Mydriasis iris sphincter, composed of circularly arranged muscle fibers, and the iris dilator, composed of radially arranged muscle fibers. The sphincter is innervated by (signaled by nerves of) the parasympathetic nervous system, and the dilator by the sympathetic nervous system. Sympathetic stimulation of the adrenergic receptors causes the contraction of the radial muscle and subsequent dilation of the pupil. Conversely, parasympathetic stimulation causes contraction of the circular muscle and constriction of the pupil. The mechanism of mydriasis depends on the agent being used. It usually involves either a disruption of the parasympathetic nerve supply to the eye (which normally constricts the
(What Is) Love? she was dissatisfied with the circumstances, but was in "no way dissing Lopez." A mastered version of "What Is Love?" was included on the soundtrack to "The Back-up Plan" (2010), a film in which Lopez stars. "What Is Love?" was re-titled as "(What Is) Love?" and appeared on "Love?" (2011). "(What Is) Love?" was due to be released as a promotional single from "Love?" on April 26, 2011, but was "unlocked" and released four days earlier, on April 22, 2011 by through a campaign on Lopez's Facebook page. It was released in many European countries on April 25. The song