Download Posterior View of the Brainstem, Regions which Supply Cranial

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Profesor: Dr. Martinez Sandoval
Posterior View of the Brainstem
Origin of the Cranial Nerves
Basilar Sulcus for the basilar artery
Lateral surfaces of pons, left and right.
On lateral surface of the pons, is the exit point for the trigeminal nerve with two branches, the 1)sensory and
the 2) motor root. the sensory root is wider and thicker. the motor root is very thin. It is primarily a sensory
nerve, and motor component is very small.
Abducent nerve is at the level of the pontomedullary surface. This nerve moves eye laterally.
Lateral fossa is on the lateral side of the pontomedullary surface. This transmits three nerves: 1) the facial
nerve (CNVII), the 2) intermediate nerve is part of the facial system, and 3) the auditory nerve, made up of
two parts: a) vesitublary division and b) auditory division.
Medulla. Has anterior medial sulcus. At the lowest part it is interrupted by a group of axons that will form a
decusation. This is where spinal nerves pass into the cerebral cortex.
Pyramid cords: On each side of the medial sulcus, see two cords on right and left. Each pyramid contains 1
million axons interiorly. The right corticospine will pass to the left (opposite side from where it began.)
Hypoglossal sulcus transmits the roots of the hypoglossal nerve (CNXII). This is the nerve to the tongue.
Two movements: protrusion and retraction. Protrusion is when you take out the tongue, caused by the
genioglossus muscle. The right and left genioglossus muscles push forward medially for protrusion.
Retraction is when you bring in the tongue, caused by the hypoglossus muscle.
Inferior Olive.
Dorsal Collateral Sulcus of Medulla. Region posterior to the inferior olive transmits CNs IX
(Glossopharangeal), X (Vagus), XI (Spinal Accessory).
Glossopharangeal. Helps with swallowing process.
Vagus. Supplies the laryngeal muscles to produce the voice.
Spinal Accessory. Supplies trapezius m., for shrugging, and sternoclanomastoid m., most powerful muscle of
neck which moves chin contralaterally.
4th ventricle. Cavity anteriorly formed by dorsal surface of pons/medulla. Posteriorly bounded by the
cerebellum.
Cerebral aqueduct. Lies between two diencephelon. Leads to the 4th ventricle.
Regions which supply cranial nerves:
Medulla: CN's 9, 10, 11, 12.
Pons: CN's 5, 6, 7, 8
Midbrain: CN's 3 and Trochlear
Horizontal Section of Midbrain at Level of the Superior Colliculus
Oculomotor nerve elevates, abducts, depresses eye and opens palpibral fissure.
Nucleus of papila converges the eye.
Red Nucleus is huge structure. It gives origin to important descending vasiculus, known as Rubro spinal tract.
Axons go along midline and then descend.
Decusation of Forel. Where axons of rubro spinal tract cross before descending.
Horizontal Section of Midbrain at Level of the Inferior Colliculus
Inferior colliculus.
Nucleus of the trochlear. Gives origin to axons that will leave the midbrain dorsally.
Decusation of Brachium Conjunctivum or Wernekink Decusation. The hand out calls it Superior cerebellar
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peduncle. Origin of this huge decusation is from descending cerebral cortex motor axons. Controls muscular
coordination. Different regions of this huge decusation:
Corticospinal system-These are descending axons and decusate into the lowest part of the medulla. Lesion
here causes paralysis. These descending axons come from coronal radiata and pass through internal capsule
into cerebral peduncle and then the pons. The millions of axons that descend stop in the pons.
Corticopontin nuclei is where descending axons stop. This region sends pontocerebella axons into the
cerebellum. Right and left sides of the cerebellar cortex send ascending projections which cross each other as
pass superiorly.
Cerebellar rubral axons pass from the cerebellum to the red nucleus. These cerebellar rubral axons ascend,
crossing, to become...
Rubro spinal tract.
Horizontal Section at Level of Upper Half of Pons
Corticospinal system.
Pontin nuclei. Nuclei interspersed between corticospinal and corticopontin. They will exit from left and right
sides to cross contralaterally to reach the cerebellum.
Main Sensory Nucleus of Trigeminal Nerve. Receives light touch sensations from the head and part of the
neck.
Motor Trigeminal Nucleus or Masticatory Nucleus. Medial to main sensory nucleus of trigeminal nerve.
Supplies masticatory muscles.
Horizontal Section at Level of Lower Half of Pons (Almost at level of Medulla)
4th Ventricle. See above.
Nucleus of Abducent Nerve. Controls abduction of eye (moves eye laterally). Axons leave anteriorly and
emerges from the brainstem at the level between pons and reach pontomedullary sulcus for exit.
Facial nucleus. Supplies superficial muscles of the face. Controls mimetic aspects, or facial expressions, of
the face.
Descending Spinal trigeminal nucleus. Longest of all nuclei in the brainstem. Receives light touch, pain and
temperature from the entire head and part of the neck.
Dorsal View of Superior and Inferior Colliculus
Main Sensory Nucleus of Trigeminal Nerve. Reaches medially to the ophthalmic division (V1)
maxillary (V2), and mandibullary (V3). Descending Spinal Trigeminal Nucleus. Very long because can see
part of it in the pons and reaches level C5-C6, becoming the substancia gelatinosa in the spinal cord.
Trigeminal branches form from unipolar cells. Peripheral processes form the ophthalmic, maxillary, and
mandibullary nerves. There is also a central process which form main sensory root to convey light touch
impulses. It doesn't matter if another cranial transmits pain, because they must send info through the spinal
trigeminal nucleus at the end. Descending branches transmit pain/temperature.
Horizontal Section of the Medulla
Hypoglossal nucleus. Send axons laterally to the hypoglossal sulcus to supply the geneoglossus and the other
16 pairs of muscles in the tongue.
Dorsal Motor Nucleus of CNX (Vagus N). Lateral to the hypoglossal nucleus. 27mm in length. Extend
almost across the medulla. It is the origin of the Vagus Nerve, which supplies most of the parasympathetic
innervation of the visceral regions of the body.
Solitary nucleus. Lateral to the dorsal motor nucleus. 30mm in length (long). Begins at level of junction
between medulla and spinal cord. Descends on both sides of the medulla to join at the inferior region, at the
Comissure Nucleus of Cajal.
Gustatory Nucleus of Nageotte. Upper part of solitary nucleus. Receives spacial visceral afferent (SVA),
taste and visceral sensations.
Vestibular area. Controls equilibrium.
Nucleus Ambiguus. 28mm in length and thin. Three parts: 1) Superior for Glossopharangeal N, 2) Middle for
Vagus N, and 3) Inferior for Spinal Accessory N.