[UW Anatomy |
Contents]
Function:
Some cells in this complex possess axons that innervate extraocular
eye muscles (also levator palpebrae) except for lateral rectus and
superior oblique. Other cells are preganglionic parasympathetic that
possess axons which synapse in the ciliary ganglion and are involved
in constricting the pupil.
Pathway:
All axons (both somatic and autonomic) pass ventrally to exit the
midbrain between the cerebral peduncles (interpeduncular fossa).
Somatic fibers directly innervate eye muscles and levator palpebrae,
while preganglionic parasympathetic axons synapse within the ciliary
ganglion. Short postganglionic parasympathetic fibers then pass to
the sphincter pupillae (constrict pupil) of the iris and the ciliary
muscles.
Deficits:
Lesion of the oculomotor complex or its nerve fibers results in
atrophy of all muscles innervated, diplopia due to an outward and
slightly downward rotation of the eye (you must raise the eyelid to
see this), ptosis (levator) and a DILATED PUPIL. ALL PROBLEMS ARE
IPSI.
Other Note:
Parasympathetic fibers (lesion=dilated pupil) can be damaged without
somatic fiber involvement. C.N. III is stretched upon herniation of
IPSI. uncus and adjacent temporal lobe. Corticospinal fibers in the
opposite (CONTRA.) cerebral peduncle are damaged too! Thus dilated
pupil and hemiplegia are on SAME side (corticospinal fibers CROSS in
the pyr. dec.).