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The iris is not innervated directly, however the iris sphincter muscle is affected by the sympathetic and parasympathetic nervous systems. Sympathetic stimulation causes pupil dilation while parasympathetic nervous system causes pupil constriction. The parasympathetic response is quicker because of the proximity of a parasympathetic ganglion (ciliary ganglion) to the eye. The sympathetic response is slower because all sympathetic ganglia are confined to the spinal cord. This is the reason why people adjust faster to a bright shining light than darkness.
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What are the intrinsic eye muscles controlled by?
The iris and the ciliary muscle
How does sympathetic nervous system affect the iris?
The sympathetic nervous system is one of three major parts of the autonomic system. The autonomic nervous system (ANS) is the part of the nervous system that controls most of the things we don't do voluntarily. Things such as heart rate, respiratory rate, sexual arousal and tone of the muscle inside your eye (the iris). The sympathetic part of the ANS is often considered to promote a "fight or flight response" while the parasympathetic part does the opposite ("rest and digest"). If we think about a dangerous situation where you want to have a "fight or flight response", you generally want to have more light entering your eyes so that you have a heightened visual sense. This is accomplished when your sympathetic nervous system activates the radial muscles of your iris. In contrast, your constricter muscles are relaxed. This leads to dilated pupils forming part of the sympathetic response.
What are the divisions of the ANS?
The division of the autonomic nervous system responsible for each of the reflexes is the ciliospinal reflex. Ciliospinal reflex responds mainly by the 2nd and 3rd order nerves to the muscle of the iris.
What system that allows the reading of patterns in the iris of the eye?
iris recognition
What part of the eye controls the amount of light passing into the eye?
The pupil constricts or dilates depending on how much light is available. The pupil's function is controlled by our autonomic nervous system.
Who invented the iris scanner?
John Daugman was the inventor of the iris recognition system.
Which system controls the rate at which you blink?
Iris muscles! The circular muscles contract to reduce the size of the pupil in bright light. Radial muscle fibres contract to widen the pupil in places of low light intensity. The contraction and relaxation of circular and radial muscle fibres in the iris are antagonistic, and an example of cerebral reflex.
What does an iris recognition system measure?
Because our irises are unique, some use iris recognition as a security device.
What is a iris scan?
Like fingerprints, a person's iris is unique. An iris scan is accomplished by a system that uses a device like a digital camera to record details about a person's iris. The image is converted to an iris code and stored in a database for future use.
How does closing the iris diaphragm affect image brightness and contrast?
An iris diaphragm controls the amount of light admitted to a lens. Closing the iris diaphragm will decrease the brightness and increase the contrast of an image.
What is accuracy rates of iris recognition system?
The false acceptance rate (misidentification rate) for iris recognition is 1 in 1.2 Million.
Can cataracts turn brown eyes blue in humans?
No, eye color is determined by the properties of the iris. Cataracts develop inside the lens, which is behind the iris. In very bad cases of cataracts the pupil can look cloudy or even white, but this does not affect the iris color.
