Iris dilator muscle

Iris dilator muscle
Gray878.png
Iris, front view. (Muscle visible but not labeled.)
Gray883.png
The upper half of a sagittal section through the front of the eyeball. (Iris dilator muscle is NOT labeled and not to be confused with "Radiating fibers" labeled near center, which are part of the ciliary muscle.)
Latin musculus dilatator pupillae
Gray's subject #225 1013
Origin outer margins of iris[1]
Insertion    inner margins of iris[1]
Artery
Nerve Long ciliary nerves (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[2] of the eye, running radially in the iris and therefore fit as a dilator. It has its origin from the anterior epithelium.[3] It is innervated by the sympathetic system, which acts by releasing noradrenaline, which acts on α1-receptors.[4] Thus, when presented with a threatening stimuli that activates the fight-or-flight response, this innervation contracts the muscle and dilates the iris, thus temporarily letting more light reach the retina.

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Additional images

See also

References

  1. ^ a b Gest, Thomas R; Burkel, William E. "Anatomy Tables - Eye." Medical Gross Anatomy. 2000. University of Michigan Medical School. 5 Jan. 2010 <http://anatomy.med.umich.edu/nervous_system/eye_tables.html>.
  2. ^ jneurosci.org Muscarinic and Nicotinic Synaptic Activation of the Developing..
  3. ^ "eye, human." Encyclopædia Britannica. Encyclopaedia Britannica Ultimate Reference Suite. Chicago: Encyclopædia Britannica, 2010.
  4. ^ Rang, H. P. (2003). Pharmacology. Edinburgh: Churchill Livingstone. ISBN 0-443-07145-4.  Page 163

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Look at other dictionaries:

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