Coordination and control – the nervous system — OCR GCSE Biology
Test yourself on Coordination and control – the nervous system with OCR GCSE practice questions.
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Coordination and control – the nervous system explained
Common optical defects arise when light fails to focus precisely on the retinal plane.
Read the full explanation
In myopia (short-sightedness), distant objects appear blurred because the eyeball is elongated or the lens is excessively curved, causing light rays to converge in front of the retina. This is corrected using concave (diverging) artificial lenses or laser corneal reshaping that flattens the cornea. In hyperopia (long-sightedness), close objects appear blurred because the eyeball is too short or the lens has lost elasticity with age, causing the focal point to fall behind the retina. Hyperopia is corrected using convex (converging) lenses that add refractive power. Colour blindness is an inherited condition caused by faulty or absent cone pigments in the retina.
Your focus
- Distinguish between the structural causes and focal defects of myopia and hyperopia.
- Explain how concave and convex lenses refract light to correct visual focusing defects.
- Describe the genetic basis and biological characteristics of human colour blindness.
Coordination and control – the nervous system exam tips
Marking Points
- explain myopia as the condition where rays focus in front of the retina due to an elongated eyeball or overly curved lens, corrected with concave lenses
- explain hyperopia as the condition where rays focus behind the retina due to a shortened eyeball or inflexible lens, corrected with convex lenses
- describe colour blindness as a genetic deficiency in red, green, or blue cone photoreceptors in the retina
- outline modern surgical treatments including laser corneal reshaping surgery and replacement intraocular lenses
Examiner Tips
- 💡Draw ray diagrams carefully: concave lenses diverge rays before entering the eye to push the focal point back onto the retina for myopia.
- 💡Remember that convex lenses converge rays before the cornea, bringing the focal point forward onto the retina to correct hyperopia.
Common Mistakes
- confusing the lens shapes used for correction, putting convex lenses on short-sighted eyes or concave lenses on long-sighted eyes
- assuming colour blindness can be cured with corrective spectacle lenses rather than managed with tinted filters
- stating that in long-sightedness light bounces off the retina instead of focusing behind the plane of the retina