Sphincter Muscle

... center of the iris is called the pupil. The iris is embedded with tiny muscles that dilate (widen) and constrict (narrow) the pupil size. The sphincter muscle lies around the very edge of the pupil. In bright light, the sphincter contracts, ...

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... controlled by autonom nerve which is: Symphatetic for irises' dilator muscle to open the pupils wider. Parasymphatetic for irises' sphincter muscle to make the pupils more narrow. For the oculomotoric, throclear and abdusen ...

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The contraction and relaxation of iris generated by pupilary sphincter muscle after stimulated by light. That muscle in innervated by nerve III. If the blindness is caused ...

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