| Iris dilator muscle | |
|---|---|
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| Iris, front view. (Muscle visible but not labeled.) | |
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| 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 |
| Origin | |
| Insertion | |
| Artery | |
| Nerve | superior cervical ganglion (sympathetics) |
| Actions | dilates pupil |
| Antagonist | iris sphincter muscle |
The iris dilator muscle (pupil dilator muscle, pupillary dilator, radial muscle of iris, radiating fibers), is a smooth muscle[1] of the eye, running radially in the iris and therefore fit as a dilator. It is innervated by the sympathetic system, which acts by releasing noradrenaline, which acts on α1-receptors.[2]. 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.
Contents |
Additional images
 Sympathetic connections of the ciliary and superior cervical ganglia. |
 The iris dilator muscle is concentric with the pupil. |
See also
References
- ^ jneurosci.org Muscarinic and Nicotinic Synaptic Activation of the Developing..
- ^ Rang, H. P. (2003). Pharmacology. Edinburgh: Churchill Livingstone. ISBN 0-443-07145-4. Page 163
External links
- Description of function at tedmontgomery.com
- Slide at mscd.edu
- dilator+pupillae+muscle at eMedicine Dictionary
- Histology at BU 08010loa
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