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) of their new album to be released in Ireland on 20 February 2015, in the UK on 23 February 2015 and in the US on 24 February 2015. And as they borrowed the title from "The Second Coming", one of W. B. Yeats poems, the first Irishman to be awarded the Nobel Prize for Literature in 1923. Altan's official website published a presentation of their new studio album "The Widening Gyre" giving many details about the new album: the new musical direction taken by the band, the album recording process and the participation of numerous guest musicians as well as