Which cranial nerve, also designated as Cranial Nerve X, is the longest cranial nerve and supplies extensive parasympathetic innervation to the heart, lungs, and digestive tract?

Answer and explanation

Correct answer: D. Vagus nerve (CN X)

  1. Step 1: The vagus nerve emerges from the medulla oblongata and descends through the neck into the thorax and abdomen.
  2. Step 2: As the primary component of the parasympathetic autonomic nervous system, it slows heart rate, stimulates gastrointestinal peristalsis and gland secretions, and conveys visceral sensory feedback to the brainstem.
Answer
Vagus nerve (CN X)
Why not the others: 'Trigeminal nerve (CN V)' The trigeminal nerve provides sensory innervation to the face and motor innervation to muscles of mastication; 'Optic nerve (CN II)' The optic nerve is a purely sensory cranial nerve that transmits visual signals from the retina to the brain; 'Facial nerve (CN VII)' The facial nerve controls muscles of facial expression and conveys taste sensations from the anterior two-thirds of the tongue.

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