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The Midbrain

Also imbedded in the white matter of the midbrain are two pigmented nuclei, the substantia nigra and the red nucleus

The Midbrain

The substantia nigra is a bandlike nucleus located deep to the cerebral peduncle

It is the largest

nuclear mass in the midbrain

The Midbrain

Its dark color reflects its high content of melanin pigment, a precursor of dopamine a neurotransmitter released by these neurons

The substantia nigra is functionally linked to the basal nuclei of the cerebral hemispheres

The Midbrain

The red nucleus is found between the substantia nigra and the cerebral aqueduct

It reddish hue is due to its vascular supply and the presence of iron pigment in the cell bodies of its neurons

The Midbrain

The red nuclei are relay nuclei in some descending motor pathways that effect limb flexion

The red nuclei is the largest nucleus in the reticular formation, a system of small nuclei scattered through the core of the brain stem

The Pons

Pons

The pons is the bulging brain stem region wedged between the midbrain and the medulla oblongata

The Pons

It forms part of the anterior wall of the fourth ventricle

It is chiefly composed of conduction tracts

The deep projection

fibers run

longitudinally and Pons complete the

pathway between higher brain centers and spinal cord

The Pons

The deep projection fibers run longitudinally and complete the superior­inferior pathway between

the higher brain

centers and the Pons spinal cord

The Pons

The more superficial nuclei are relays for conversations between the motor cortex and the cerebellum

These fibers are orientated dorsally and transversely and connect the pons bilaterally with the cerebellum

Middle Cerebellar peduncles

The Pons

Several cranial nerves issue from pons nuclei

Trigeminal nerve

Abducens nerve

Facial nerves

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