The amount of light entering the eye is controlled by a reflex action. The size of the pupil changes in response to bright or dim light. This is controlled by the muscles of the iris.

Information from receptors passes along neurones, as electrical impulses to co-ordinators such as the central nervous system or CNS. The CNS is the brain and spinal cord. Muscles contracting or ...

We are at a critical time and supporting climate journalism is more important than ever. Science News and our parent organization, the Society for Science, need your help to strengthen ...