Final answer:
The cranial nerve in question is the vagus nerve, also called the tenth cranial nerve, which carries parasympathetic fibers that innervate the thoracic and upper abdominal viscera. It arises from the medulla of the brain stem and regulates critical functions such as heart rate, digestion, and breathing.
Step-by-step explanation:
The cranial nerve that is a mixed parasympathetic nerve and innervates the abdominal and thoracic viscera is known as the vagus nerve, or the tenth cranial nerve. This nerve is responsible for the autonomic control of organs in the thoracic and upper abdominal cavities. It arises from the medulla of the brain stem and sends fibers that control various vital functions such as heart rate, digestion, and respiratory rate.
The vagus nerve contains parasympathetic fibers that extend from the mid-thoracic to the lower thoracic region, regulating the function of internal organs. Neurons in the dorsal nucleus of the vagus nerve project through this nerve to terminal ganglia located in the thoracic and abdominal cavities, influencing the heart, bronchi, esophagus, stomach, liver, pancreas, gall bladder, and small intestine. Moreover, this nerve plays a significant role in the cranial component of the parasympathetic nervous system, which is essential for maintaining homeostasis in the body.