Pons

Overview
The pons (sometimes pons Varolii after Costanzo Varolio) is a structure located on the brain stem. It is rostral to the medulla oblongata, caudal to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it is above the medulla, below the midbrain, and anterior to the cerebellum.

Function
It is part of the central nervous system, and relays sensory information between the cerebellum and cerebrum. Aids in relaying messages in the brain, and contains the pneumotaxic centres that help regulate respiration. Also controls arousal. Some theories pose that it has a role in dreaming.

Anatomy of the pons
The "knob-like" process is 2 centimeters long and located on the anterior (front) of the brainstem. It is formed of nerves that travel from one side (left or right) to the other. Most other fibres in the brainstem travel up and down.

The posterior (back) surface of the pons forms part of the wall of the fourth ventricle of the brain.

Most blood to the pons is supplied by pontine arteries. These are small arteries that branch off the basilar artery (of the Circle of Willis). Blood also comes from the anterior inferior, and superior cerebellar arteries.

There are two main domains in the pons for control of respiration:
 * the apneustic center - lower pons
 * the pneumotaxic center - upper pons

Cranial nerve nuclei
A number of cranial nerve nuclei are present in the pons:
 * mid-pons: The chief or pontine nucleus of the trigeminal nerve sensory nucleus (V)
 * mid-pons: the motor nucleus for the trigeminal nerve (V)
 * lower down in the pons: abducens nucleus (VI)
 * lower down in the pons: facial nerve nucleus (VII)
 * lower down in the pons: vestibulocochlear nuclei (vestibular nuclei and cochlear nuclei) (VIII)