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
Normally hyperbolic invariant manifold the unstable bundle and denoted "E" and "E", respectively. With respect to some Riemannian metric on "M", the restriction of "Df" to "E" must be a contraction and the restriction of "Df" to "E" must be an expansion, and must be relatively neutral on formula_4. Thus, there exist constants formula_5 and "c" > 0 such that and Normally hyperbolic invariant manifold A normally hyperbolic invariant manifold (NHIM) is a natural generalization of a hyperbolic fixed point and a hyperbolic set. The difference can be described heuristically as follows: For a manifold formula_1 to be normally hyperbolic we are allowed to