8.6.1 Brain chemicals in Parkinson's and depression Quiz: Pearson Edexcel Biology A (Salters-Nuffield), Unit 8

The 20 questions

1. Which neurotransmitter is deficient in Parkinson's disease?

   • Glutamate in the cerebellum only, which is lost from the cerebellar cortex as the disease progresses
   • Dopamine, whose loss from the substantia nigra underlies the movement symptoms of Parkinson's disease
   • Acetylcholine at all synapses, which is depleted throughout the brain and the spinal cord in the disease
   • Serotonin only, which is the main chemical deficient in Parkinson's and is replaced by dopamine therapy

2. Which neurotransmitter is most closely linked to the low-mood hypothesis of depression?

   • Adrenaline only, which is released at low levels in people with depression and affects mood directly
   • Insulin, which is linked to depression because low insulin levels in the brain reduce the motivation to act
   • Oxytocin only, which is the hormone that is consistently reduced in every form of depression in the body
   • Serotonin, since reduced serotonin activity in the brain is proposed to contribute to depression

3. Which region of the brain contains the neurones that are lost in Parkinson's disease?

   • Cerebellum, which co-ordinates movement and is the main site of dopamine loss in the disease
   • Corpus callosum, which connects the two hemispheres and is where most of the lost neurones are found
   • Medulla oblongata, which controls breathing and heart rate and is damaged in the early stages of the disease
   • Substantia nigra, where dopamine-producing neurones degenerate, reducing dopamine supply to the striatum

4. Which symptom is characteristic of Parkinson's disease?

   • Loss of hearing in both ears, which is caused by damage to the auditory nerve in the brainstem
   • Tremor and rigidity of muscles, along with slowed movement, caused by a deficiency of dopamine
   • Increased appetite only, which is caused by excess dopamine and leads to rapid weight gain
   • Excess production of insulin, which causes a sharp fall in blood glucose and loss of consciousness

5. Why is L-Dopa used to treat Parkinson's disease?

   • It kills the substantia nigra to stop tremors, by removing the source of the abnormal electrical activity
   • It blocks all synapses in the brain, which stops the uncontrolled movements that the disease causes
   • It is converted into dopamine in the brain, replacing the lost neurotransmitter and easing the symptoms
   • It increases the production of insulin, which lowers the level of dopamine released in the brain

6. Why does L-Dopa, rather than dopamine itself, get used as a treatment?

   • Dopamine is always toxic to neurones, so it can never be used as a medicine in any form or dose
   • L-Dopa is more expensive, so it is preferred by doctors even though it has the same effect as dopamine
   • Dopamine is found only in the liver, so it cannot reach the brain from the blood in any amount
   • Dopamine cannot cross the blood-brain barrier, but L-Dopa can, and is then converted into dopamine in the brain

7. Which statement describes a limitation of L-Dopa treatment for Parkinson's disease?

   • It treats symptoms but does not stop the progressive loss of neurones, so its effect declines over time
   • It has no effect on movement, since it only changes the mood of patients with Parkinson's disease
   • It cures the disease permanently, so patients do not need to take it once they have started the treatment
   • It prevents all tremor in every patient, which means that no further monitoring is needed during treatment

8. A patient with depression has low serotonin activity in synapses. Which drug type could help by increasing serotonin in the synapse?

   • Anticoagulant that thins the blood, which reduces clotting and is used to treat clots in the veins
   • Anti-diabetic drug that raises insulin, which lowers blood glucose but has no direct effect on serotonin
   • Selective serotonin reuptake inhibitor (SSRI), which blocks reuptake so that more serotonin remains in the cleft
   • Dopamine agonist that blocks serotonin, which reduces the serotonin signal and so worsens the symptoms

9. Why might a drug that blocks serotonin reuptake raise serotonin activity?

   • It increases the number of myelin sheaths on the serotonin neurones, which speeds up the impulses
   • Serotonin stays in the cleft for longer, increasing the stimulation of postsynaptic receptors
   • It prevents serotonin from being released, which causes it to accumulate inside the presynaptic neurone
   • Serotonin is converted to insulin, which is then released into the blood and lowers the blood glucose level

10. Which statement best describes the chemical basis of Parkinson's disease?

    • Deficiency of red blood cells, which reduces the oxygen supply to the brain and damages the motor pathways
    • Imbalance or loss of dopamine due to degeneration of dopamine-producing neurones
    • Blockage of the optic nerve, which prevents the visual signals from reaching the regions that control movement
    • Excess serotonin in the cerebellum, which blocks the movement signals sent by the motor cortex

11. A student says that depression is caused only by low serotonin. Which evaluation is most appropriate?

    • Correct, because serotonin is the only brain chemical involved, so every form of depression has the same cause
    • Incorrect, because serotonin has no effect on the brain, so it cannot contribute to depression in any way
    • Overstated, because depression is multi-factorial, and serotonin is one of several factors that may contribute
    • Correct, because serotonin is a hormone secreted by the thyroid, which is the main cause of all mood disorders

12. Which of the following is a function of dopamine in the brain?

    • Control of blood glucose in the liver only, since dopamine acts as a hormone in the liver's metabolism
    • Control of voluntary movement and reward pathways, with its loss underlying the motor symptoms of Parkinson's
    • Production of red blood cells in the bone marrow, which dopamine stimulates through the blood circulation
    • Breakdown of myelin in the axons of the peripheral nerves, which is the main role of dopamine in the body

13. Which of these best explains why SSRIs take several weeks to show benefits in depression?

    • The patient's kidneys must regrow before the drug can be processed, which takes a long period of treatment
    • SSRIs take effect immediately, so the delay is a mistake in the way the drug is prescribed to patients
    • Changes in receptor sensitivity and neural adaptation take time, not just the immediate rise in serotonin
    • The drug must be stored in the myelin sheath before it can act, which takes several weeks in every patient

14. A researcher measures dopamine levels in post-mortem tissue from people with Parkinson's disease and healthy controls. What result would support the dopamine hypothesis?

    • Dopamine levels are identical in both groups, which would show that dopamine is not involved in the disease
    • Dopamine levels are lower in the substantia nigra of Parkinson's patients than in healthy controls
    • Dopamine levels are higher in Parkinson's patients, which would show that dopamine causes the disease
    • Dopamine is absent in healthy controls only, which would show that the disease is caused by excess dopamine

15. Which statement best describes the role of serotonin in mood regulation?

    • It is a hormone that is produced only in muscle, where it controls the mood of the individual
    • It is a neurotransmitter that influences mood and behaviour through receptors in the brain
    • It is a structural protein in bones, which affects mood by changing the strength of the skeleton
    • It is an enzyme that digests glucose, which changes the mood by altering the energy supply to the brain

16. A drug is designed to block dopamine receptors and is found to worsen tremor in Parkinson's patients. Which explanation is most consistent?

    • Blocking receptors reduces dopamine signalling further in an already dopamine-deficient system
    • Blocking receptors increases dopamine production in the substantia nigra, which then causes the tremor
    • The drug has no effect on receptors, so the tremor must come from an unrelated cause in the patient
    • Blocking dopamine receptors cures Parkinson's, so the worsening tremor must be a rare side effect of recovery

17. A patient with Parkinson's disease responds well to L-Dopa at first but later develops involuntary movements. Which evaluation is most reasonable?

    • Long-term L-Dopa can cause side effects, so dose and monitoring must be balanced against symptom control
    • L-Dopa has no effect on dopamine levels in any patient, so the movements must be caused by another drug
    • Involuntary movements prove the disease has been cured, since the drug has restored normal dopamine signalling
    • The L-Dopa is useless and should be stopped immediately with no further assessment of the patient's condition

18. Which of these is a correct link between brain chemicals and disease?

    • Imbalance of naturally occurring brain chemicals can contribute to ill health, such as dopamine in Parkinson's
    • Brain chemicals cannot be linked to any disease, since they are only used for normal communication between cells
    • Only hormones from the pituitary cause brain disease, which is why brain chemicals are never involved in illness
    • Parkinson's is caused by a bacterial infection of the spinal cord only, with no role for any brain chemical

19. Which pair correctly matches a condition with its chemical imbalance?

    • Depression: insulin deficiency, which lowers the level of serotonin in the brain and causes low mood
    • Parkinson's disease: dopamine deficiency, caused by loss of dopamine-producing neurones
    • Depression: dopamine excess only, which is the main chemical imbalance seen in people with low mood
    • Parkinson's disease: serotonin excess only, which causes the tremor and the rigidity of the muscles

20. A student estimates that dopamine neurone loss in Parkinson's disease is 60 per cent. If a patient originally had 1000 units of dopamine-producing activity, how many units remain?

    • 40 units, found by taking 4 per cent of the original 1000 units that remain in the substantia nigra
    • 600 units, which is the amount lost, found by taking 60 per cent of the original 1000 units
    • 400 units, found by taking 40 per cent of the original 1000 units that remain after the loss
    • 160 units, found by taking 16 per cent of the original 1000 units after the loss of the neurones

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