出典:Wiktionary
出典:『Wiktionary』 (2014/04/19 12:06 UTC 版)
出典:Wikipedia
出典:『Wikipedia』 (2011/07/22 14:24 UTC 版)
The iris dilator muscle (pupil dilator muscle, pupillary dilator, radial muscle of iris, radiating fibers), is a smooth muscle of the eye, running radially in the iris and therefore fit as a dilator. It has its origin from the anterior epithelium. It is innervated by the sympathetic system, which acts by releasing noradrenaline, which acts on α1-receptors. Thus, when presented with a threatening stimuli that activates the fight-or-flight response, this innervation dilates the iris, thus temporarily letting more light reach the retina.