Nucleus of oculomotor nerve

The nucleus of oculomotor nerve, also known as the main oculomotor nucleus, is a crucial somatic motor nucleus within the oculomotor nerve complex, playing a vital role in eye movement and coordination.

Location: The nucleus of oculomotor nerve is situated in the anterior part of the gray matter surrounding the cerebral aqueduct of the midbrain. It lies at the level of the superior colliculus and integrates a variety of visual and motor inputs to facilitate precise ocular control.

Structure and Function: The nucleus consists of nerve cells responsible for innervating all the extrinsic muscles of the eye, except the superior oblique and the lateral rectus muscles. Specifically, the nucleus of oculomotor nerve controls the levator palpebrae superioris, superior rectus, medial rectus, inferior rectus, and inferior oblique muscles. These muscles are fundamental for movements such as lifting the upper eyelid and directing the eye upward, downward, and medially.

Pathways: Outgoing fibers from the nucleus of oculomotor nerve move anteriorly through the red nucleus and emerge on the midbrain's anterior surface within the interpeduncular fossa. These nerve fibers form an essential part of the oculomotor nerve, along with their parasympathetic counterparts from the Edinger-Westphal nucleus. They travel through the cavernous sinus and pass through the superior orbital fissure to reach the orbital cavity, where they innervate the aforementioned extraocular muscles.

Afferent connections: The nucleus of oculomotor nerve receives several important afferent connections:

• Corticonuclear fibers: The nucleus receives bilateral cortical input from both cerebral hemispheres through corticonuclear fibers.

• Tectobulbar fibers: These fibers from the superior colliculus convey visual information from the visual cortex.

• Medial longitudinal fasciculus (MLF): This crucial pathway establishes connections with the nuclei of the fourth, sixth, and eighth cranial nerves, facilitating coordinated eye movements.