5.6 Investigating and treating the brain
6 exam questions worth 19 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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Describe two methods scientists have used to find out which parts of the brain control particular functions.
Mark scheme
Two methods, each with a description (max 2 per method):
- studying patients with brain damage (1): link the damaged area to the function that is lost (1)
- electrical stimulation (1): a weak current / electrode applied to an area and the response observed / reported by the patient (1)
- MRI / fMRI (1): shows which areas are active / have more blood flow during a task (1)
- PET (1): radioactive tracer shows active areas (1)
- CT (1): X-rays show structure / location of damage (1)
Model answer
Scientists study patients with damage to one area of the brain: if the patient loses a particular function, that area is linked to it. They also use fMRI scans, which show the areas with increased blood flow while a person carries out a task, so those areas must be active in that task.
Compare how CT scans and PET scans are used to investigate the brain.
Mark scheme
- CT uses X-rays (from many angles) (1)
- PET uses a radioactive tracer (injected into the blood) (1)
- CT shows structure / damage / tumours (1)
- PET shows activity / which areas are most active (1)
- both use ionising radiation / both give images of slices / both are non-invasive (no surgery) (1)
Max 4
Model answer
Both scans produce images without surgery, but both use ionising radiation. A CT scan uses X-rays from many angles to show the structure of the brain, such as a tumour or bleeding. A PET scan uses an injected radioactive tracer; the most active areas take up the most tracer, so it shows brain activity rather than just structure.
Explain why a person with a badly damaged spinal cord may be permanently paralysed.
Mark scheme
- impulses cannot pass along / through the damaged part (1)
- so impulses cannot reach / travel from the brain to muscles (below the injury) (1)
- neurones (in the CNS) cannot regrow / repair (so it is permanent) (1)
Model answer
Impulses can no longer pass along the damaged part of the spinal cord, so impulses from the brain cannot reach the muscles below the injury. Neurones in the CNS can hardly repair themselves, so the damage is permanent.
Give two reasons why it is difficult to study how the brain works.
Mark scheme
Any two from:
- the brain is very complex / many interconnected neurones (1)
- one function may involve several areas (1)
- the brain is delicate / protected by the skull / hard to access (1)
- case studies are rare / each is different / hard to interpret (1)
- ethical issues / cannot experiment on healthy brains / consent (1)
Model answer
The brain is extremely complex, with many functions involving several areas, and there are ethical problems: scientists cannot damage healthy brains to test ideas.
A patient has a tumour deep inside the brain. Doctors suggest surgery to remove it.
Evaluate the use of surgery to treat the tumour.
Mark scheme
- benefit: removes the tumour / stops it growing or spreading / may save life (1)
- benefit: may relieve symptoms (e.g. headaches, seizures) (1)
- risk: healthy brain tissue may be damaged and cannot be replaced (1)
- risk: may lose functions such as speech / movement / memory (1)
- risk: tumour is deep / hard to access / may not remove it all (1)
- risk: infection / bleeding (1)
- conclusion weighing benefits against risks (1)
Max 4; for full marks there must be a benefit, a risk and a judgement
Model answer
Surgery could remove the tumour and stop it growing, which may save the patient's life and relieve symptoms. However, the tumour is deep, so the surgeon must cut through healthy brain tissue to reach it; neurones cannot regrow, so the patient might permanently lose abilities such as speech or movement, and there is a risk of infection. Surgery is worth it if the tumour is life-threatening and the area around it does not control vital functions; otherwise other treatments may be safer.
Suggest why electrical stimulation of the brain is usually done while the patient is awake.
Mark scheme
- the patient can report / describe what they feel / see / remember (1)
- the brain has no pain receptors so it does not hurt / allow: so the surgeon can see which area controls which function (1)
Model answer
The patient can tell the surgeon what they feel or see when each area is stimulated, and it is not painful because the brain has no pain receptors.
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