Iris dilator muscle
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| 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 | |
| Origin: | ||
| Insertion: | ||
| Blood: | ||
| 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
Contents |
[edit] Additional images
 Sympathetic connections of the ciliary and superior cervical ganglia. |
[edit] See also
[edit] References
- ↑ jneurosci.org Muscarinic and Nicotinic Synaptic Activation of the Developing..
- ↑ Rang, H. P. (2003). Pharmacology, Edinburgh: Churchill Livingstone. Page 163
[edit] External links
- Description of function at tedmontgomery.com
- Slide at mscd.edu
- Dictionary at eMedicine dilator+pupillae+muscle
- Histology at Boston University 08010loa
scalp/eyelid: occipitofrontalis (occipitalis, frontalis) - orbicularis oculi - corrugator supercilii - depressor supercilii
extraocular: levator palpebrae superioris - superior tarsal - rectus (superior, inferior, medial, lateral) - oblique (superior, inferior) - intraocular: ciliary - iris dilator - iris sphincter
ear: auriculares - temporoparietalis - stapedius - tensor tympani
nose: procerus - nasalis (dilatator naris) - depressor septi nasi - levator labii superioris alaeque nasi
mouth: levator anguli oris/depressor anguli oris - levator labii superioris/depressor labii inferioris - zygomaticus (major, minor) - mentalis - buccinator - orbicularis oris - risorius
mastication: masseter - temporalis - pterygoid (lateral, medial)
tongue: extrinsic (genioglossus - hyoglossus - chondroglossus - styloglossus) intrinsic (superior longitudinal - inferior longitudinal - transversus - verticalis)
soft palate: levator veli palatini - tensor veli palatini - musculus uvulae - palatoglossus - palatopharyngeus
pharynx: pharyngeal constrictor (inferior, middle, superior) - stylopharyngeus - salpingopharyngeus
larynx: cricothyroid - posterior cricoarytenoid - lateral cricoarytenoid - arytenoid - thyroarytenoid
| This page uses content from the English-language version of Wikipedia. The original article was at Iris dilator muscle. The list of authors can be seen in the page history. As with Psychology Wiki, the text of Wikipedia is available under the GNU Free Documentation License. |
