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
Into the Widening World Into the Widening World Into the Widening World is a collection of 26 short fictional coming-of-age stories. It was written by many authors including: Nadine Gordimer, Ben Okri, Bharati Mukherjee, Alice Munro and Gabriel Garcia Marquez. "Columba"- Michelle Cliff "Weight-Reducing Diet"- Jorge Edwards "On Sunday"- Mario Vargas "Artificial Roses"- Gabriel Garcia Marquez "The Raffle"- V. S. Naipaul "Exchange Value"- Charles Johnson "Borders"- Thomas King "Saints"- Bharati Mukherjee "The Turkey Season"- Alice Munro "The Gifts of War"- Margaret Drabble "The Nothingness Forest"- Margareta Ekstrom "Christmas"- John McGahern "That Wall, That Mimosa"- Merce Rodoreda "Date with a bird"- Tatyana Tolstaaya "Turkish Soldier