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) critic Lee Zimmerman, stating: ""The Widening Gyre" is a defining moment for Altan. [...] [It] is much more than a mere scholarly treatise. The energy and enthusiasm are palatable, and there's a sense of celebration that echoes throughout. [...] Altan has made the kind of album that defines them as distinctive." "Irish Music Magazine"'s critic Eileen McCabe, stated: "Altan are just at the start of their next chapter and having shown their inimitable metal with "The Widening Gyre"; they have set the standard at an all time high." "Folkworks" reviewer Anya Sturm, stated: "Altan's new CD "The Widening Gyre" is