The twelve cranial nerves and their origins are given below:

I-Olfactory nerve; origin: frontal lobe

II-Optic nerve; origin: thalamus

III-Ophthalmic nerve; origin: midbrain

IV-Trochlear nerve; origin: midbrain

V-Trigeminal nerve; origin: pons

VI-Abducens nerve; origin: pons

VII-Facial nerve; origin: pons

VIII-Vestibulocochlear nerve; origin: pons

IX-Glossopharyngeal nerve; origin: medulla

X-Vagus nerve; origin: medulla

XI-Spinal Accessory nerve; origin: medulla

XII-Hypoglossal nerve; origin: medulla

The nerves to originate in the pons are V, VI, VII, and VIII (the trigeminal, abducens, facial, and vestibulocochlear nerves).

The parasympathetic nervous system is responsible for the "rest and digest" mechanism. When the body is at rest the following occurs: pupils constrict (ophthalmic branch of the trigeminal nerve), lacrimation and salivation occur (facial nerve and glossopharyngeal nerve), heart rate decreases, respiration rate decreases, and digestion increases (vagus nerve).

In addition to the cranial nerves, sacral nerves 2-4 (pelvic splanchnic nerves) carry parasympathic fibers that control erections, the bladder, and the bowels.

The facial nerve (CN VII) is responsible for the sensation of taste on the anterior two-thirds of the tongue. CN IX, the glossopharyngeal nerve, is responsible for posterior sensation. CN V, the trigeminal nerve, is also involved in certain sensations throughout the tongue.

There are twelve cranial nerves. They are given in order below, with their associated functional classes.

CN I - olfactory nerve - sensory

CN II - optic nerve - sensory

CN III - occulomotor nerve - motor

CN IV - trochlear nerve - motor

CN V - trigeminal nerve - both sensory and motor

CN VI - abducens nerve - motor

CN VII - facial nerve - both sensory and motor

CN VIII - vestibulocochlear nerve - sensory

CN IX - glossopharyngeal nerve - both sensory and motor

CN X - vagus nerve - both sensory and motor

CN XI - accessory nerve - motor

CN XII - hypoglossal nerve - motor

Cranial nerves 3, 7, 9, and 10 are all responsible for parasympathetic nuclei of the brainstem. Oculomotor CN 3 contains the Edinger-Westphal nucleus which controls the eye smooth muscles (which if damaged would result in a dilated pupil that would not constrict in bright light). Facial CN 7 controls the superior salivatory nucleus which controls the submandibular, sublingual, and lacrimal gland secretion. Glossopharyngeal CN 9 innervates the parotid gland secretions. The vagus CN 10 innervates the heart and lungs down into the chest cavity. Helpful hint** - Students often confuse the superior and inferior salivatory nuclei, remember that on the brainstem the facial nerve exits superior to the glossopharyngeal nerve and thus how it is properly named for their nuclei.