News tagged with eye

Related topics: brain · nerve cells · current biology · retina

Why do onions make you cry?

According to the National Onion Association (yes, that's a thing), approximately 170 countries grow onions, and it's estimated that 9.2 million acres of onions are harvested annually around the world. Onions are low in calories ...

Jun 26, 2017
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Choosing the right sunglasses

(HealthDay)—You might think of eye problems like cataracts as signs of old age, but one step you can take now will protect your vision for the future—and you can do it with style.

Jun 23, 2017
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Eye

Eyes are organs that detect light, and send signals along the optic nerve to the visual and other areas of the brain[citation needed]. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in cnidaria, molluscs, chordates, annelids and arthropods.

The simplest "eyes", such as those in unicellular organisms, do nothing but detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms. From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment.

This text uses material from Wikipedia, licensed under CC BY-SA

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