Mydriasis eye, and also to reduce painful ciliary muscle spasm (see cycloplegia). One effect of administration of a mydriatic is intolerance to bright light (photophobia). Purposefully-induced mydriasis via mydriatics is also used as a diagnostic test for Horner's syndrome. Mydriasis can be induced via modulation of adrenergic or cholinergic signalling. Within the adrenergic system, norepinephrine is a hormone and neurotransmitter responsible for regulating physiological processes in the body, including the involuntary muscles of the autonomic nervous system (such as the dilation or constriction of the pupil aperture via the muscles of the iris). Modulation of norepinephrine signalling can induce mydriasis. For
Normally hyperbolic invariant manifold 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 assume that the dynamics of formula_1 itself is neutral compared with the dynamics nearby, which is not allowed for a hyperbolic set. NHIMs were introduced by Neil Fenichel in 1972. In this and subsequent papers, Fenichel proves that NHIMs possess stable and unstable manifolds and more importantly, NHIMs and their stable and unstable manifolds persist under small