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
Widening (computer science) Widening (computer science) In computer science, especially model checking and abstract interpretation, widening refers to at least two different techniques in the analysis of abstract transition systems where infinite progressions of abstract states are replaced by a (computed or guessed) least fixed point. The use of the term in "model checking" is closely related to "acceleration" techniques, some authors reserving "acceleration" for exact computations. While many computer programs can be understood in terms of machine states and transitions (see formal semantics of programming languages), their state spaces may be too large to fully represent and analyse. Modern analysis techniques therefore