Biology · Growth and Development

The retina is a thin layer of tissue that lines the back of the eye on the inside. It is located near the optic nerve. The purpose of the retina is to receive light that the lens has focused, convert the light into neural signals, and send these signals to the brain for visual recognition.

The main function of the retina is to receive light that the lens has focused, convert the light into neural signals and send these signals to the brain for visual recognition.

Metabolism is the chemical reactions in the body's cells that change food into energy. Our bodies need this energy to do everything from moving to thinking to growing. Specific proteins in the body control the chemical reactions of metabolism.

Muscle contraction is the activation of tension-generating sites within muscle cells. 

Muscle twitches are caused by our muscles tightening up "contracting"involuntarily. Muscle twitches can happen for lots of reasons, like stress, too much caffeine, a poor diet, exercise, or as a side effect of some medicines.