Iris (Definition) The iris is a structure within the eye that helps reduce the amount of light that reaches the retina. The iris is known as the colored part of the eye, and can be blue, brown, or any color or combination of colors in between. The iris is the portion of the eye that responds to light stimulation. ...Read more.
Scientists also speculate that caffeine may provide a mood-boosting effect that helps ease pain. Regardless of the mechanism by which it works, the data does indicate that caffeine does indeed make pain medications more effective and help ease pain.
Since caffeine narrows the blood vessels that surround your brain, when you stop taking it they expand again, and that can cause pain. Withdrawal: Itâs easy for your body to get so used to the effects of caffeine that when you donât have it in your system, you have withdrawal. A headache is one of the symptoms. This can happen when you have caffeine regularly, even as little as a cup of coffee a day.