Final answer:
The parasympathetic changes in activity induce vasodilation and an increase in GI blood flow, enhancing digestion by increasing GI secretion and motility.
Step-by-step explanation:
The question discusses the effects of the parasympathetic nervous system on the gastrointestinal (GI) tract. The parasympathetic nervous system is part of the autonomic nervous system that manages the body's rest-and-digest activities. When the parasympathetic nervous system is activated, it induces vasodilation which is the widening of blood vessels, and an increase in blood flow, particularly in the GI tract. This facilitates digestion by increasing GI secretion and motility. The parasympathetic responses also include slowing down the heart rate and reducing blood pressure. Acetylcholine is a neurotransmitter that plays a significant role in promoting these parasympathetic effects.