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) get their teeth into", describing "The Widening Gyre" as "an absolute treasure trove" and Ní Mhaonaigh's voice as "indescribably beautiful", "songs [occupying] a special place on any Altan album", adding: "Ní Mhaonaigh's soaring, soul-stirring vocals on "Far Beyond Carrickfinn" [...] is one of the most touching things you'll hear this year". The Telegraph gave it 4 stars (out of 5), describing it as "a wonderful mix of Irish and Appalachian music." On 9 March 2015, "The Widening Gyre" was honoured "album of the week" on RTÉ radio 1. PopMatters's gave it a rating of 8 stars out of 10. Music