Oculomotor nerve


There are some movements of the eyeball, of both intrinsic and extrinsic nature, that rely completely on the oculomotor nerve for their motor function. These vital nerve impulse originate from the nuclei within the midbrain and are transported via the oculomotor nerve, which is basically a motor nerve. Once the oculomotor nerve reaches the superior orbital fissure it branches out into the superior and inferior branches of itself. The superior branch is responsible for providing innervation to the superior rectus muscle.


This muscle gives the eyeball the ability to move superiorly. Addiotnally, the superior branch provides innervation to the levator palpebrae superioris muscles, which is the muscle which provides that eyelid with the ability to open, shut, and raise. The inferior branch then innervates the muscles which provide the eyeball with the freedom to move inferiorly, laterally, medially, and basically all around.

These muscles are known as the medial rectus (medial movement,) inferior rectus ( superior movement,) and the inferior oblique (lateral movement) of the eye.


Oculomotor nerve
Image: Oculomotor Nerve

The fibers related to the oculomotor nerve are really quite busy. First, they enter the eyeball for the intention of providing parasympathetic autonomic motor innervation directed toward the internal smooth muscles which belong to the pupil’s iris. This allows for the necessary constriction of this muscle.


The fibers of the oculomotor nerve are also responsible for the muscles which are positioned within the ciliary body, which are controlled to support the optic lens. The proprioceptors of the internal (intrinsic) muscles of the eyeball yield a few additional sensory fibers of the oculomotor nerve.

These fibers are vital in the communication of impulses in relation to the muscles they serve, dealing entirely with the position and activity of these delicate muscles surrounding the eyeball. Drooping eyelids and permanently dilated pupils are most likely the result of damage to the oculomotor nerve. A human eyeball with a distressed oculomotor nerve is likely to have limited range of eyeball motion.
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