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 Widening Gyre (album) there some of the fourteen tracks of this superb album. [...] Throughout the album, American and Irish tunes intertwine with each other and lay down a wonderful template sublimated by Mairéad Ní Mhaonaigh's crystalline voice and her fellow musicians' instruments. Once again, a nice piece of work." In December 2015, The Telegraph's culture editor Martin Chilton chose "The Widening Gyre" as one of the 70 best folk music albums of the year 2015. On 7 March 2015, "The Widening Gyre" entered the Billboard Top Ten World Music Albums Charts at #5 (its peak position ever) and hold #5 for six