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
Batman: The Widening Gyre Batman: The Widening Gyre Batman: The Widening Gyre is the title of a 6-issue comic book limited series starring Batman, released August 2009 through July 2010. The series is written by Kevin Smith and illustrated by Walt Flanagan. The title is a reference to the William Butler Yeats poem "The Second Coming". The series was initially planned as 12 issues, with a long break planned between issues six and seven. After issue six was published, Smith and Flanagan's work on their reality show, "Comic Book Men", extended this planned break further than expected. It was decided in the interim to