8.6.2 Drugs acting on synaptic transmission Quiz: Pearson Edexcel Biology A (Salters-Nuffield), Unit 8

The 20 questions

1. What is an agonist drug at a synapse?

   • A drug that stops calcium entering the presynaptic knob only, so that no vesicles fuse with the membrane
   • A drug that digests the myelin sheath, which removes the insulation from the axon and slows impulses
   • A drug that blocks the receptor so the neurotransmitter cannot bind and produce any response
   • A drug that binds to the receptor and mimics the effect of the natural neurotransmitter

2. What is an antagonist drug at a synapse?

   • A drug that increases the release of dopamine only, which raises the level of the neurotransmitter in the cleft
   • A drug that converts L-Dopa into dopamine, which increases the amount of neurotransmitter in the brain
   • A drug that is a copy of acetylcholine, which activates the receptor just as the natural transmitter does
   • A drug that binds the receptor and prevents the natural neurotransmitter from binding and acting

3. How does a reuptake inhibitor affect synaptic transmission?

   • It increases the speed of the action potential, which shortens the time that neurotransmitter spends in the cleft
   • It stops neurotransmitter being taken back into the presynaptic neurone, so it stays in the cleft longer
   • It stops neurotransmitter from being released into the cleft, which removes the signal before it is sent
   • It breaks down the receptor on the postsynaptic membrane, which prevents the neurotransmitter from binding

4. How does an acetylcholinesterase inhibitor affect synaptic transmission?

   • It makes acetylcholine bind to dopamine receptors, which switches the signal to a different pathway in the brain
   • It prevents acetylcholine from being released, so the postsynaptic neurone receives no signal at all
   • It prevents sodium channels from opening, which stops the postsynaptic membrane from depolarising
   • It stops acetylcholine being broken down, so it stays in the cleft and stimulates the postsynaptic membrane for longer

5. Which drug acts on synapses by increasing the release of serotonin and blocking its reuptake?

   • Insulin, a hormone which lowers blood glucose by promoting the uptake of glucose into cells
   • Penicillin, an antibiotic which kills bacteria by stopping the synthesis of their cell walls
   • MDMA (Ecstasy), which increases serotonin release and blocks the serotonin transporter
   • Paracetamol, a pain reliever which acts mainly by reducing the production of prostaglandins

6. How does L-Dopa act to help people with Parkinson's disease?

   • It blocks dopamine receptors, which reduces the overactive signalling that causes the tremor
   • It is converted to dopamine, increasing the dopamine available to act on postsynaptic receptors
   • It destroys the substantia nigra to stop tremor, which removes the source of the abnormal electrical activity
   • It stops all neurotransmitters from being released, which quietens the uncontrolled activity of the brain

7. A drug is found to block the postsynaptic receptor for acetylcholine. What would be expected at a neuromuscular junction?

   • Calcium channels in the axon open continuously, which keeps the motor neurone firing at a high rate
   • Muscle contraction is reduced or prevented, because the signal cannot be transmitted to the muscle fibre
   • Acetylcholine release is increased, since the blocked receptors cause the motor neurone to release more of the transmitter
   • Muscle contraction is increased, because the blocked receptors allow more acetylcholine to reach the fibre

8. Which feature of a synaptic drug determines whether it acts as an agonist or an antagonist?

   • Its storage temperature, which affects whether the drug remains in its active form when it reaches the cleft
   • Its molecular weight alone, since heavier molecules always act as agonists and lighter ones always act as antagonists
   • Its colour, which determines whether the drug binds to the receptor or passes straight through the synapse
   • Its ability to change the shape of the receptor in a way that activates or blocks it

9. What is the expected effect of a drug that increases the amount of neurotransmitter released from a presynaptic neurone?

   • No change to the postsynaptic membrane, since the number of receptors limits the response and not the amount released
   • Increased myelin formation on the postsynaptic neurone, which is caused by a rise in neurotransmitter levels
   • Increased postsynaptic stimulation, if the receptors are available to bind the extra neurotransmitter
   • Decreased postsynaptic response, since more neurotransmitter causes the receptors to become less sensitive

10. A patient takes an antagonist drug for a condition involving excess acetylcholine action. Which effect would be expected?

    • Increased stimulation of the postsynaptic neurone, since the antagonist makes the receptor more sensitive
    • Increased release of acetylcholine, since the antagonist causes the presynaptic neurone to release more transmitter
    • Reduced stimulation of the postsynaptic neurone, since the antagonist blocks the receptor from binding acetylcholine
    • Fewer receptors on the postsynaptic membrane permanently, since the antagonist destroys the receptor protein

11. Which drug would most likely cause an increase in heart rate by acting on synaptic transmission?

    • A reuptake inhibitor for acetylcholine only, which slows the heart by keeping acetylcholine in the cleft longer
    • An agonist for adrenergic receptors that mimics adrenaline, which stimulates the receptors that speed up the heart
    • A drug that prevents calcium entry into the nucleus, which blocks the release of neurotransmitter at the heart
    • An antagonist for serotonin receptors only, which blocks the receptors that control the rate of the heart beat

12. A researcher finds a drug increases dopamine activity by blocking its reuptake. Which statement is correct?

    • Dopamine is converted into acetylcholine, which changes the type of signal sent to the postsynaptic cell
    • Dopamine stays in the synaptic cleft for longer, increasing postsynaptic stimulation
    • Dopamine can no longer be released, since the drug blocks the vesicles that carry it to the membrane
    • Dopamine is destroyed in the cleft, which reduces the amount of neurotransmitter that can act on the receptors

13. Why might an agonist that is not broken down cause a stronger or longer-lasting effect than the natural neurotransmitter?

    • It stays bound to receptors for longer, because it is not removed by enzymes or reuptake
    • It makes the myelin thicker, which increases the insulation and so prolongs the signal along the axon
    • It stops calcium from entering the knob, which means the receptor stays open for longer after each impulse
    • It is more quickly converted into hormones, which are then released into the blood and act on other organs

14. A student compares the effects of an SSRI and MDMA on serotonin. Which statement is the best comparison?

    • Both decrease serotonin activity, since each drug acts by blocking the serotonin receptors in the brain
    • Neither drug has any effect on serotonin, since both act only on dopamine receptors in the brain
    • SSRIs increase release and MDMA blocks receptors, which is the opposite of what the two drugs do
    • Both increase serotonin activity, but MDMA also increases serotonin release

15. Which statement describes a risk of using drugs that raise serotonin activity?

    • They increase the number of neurones permanently, which can lead to excess tissue in the brain
    • They always produce no side effects, since serotonin is a natural chemical that the body already makes
    • They can cause side effects by affecting many synapses, and misuse can cause serious harm
    • They cannot affect the heart, since serotonin acts only on the neurones of the brain and spinal cord

16. Which statement best describes a neuromuscular blocking drug?

    • It converts acetylcholine into dopamine, which changes the signal sent to the muscle fibres
    • It increases the speed of action potentials in motor neurones, which speeds up the contraction of muscles
    • It prevents acetylcholine from activating receptors at the neuromuscular junction, causing muscle relaxation
    • It stimulates muscle contraction continuously, since it acts as an agonist for acetylcholine receptors

17. Which pair correctly matches a drug type with its action at the synapse?

    • Agonist: blocks the receptor so the natural transmitter cannot bind
    • Antagonist: mimics neurotransmitter and stimulates the receptor in the postsynaptic membrane
    • Reuptake inhibitor: blocks transporter that removes neurotransmitter from the cleft
    • Enzyme inhibitor: increases release of neurotransmitter from the presynaptic knob

18. A drug that increases neurotransmitter release has an effect on the frequency of action potentials in the postsynaptic neurone. Which statement is most consistent?

    • Frequency is unaffected, since the action potential always has the same size and timing regardless of stimulus
    • Frequency falls because release is increased, since more transmitter shuts down the postsynaptic neurone
    • Frequency is independent of neurotransmitter, since the frequency is set entirely by the myelin sheath
    • Frequency may rise if the postsynaptic neurone reaches threshold more often

19. Which evaluation is most appropriate for the claim that a drug that blocks reuptake is always safe because it only uses the body's natural chemicals?

    • Incorrect, because raising a natural chemical above normal levels can still cause harm
    • Correct, because drugs never affect synapses, so any drug is safe provided the chemical is natural
    • Correct, because natural chemicals are always safe in any amount, so no monitoring is needed for these drugs
    • Incorrect, because drugs cannot be natural, so the claim has no meaning for any drug used in medicine

20. A postsynaptic response measures 6 mV with the natural neurotransmitter and 9 mV with a drug agonist. By what percentage is the response greater with the drug?

    • 50 per cent, found by taking the increase of 3 mV as a share of the natural response of 6 mV
    • 33 per cent, found by taking the increase of 3 mV as a share of the drug response of 9 mV
    • 3 per cent, found by taking the increase of 3 mV as a share of 100 mV
    • 9 per cent, found by taking the drug response of 9 mV as a share of 100 mV

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