OCR GCSE Biology A: The eye, eye defects, the brain and limits of treatment (J247) – Revision Notes

These notes condense statements B3.1d to B3.1h of the OCR GCSE (9-1) Gateway Science Biology A (J247) specification, Version 4.0 (August 2026), for first assessment in 2018. For full explanations and worked examples, read the study guide. When you are ready, try the practice questions, tick off the checklist, see the OCR GCSE Biology hub and take a free diagnostic. Statements B3.1g and B3.1h are bold in the specification, so they are Higher Tier only.

The eye (B3.1d)

Part	Function in one line
Cornea	Transparent front; refracts light, does most of the focusing
Iris	Muscle; changes pupil size
Pupil	Opening that lets light through
Lens	Transparent and flexible; fine focusing onto the retina
Retina	Contains rods (dim light) and cones (colour); changes light into impulses
Optic nerve	Sends impulses from retina to brain
Ciliary body	Ring of muscle that alters lens shape
Suspensory ligaments	Fibres linking ciliary body and lens

Iris reflex in brief

Light	Circular muscles	Radial muscles	Pupil
Bright	Contract	Relax	Smaller
Dim	Relax	Contract	Larger

Accommodation (focusing)

	Near object	Distant object
Ciliary muscle	Shortens	Lengthens
Tension in ligaments	Low	High
Lens	Fatter	Slimmer
Light bent	More	Less

Memory line: near means shorten, loose, fat.

Eye defects (B3.1e)

Defect	What is seen	Cause	Focus falls	Correction
Short-sightedness	Near clear, far blurred	Eyeball too long or lens too strong	In front of retina	Concave (diverging) lens; laser reshaping of cornea
Long-sightedness	Far clearer, near blurred	Eyeball too short or lens too weak	Behind retina	Convex (converging) lens; laser surgery or lens replacement
Colour blindness	Some colours hard to tell apart	Inherited; faulty or missing cones	Not a focus problem	No cure; colour filters can help some people

Method in steps for any defect question:

1. Name the defect from the symptom (which distance is blurred).
2. Say where the focus falls compared with the retina.
3. Give the cause (eyeball length or lens power).
4. Name the lens that fixes it and say what it does to the light.

The brain (B3.1f)

Region	Function
Cerebrum	Conscious thought, memory, language, intelligence, sensory information, voluntary movement
Cerebellum	Coordination of movement, balance
Medulla	Unconscious actions: breathing rate, heart rate
Hypothalamus	Monitors and controls body temperature and water balance
Pituitary	Releases hormones, many of which control other glands (“master gland”)

Distinction to know: the cerebrum controls actions you choose to do; the medulla controls those you do not have to think about.

Investigating the brain (B3.1g, Higher Tier only)

Difficulty	Point to make
Access	Soft, delicate, inside the skull; cannot be inspected safely when working
Case studies	Rare, each injury differs, small sample, no information about before the injury
Interpreting	Other areas may compensate; one area active does not prove it is the cause
Ethics	Consent from patients, confidentiality, no deliberate harm, animal welfare and differences

Treating damage (B3.1h, Higher Tier only)

Limitation	Point to make
Limited repair	Damaged neurones in the brain and spinal cord are not readily replaced
Surrounding tissue	Surgery or radiation can irreversibly harm healthy tissue
Access	Skull and backbone protect the system, so deep parts are hard and risky to reach

Treatments often reduce symptoms without replacing lost neurones.

Worked reminders

Pupil data. Diameter falls from 6.0 mm to 3.0 mm. Percentage decrease = (6.0 − 3.0) ÷ 6.0 × 100 = 50%. Area scales with diameter squared, so the opening is 4 times smaller (area ratio 28.3 mm² to 7.07 mm²).

Diagnose the region. A person speaks and remembers normally but cannot keep their balance: cerebellum.

Explain a limitation. “Neurones in the spinal cord do not readily regrow [1], so a broken pathway stays broken [1].”

Must-know distinctions

• Rods and cones. Rods work in dim light and do not give colour. Cones need brighter light and give colour vision. Colour blindness involves the cones.
• Cornea and lens. Both refract light. The cornea has a fixed shape and does most of the bending. The lens can change shape, so it makes the adjustment for near and far.
• Iris and pupil. The iris is the muscle. The pupil is the gap it surrounds.
• Short-sight and long-sight. Short-sight: far objects blurred, concave lens, image forms before the retina. Long-sight: near objects blurred, convex lens, image would form beyond the retina.
• Medulla and cerebrum. The medulla runs unconscious, life-supporting actions. The cerebrum handles conscious thought and voluntary actions.
• Hypothalamus and pituitary. The hypothalamus monitors conditions and controls the pituitary. The pituitary releases hormones into the blood.
• Symptom relief and repair. Many nervous system treatments relieve symptoms. Repair means replacing lost nerve tissue, which is currently very limited.

Method for data questions

The specification lists extracting and interpreting data from graphs, charts and tables.

1. Read the title and the units on each axis or column before anything else.
2. Describe the trend in words, quoting at least two values from the data with their units.
3. Calculate where asked. A percentage change is (new − old) ÷ old × 100.
4. Explain using biology: name the structure, say what it does, and link it to the data.
5. Comment on reliability if asked: sample size, spread of results, whether other factors were controlled.

Model answers to extended questions

Explain how the eye adjusts when you look from a distant tree to a book. The ciliary muscle contracts [1]. This slackens the suspensory ligaments [1]. The lens is no longer pulled flat, so it becomes thicker and more curved [1]. Light is refracted more [1], so the image from the near object is focused on the retina [1].

Explain why a person is short-sighted, and how glasses help. The eyeball is too long, or the lens is too strong [1]. The focus for distant objects forms before the retina [1], so what lands on the retina is blurred [1]. A concave lens spreads the light slightly before it enters the eye [1]. The focus then moves back onto the retina [1].

Discuss why brain function is difficult to investigate (Higher Tier only). The brain is delicate and protected inside the skull, so it cannot be examined safely while working [1]. Case studies depend on rare injuries that are all different [1], and the sample is small, so results are hard to generalise [1]. Damage to one area may be made up for by others, which makes the cause of a symptom uncertain [1]. Ethically, patients may not be able to consent, and deliberate harm to humans or animals is not acceptable [1].

Explain why a brain tumour can be hard to treat (Higher Tier only). The tumour may be deep, and reaching it through the skull is risky [1]. Removing it, or treating it with radiation, may damage healthy nervous tissue around it [1]. Neurones do not readily regrow, so that damage may be permanent [1].

Quick self-test

1. Which part of the eye contains the light receptors?
2. What do the circular muscles of the iris do in bright light?
3. State the state of the ciliary muscle and suspensory ligaments when you look at a distant object.
4. Why is the image blurred for a short-sighted person looking at a distant tree?
5. Which type of lens corrects long-sightedness?
6. Why can colour filters not cure colour blindness?
7. Which region of the brain is mainly responsible for balance?
8. Name the region that monitors body temperature.
9. (Higher Tier only) Give two reasons why a single case study of a brain-injured patient is hard to interpret.
10. (Higher Tier only) Give one reason why neurosurgery may cause irreversible damage.
11. A pupil has diameter 8.0 mm in dim light and 2.0 mm in bright light. Calculate the percentage decrease in diameter.
12. State the function of the suspensory ligaments.

Answers

1. The retina (rods and cones).
2. They contract, making the pupil smaller.
3. Ciliary muscle relaxed, suspensory ligaments taut (so the lens is thin).
4. The eyeball is too long or the lens too strong, so the focus forms before the retina.
5. A convex (converging) lens.
6. They only help the person tell colours apart; the faulty cone cells are still not working.
7. The cerebellum.
8. The hypothalamus.
9. For example: it is a very small sample, and no two injuries are the same; the person’s abilities before the injury are usually not known.
10. The surgeon may need to cut through, or may damage, healthy tissue near the target, and this nervous tissue cannot be replaced.
11. (8.0 − 2.0) ÷ 8.0 × 100 = 75%.
12. They connect the ciliary body to the lens and pass on the pull that changes the lens shape.

Where marks are usually lost

• Writing “the iris lets in light” instead of “the pupil lets in light; the iris controls its size”.
• Saying the ligaments contract or relax. Name the ciliary muscle for that.
• Giving the wrong lens for a defect, or not saying where the image forms.
• Describing long-sight as caused by a long eyeball.
• Calling colour blindness “curable” or saying that rods are faulty.
• Giving only “thinking” for the cerebrum or only “movement” for the cerebellum; add coordination and balance.
• Writing “it is dangerous” for B3.1g without saying why a brain study is hard.
• Forgetting to give a calculated percentage change as a positive value with the word “decrease” or “increase”.
• Saying every neurone can never be repaired. Say repair is limited.

Official syllabus

OCR, GCSE (9-1) Gateway Science Biology A (J247), Version 4.0 (August 2026), for first assessment in 2018: statements B3.1d to B3.1h.