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
Here Is What Is Here Is What Is Here Is What Is is the fifth studio album by Canadian songwriter and record producer Daniel Lanois. It was first released in December 2007 as a high-quality download, and later released on CD on March 18, 2008. The album is the result of the same project that led to the 2007 documentary "Here Is What Is" that premiered at the 2007 Toronto International Film Festival in September. The movie documents the aesthetics and creative process behind Lanois' approach to music making and recording. The album has been presented as a direct soundtrack to this film, and