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
The World Is What It Is in 1996. The biography has been extensively reviewed: the reviewers include Paul Theroux, who wrote an earlier book about Naipaul. The biography was selected by the editors of the "New York Times Book Review" as one of the "Times"' "10 Best Books of 2008". It won the 2008 National Book Critics Circle Award in Biography, and the British literary award the Hawthornden Prize. The World Is What It Is The World Is What It Is: The Authorized Biography of V. S. Naipaul is a biography of the Nobel Prize-winning author V. S. Naipaul by Patrick French. It was published in