and associated with the parasympathetic system is CN X, Vagus. The vagus nerve plays a crucial role in autonomic functions within the thoracic and superior abdominal cavities and aids in taste sensations and swallowing.
Step-by-step explanation:
The term that best defines sensations from the gastrointestinal tract provided by a nerve related to the parasympathetic system is CN X, Vagus. The vagus nerve is known for its autonomic functions in the thoracic and superior abdominal cavities and contains preganglionic parasympathetic fibers that are essential for various visceral functions.
The vagus nerve is involved in conveying taste sensations related to the gag reflex and directly stimulates the contraction of skeletal muscles in the pharynx and larynx, which contributes to swallowing and speech functions. It's part of the cranial nerves that contain both sensory and motor fibers, specifically serving the head and neck for autonomic (parasympathetic) functions.