What is the principal nerve in human body?

The vagus nerve is the tenth cranial nerve, and it is the principal nerve of the parasympathetic nervous system. It originates in the medulla oblongata of the brainstem and travels through the neck and thorax to the abdomen. The vagus nerve provides innervation to a wide range of organs and tissues, including the heart, lungs, stomach, and intestines. It also plays a role in regulating the immune system and the body's response to stress. The vagus nerve has been shown to have a number of important health benefits, including reducing inflammation, improving digestion, and boosting mood.