Pons.html



Brain: Pons
Diagram showing the positions of the three principal subarachnoid cisternæ. (Pons visible at center.)
Anteroinferior view of the medulla oblongata and pons.
Gray's	subject #187 785
Part of	Brain stem
Artery	pontine arteries
Vein	transverse and lateral pontine veins
NeuroNames	hier-538
MeSH	Pons

The pons (sometimes pons Varolii after Costanzo Varolio) is a structure located on the brain stem. It is cranial 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

The pons relays sensory information between the cerebellum and cerebrum; aids in relaying other messages in the brain; controls arousal, and regulates respiration (see respiratory centres). In some theories, the pons has a role in dreaming.¹

Anatomy of the pons

The "knob-like" process (Basal pons) 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:²

• 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)

Related diseases

• Central pontine myelinosis, a demyelination disease that causes difficulty with sense of balance, walking, sense of touch, swallowing and speaking to mention just a few symptoms. In a clinical setting it is often associated with transplant. Undiagnosed it can lead to death or 'locked in' syndrome.

Additional images

Scheme showing the connections of the several parts of the brain.	Superficial dissection of brain-stem. Lateral view.	Superficial dissection of brain-stem. Ventral view.	Coronal section of the pons, at its upper part.
Dissection showing the projection fibers of the cerebellum.	Sagittal section through right cerebellar hemisphere. The right olive has also been cut sagitally.	Scheme of roof of fourth ventricle. The arrow is in the foramen of Majendie.	Mesal aspect of a brain sectioned in the median sagittal plane.
Coronal section of brain immediately in front of pons.	Hind- and mid-brains; postero-lateral view.	Median sagittal section of brain.	Dissection showing the course of the cerebrospinal fibers.
Terminal nuclei of the cochlear nerve, with their upper connections.	Terminal nuclei of the vestibular nerve, with their upper connections.	The hypophysis cerebri in position. Shown in sagittal section.	Pituitary and pineal glands
Axial section of the Brainstem (Pons) at the level of the Facial Colliculus	Human cerebrum lateral view	Human brain frontal (coronal) section	Human brainstem anterior view

References

1. ^ The "Science of Dreaming" in Neurontic: Psychology for the Modern Mind..
2. ^ Physiology at MCG 4/4ch6/s4ch6_10

External links

• Diagram at UCC
• BrainMaps at UCDavis Pons