From Wikipedia, the free encyclopedia
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.
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]
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]
A number of cranial nerve nuclei are present in the pons:
Scheme showing the connections of the several parts of the brain.
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Superficial dissection of brain-stem. Lateral view.
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Superficial dissection of brain-stem. Ventral view.
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Coronal section of the pons, at its upper part.
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Dissection showing the projection fibers of the cerebellum.
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Sagittal section through right cerebellar hemisphere. The right olive has also been cut sagitally.
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Scheme of roof of fourth ventricle. The arrow is in the foramen of Majendie.
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Mesal aspect of a brain sectioned in the median sagittal plane.
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Coronal section of brain immediately in front of pons.
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Hind- and mid-brains; postero-lateral view.
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Median sagittal section of brain.
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Dissection showing the course of the cerebrospinal fibers.
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Terminal nuclei of the cochlear nerve, with their upper connections.
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Terminal nuclei of the vestibular nerve, with their upper connections.
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Pituitary and pineal glands
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Axial section of the Brainstem (Pons) at the level of the Facial Colliculus
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- ^ The "Science of Dreaming" in Neurontic: Psychology for the Modern Mind..
- ^ Physiology at MCG 4/4ch6/s4ch6_10
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Brain: rhombencephalon (hindbrain) |
| Myelencephalon/medulla |
anterior/ventral: Arcuate nucleus of medulla • Pyramid (Decussation) • Olivary body • Inferior olivary nucleus • Anterior median fissure • Ventral respiratory group
posterior/dorsal: VII,IX,X: Solitary/tract • XII, X: Dorsal • IX,X,XI: Ambiguus • IX: Inferior salivatory nucleus • Gracile nucleus/Cuneate nucleus/Accessory cuneate nucleus • Area postrema • Posterior median sulcus • Dorsal respiratory group
raphe/reticular: Sensory decussation • Reticular formation (Gigantocellular nucleus, Parvocellular reticular nucleus, Ventral reticular nucleus, Lateral reticular nucleus, Paramedian reticular nucleus) • Raphe nuclei (Obscurus, Magnus, Pallidus)
tracts: Corticospinal tract (Lateral, Anterior) • Inferior cerebellar peduncle • Olivocerebellar tract • Spinocerebellar (Dorsal, Ventral) • Spinothalamic tract • PCML (Posterior external arcuate fibers, Internal arcuate fibers, Medial lemniscus) • Extrapyramidal (Rubrospinal tract, Vestibulospinal tract, Tectospinal tract)
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| Metencephalon/pons |
anterior/ventral: Superior olivary nucleus • Basis pontis (Pontine nuclei, Middle cerebellar peduncles)
posterior/dorsal: Pontine tegmentum (Trapezoid body, Superior medullary velum, Locus ceruleus, MLF, Vestibulocerebellar tract, V Principal Spinal & Motor, VI, VII, VII: Superior salivary nucleus) • VIII-c (Dorsal, Anterior)/VIII-v (Lateral, Superior, Medial, Inferior)
raphe/reticular: Reticular formation (Caudal pontine reticular nucleus, Oral pontine reticular nucleus, Tegmental pontine reticular nucleus, Paramedian pontine reticular formation) • Median raphe nucleus
Apneustic center • Pneumotaxic center
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| Metencephalon/cerebellum |
Vermis • Flocculus • Arbor vitae • Cerebellar tonsil • Inferior medullary velum
Molecular layer (Stellate cell, Basket cell, Parallel fiber) • Purkinje cell layer (Purkinje cell) • Granule cell layer (Golgi cell) • Mossy fibers • Climbing fiber
Deep cerebellar nuclei (Dentate, Emboliform, Globose, Fastigial) |
| Fourth ventricle |
apertures (Median, Lateral) • Rhomboid fossa (Vagal trigone, Hypoglossal trigone, Obex, Sulcus limitans, Facial colliculus, Medial eminence) • Lateral recess |