IGCSE Biology / Coordination

Bright light and dim light

Edexcel International GCSE Biology (4BI1), chapter 6: Coordination, specification point 2.92. Part of the full course.

Read the revision notes · IGCSE Biology past papers

The pupil reflex changes pupil size by making two sets of iris muscles contract or relax. This controls how much light enters the eye and helps protect the retina from very bright light.

More lessons in Coordination

• Central and peripheral nervous system
• Comparing nervous and hormonal control
• The three types of neurone, and the synapse
• The structure of the eye
• Focusing on near and distant objects
• Reflex actions