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Question
A student touches a sharp pin. Describe the reflex arc that causes their hand to pull away. (6 marks)
Solution
Identify the stimulus: the sharp pin.
Receptors (pain/touch receptors) in the skin detect the stimulus.
Sensory neurone carries the impulse to the spinal cord.
Relay neurone in the spinal cord passes it to the motor neurone.
Motor neurone carries the impulse to a muscle in the arm.
The muscle (effector) contracts, pulling the hand away.
Answer
Stimulus = pin (1). Receptors in skin detect it (1). Sensory neurone carries impulse to spinal cord (1). Relay neurone in spinal cord passes it to motor neurone (1). Motor neurone carries impulse to bicep muscle (1). Muscle (effector) contracts, pulling hand away (1).
Question
Describe how an electrical impulse is transmitted across a synapse from one neurone to the next. (3 marks)
Solution
The impulse arrives at the end of the first neurone, causing it to release chemical neurotransmitters into the synapse.
The neurotransmitters diffuse across the gap.
They bind to receptors on the next neurone, triggering a new electrical impulse in it.
Answer
When the impulse reaches the end of the first neurone, it releases chemical neurotransmitters into the synapse (1). The neurotransmitters diffuse across the gap (1) and bind to receptors on the second neurone, triggering a new electrical impulse in it (1).
Examiner note
Use the word 'diffuse' for movement across the synapse — examiners look for this term.
Question
Describe the method for measuring a person's reaction time using a ruler-drop test. Include any control variables. (6 marks)
Solution
Subject sits with arm on table, hand over edge, thumb and finger at 0 cm mark of ruler but NOT touching.
Partner holds the ruler vertically with 0 cm at the subject's fingers.
Partner drops the ruler WITHOUT warning; subject catches as fast as possible.
Read off the distance fallen (cm) and convert to time using a table or t = √(2s/g).
Repeat at least 3 times and calculate the mean.
Control variables: same hand, same height, same dropper, no warning, same person doing the dropping.
Answer
Subject's hand on a table edge with thumb and finger at the 0 cm mark (1). Partner holds the ruler vertically aligned (1). Partner drops without warning; subject catches (1). Distance caught is recorded and converted to time (1). Repeat 3+ times and take the mean (1). Control: same hand, same dropper, no warning, same starting height (1).
Question
Before drinking coffee, a student's mean ruler-drop distance was 22 cm (= 0.21 s). After drinking, mean was 16 cm (= 0.18 s). What does this suggest? (3 marks)
Solution
Compare numerically: drop fell from 0.21 s to 0.18 s, a decrease of 0.03 s (~14%).
A smaller reaction time means a FASTER response — caffeine speeded up the response.
However, the experiment used only one student. Without repeats on more people and statistical analysis, this is suggestive but not conclusive.
Answer
Reaction time decreased from 0.21 s to 0.18 s — a faster response (1). This suggests caffeine reduces reaction time / speeds up the response (1). The result is from one person only; more subjects and repeats would be needed to be confident the difference is significant and not random (1).
Examiner note
Always comment on sample size when evaluating reaction-time data — examiners credit this critically.
Question
Name the three main regions of the brain identified by AQA and give one function of each. (6 marks)
Solution
Cerebrum / cerebral cortex — consciousness, intelligence, memory, language.
Cerebellum — coordination of muscle movements and balance.
Medulla — controls unconscious activities (heart rate, breathing).
Answer
Cerebrum / cerebral cortex (1) — controls consciousness, intelligence, memory and language (1). Cerebellum (1) — controls balance and coordination of muscle movements (1). Medulla (1) — controls unconscious actions like heart rate and breathing (1).
Question
Evaluate why it is hard to treat disorders of the brain. (4 marks)
Solution
The brain is delicate — any surgery risks damaging healthy tissue.
The brain is very complex — functions overlap across regions, making surgery uncertain.
The blood-brain barrier stops most drugs from reaching brain tissue.
Damaged neurones do not regenerate — lost function may be permanent.
Answer
The brain is delicate, so surgery risks damaging healthy tissue (1). It is very complex with overlapping functions, so treatments can have unintended effects (1). The blood-brain barrier prevents many drugs from reaching brain tissue (1). Damaged neurones do not regenerate, so lost function may be permanent (1).
Examiner note
Two or more reasons must be given for full credit on an 'evaluate' question.
Question
Describe how the eye focuses on a near object. (4 marks)
Solution
The ciliary muscles contract.
The suspensory ligaments become slack/loose.
Tension on the lens is released, so the lens becomes thicker / more curved.
The fatter lens refracts (bends) the diverging light rays more strongly, focusing them on the retina.
Answer
Ciliary muscles contract (1). Suspensory ligaments become slack (1). The lens becomes fatter / more curved (1). The lens refracts light more strongly, focusing it on the retina (1).
Question
A student cannot see the board clearly from the back of the class. State the name of this defect and the type of lens used to correct it. (2 marks)
Solution
She can't see distant objects, so this is myopia (short sight).
Corrected with a concave (diverging) lens.
Answer
Myopia / short sight (1). Concave / diverging lens (1).
Question
A runner's body temperature rises during a hot summer race. Explain TWO ways the body responds to lower her body temperature back to normal. (4 marks)
Solution
Sweat glands produce sweat onto the skin surface.
Water in sweat evaporates, taking thermal energy from the skin — cooling the body.
Arterioles supplying skin capillaries undergo vasodilation (widen).
More warm blood flows close to the skin surface, so more heat is lost by radiation.
Answer
Sweat glands produce sweat (1); evaporation of water from sweat removes thermal energy and cools the body (1). Skin arterioles undergo vasodilation (1); more blood flows near the surface and more heat is lost by radiation (1).
Question
Describe two ways the body responds when it gets too cold. (4 marks)
Solution
Skeletal muscles contract rapidly (shivering).
These contractions need respiration, which releases heat — warming the body.
Vasoconstriction — skin arterioles narrow.
Less blood flows near the surface — less heat is lost.
Answer
Shivering — skeletal muscles contract (1); respiration in muscles releases heat to warm the body (1). Vasoconstriction — skin arterioles narrow (1); less blood flows near the skin so less heat is lost (1).
Distance-to-time conversion for a dropped object
When to use
When asked to convert ruler-drop distance to reaction time in the lab.
Example
If a ruler falls s = 0.20 m, then t = √(2 × 0.20 / 9.81) ≈ √0.0408 ≈ 0.20 s.
The brain and spinal cord; the coordination centre of the nervous system.
A specialised cell that carries electrical impulses through the nervous system.
The tiny gap between two neurones, across which signals are passed using chemical neurotransmitters.
An automatic, rapid response to a stimulus that does not involve the conscious brain; its purpose is to protect the body.
The pathway of a reflex: stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response.
The time taken between detecting a stimulus and producing a response (typically 0.20–0.25 s in healthy young adults).
A substance that increases nervous activity, generally reducing reaction time. Caffeine is the most common example.
A substance that slows nervous activity, generally increasing reaction time. Alcohol is the most common example.
Sum of all valid measurements divided by the number of measurements; used to reduce the effect of random variation between repeats.
The largest, outermost part of the brain. Responsible for consciousness, intelligence, memory and language.
The region at the lower back of the brain that controls balance and coordination of muscle movements.
Region of the brain stem that controls unconscious activities such as heart rate and breathing.
Magnetic Resonance Imaging — a non-invasive technique that uses magnetic fields and radio waves to produce detailed images of the brain (and other soft tissues).
A selective barrier of cells in the brain's blood vessels that prevents most substances (including most drugs) from passing from blood into brain tissue.
The transparent front layer of the eye that does most of the focusing by refracting light.
The coloured ring of muscle that controls the size of the pupil and so the amount of light entering the eye.
Transparent, flexible structure that fine-tunes the focusing of light onto the retina by changing shape (accommodation).
Light-sensitive layer at the back of the eye containing rods and cones — receptor cells that convert light into nerve impulses.
The process by which the eye changes the shape of the lens to focus light from near or far objects onto the retina.
A vision defect where distant objects appear blurry because light is focused in front of the retina. Corrected with a concave (diverging) lens.
A vision defect where near objects appear blurry because light is focused behind the retina. Corrected with a convex (converging) lens.
A region of the brain that monitors and controls body temperature. Contains receptors sensitive to the temperature of the blood and receives information from skin temperature receptors.
Widening of arterioles supplying skin capillaries so more warm blood flows near the surface and more heat is lost. Response to overheating.
Narrowing of arterioles supplying skin capillaries so less blood flows near the surface and less heat is lost. Response to being too cold.
Production of sweat by sweat glands. The evaporation of water in sweat removes thermal energy from the skin and cools the body.
Rapid involuntary contractions of skeletal muscles. Respiration in muscles releases heat to warm the body.
A control mechanism where a change in a condition triggers a response that brings the condition back towards the set point.
Mistake
Including the brain in the reflex arc pathway.
Why it happens
Assuming the brain is needed for any action.
How to avoid it
The relay neurone is in the SPINAL CORD. The conscious brain is bypassed.
Mistake
Saying motor neurones carry impulses to the CNS.
Why it happens
Confusing sensory and motor neurones.
How to avoid it
Sensory IN (to CNS); Motor OUT (from CNS to effector). Think 'sensory senses', 'motor moves'.
Mistake
Saying the electrical impulse jumps the synapse.
Why it happens
Not knowing that synapses are gaps.
How to avoid it
Impulse arrives → CHEMICAL neurotransmitters released → diffuse across → trigger new impulse on the other side.
Mistake
Forgetting 'without warning' in the method.
Why it happens
Skipping over the step.
How to avoid it
Without warning is essential — otherwise the subject anticipates and you're not measuring reaction.
Mistake
Reporting a single result.
Why it happens
Treating one go as good enough.
How to avoid it
Always repeat AT LEAST 3 times and take the mean. Random variation can be huge in single trials.
Mistake
Only listing one control variable.
Why it happens
Not thinking through the test.
How to avoid it
Name at least three: same hand, same dropper, same height, no warning. Each is a credit-bearing mark.
Mistake
Describing testing alcohol on students.
Why it happens
Misunderstanding ethics rules.
How to avoid it
GCSE classes can investigate caffeine. Alcohol is NOT tested directly — use secondary data instead.
Mistake
Swapping the functions of cerebellum and medulla.
Why it happens
Both names are unfamiliar.
How to avoid it
Cerebellum = COORDINATION (think 'sells-it-well' — needs balance). Medulla = MAINTAINS heart/breath.
Mistake
Calling the whole brain the 'cerebrum'.
Why it happens
Cerebrum looks like 'brain' on a diagram.
How to avoid it
Cerebrum is ONE PART — the wrinkled top. Cerebellum and medulla are separate.
Mistake
Giving only one reason on an 'evaluate' question.
Why it happens
Not realising 'evaluate' = multiple-mark.
How to avoid it
Always give two or more reasons (delicate, complex, blood-brain barrier, etc.).
Mistake
Saying suspensory ligaments tighten when ciliary muscles contract.
Why it happens
Students assume 'contracts → pulls tight'.
How to avoid it
The ciliary muscles form a RING. When the ring contracts, it gets SMALLER, releasing tension on the ligaments — they slacken.
Mistake
Recommending convex for short sight (or concave for long sight).
Why it happens
Confusing naming.
How to avoid it
Memorise pair: short sight = concave; long sight = convex. (S-C / L-V — share no letters!)
Mistake
Calling the pupil a muscle, or the iris a hole.
Why it happens
Both are at the front of the eye and look similar in shape.
How to avoid it
Iris = coloured MUSCLE (controls). Pupil = the BLACK HOLE in the middle (light passes through).
Mistake
Saying 'sweat cools the body' without mentioning evaporation.
Why it happens
Pupils know sweating cools but don't explain why.
How to avoid it
Always write: water in sweat evaporates, taking thermal energy from the skin.
Mistake
'Blood vessels move closer to the skin' for vasodilation.
Why it happens
Misreading diagrams that show widened vessels appearing bigger.
How to avoid it
Vessels don't move. They WIDEN (vasodilation) or NARROW (vasoconstriction).
Mistake
'Shivering burns fat to make heat.'
Why it happens
Confusion with metabolism.
How to avoid it
Shivering causes muscle contraction, which needs respiration, which releases heat.