The superior tarsal muscle receives its innervation from the sympathetic nervous system.

Postganglionic sympathetic fibers originate in the superior cervical ganglion, and travel via the internal carotid plexus, where small branches communicate with the oculomotor nerve as it passes through the cavernous sinus.

Its role is not fully clear, but may be an accessory muscle to raise the upper eyelid.

[2] Damage to some elements of the sympathetic nervous system can inhibit this muscle, causing a drooping eyelid (partial ptosis).

Given the possible confusion, the use of the term Müller's muscle should be discouraged unless the context removes any ambiguity.