Psychology Wiki

Assessment | Biopsychology | Comparative | Cognitive | Developmental | Language | Individual differences | Personality | Philosophy | Social |
Methods | Statistics | Clinical | Educational | Industrial | Professional items | World psychology |

Biological: Behavioural genetics · Evolutionary psychology · Neuroanatomy · Neurochemistry · Neuroendocrinology · Neuroscience · Psychoneuroimmunology · Physiological Psychology · Psychopharmacology (Index, Outline)

Iris dilator muscle
Iris, front view. (Muscle visible but not labeled.)
The upper half of a sagittal section through the front of the eyeball. ("Radiating fibers" labeled near center.)
Latin musculus dilatator pupillae
Gray's subject #225 1013
Nerve: superior cervical ganglion (sympathetics)
Action: dilates pupil
Antagonist: iris sphincter muscle
Dorlands/Elsevier m_22/12548821

The iris dilator muscle (pupil dilator muscle, pupillary dilator, radial muscle of iris, radiating fibers), is a smooth muscle[1] of the eye. It is innervated by the sympathetic system, which acts by releasing noradrenaline, which acts on α1-receptors.[2]. Thus, when presented with a threating stimuli that activates the fight-or-flight response, this innervation dilates the iris, thus temporarily letting more light reach the retina.

It has the opposite effect to the iris sphincter muscle

Additional images

See also


  1. Muscarinic and Nicotinic Synaptic Activation of the Developing..
  2. Rang, H. P. (2003). Pharmacology, Edinburgh: Churchill Livingstone. Page 163

External links

This page uses Creative Commons Licensed content from Wikipedia (view authors).