This deep dive covers Eye Structure within Nervous System for GCSE Biology. Topic 2: Nervous System It is section 7 of 18 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
👁️ Eye Structure
The eye is a sense organ that contains receptors sensitive to light. Light enters the eye and is focused onto the retina, where receptor cells generate electrical impulses that travel along the optic nerve to the brain.
Parts of the eye and their functions:
| Part | What It Does |
|---|---|
| Cornea | Transparent front layer that refracts (bends) most of the light entering the eye |
| Iris | The coloured part of the eye; made of muscle that controls the size of the pupil |
| Pupil | The hole in the centre of the iris that lets light through; gets bigger in dim light, smaller in bright light |
| Lens | Fine-focuses light onto the retina; changes shape to focus on near or distant objects |
| Ciliary muscles | Ring of muscle around the lens that contracts or relaxes to change the lens shape |
| Suspensory ligaments | Fibres connecting ciliary muscles to lens; pull the lens thin when taut, allow it to bulge when slack |
| Retina | Light-sensitive layer containing rods (dim light, black/white) and cones (bright light, colour) |
| Optic nerve | Carries electrical impulses from the retina to the brain |
Key point: The cornea does most of the refraction, but the lens does the fine-focusing by changing shape. This process is called accommodation.
Practice questions for Nervous System
What are the two organs that make up the central nervous system (CNS)?
Explain how a signal is transmitted across a synapse from one neurone to the next.